START-INFO-DIR-ENTRY
* AutoGen: (autogen).         The Automated Program Generator
END-INFO-DIR-ENTRY

This file documents  Version 5.5

AutoGen copyright (C) 1992-2002 Bruce Korb AutoOpts copyright (C)
1992-2002 Bruce Korb snprintfv copyright (C) 1999-2000 Gary V. Vaughan

AutoGen is free software.

You may redistribute it and/or modify it under the terms of the GNU
General Public License, as published by the Free Software Foundation;
either version 2, or (at your option) any later version.

AutoGen is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with AutoGen.  See the file "COPYING".  If not, write to:  The
Free Software Foundation, Inc.,            59 Temple Place - Suite
330,            Boston,  MA  02111-1307, USA.

The Automated Program Generator
*******************************

This file documents AutoGen version 5.5.  It is a tool designed for
generating program files that contain repetitive text with varied
substitutions.  This document is very long because it is intended as
a reference document.  For a quick start example, *Note Example
Usage::.  For a simple example of Automated Option processing, *Note
Quick Start::.  For a full list of the Automated Option features,
*Note Features::.

This edition documents version 5.5, March 2003.

Introduction
************

AutoGen is a tool designed for generating program files that contain
repetitive text with varied substitutions.  Its goal is to simplify
the maintenance of programs that contain large amounts of repetitious
text.  This is especially valuable if there are several blocks of
such text that must be kept synchronized in parallel tables.

One common example is the problem of maintaining the code required for
processing program options.  Processing options requires a minimum of
four different constructs be kept in proper order in different places
in your program.  You need at least:

  1. The flag character in the flag string,

  2. code to process the flag when it is encountered,

  3. a global state variable or two, and

  4. a line in the usage text.

You will need more things besides this if you choose to implement long
option names, rc/ini file processing, environment variables and so on.
All of this can be done mechanically; with the proper templates and
this program.  In fact, it has already been done and AutoGen itself
uses it *Note AutoOpts::.  For a simple example of Automated Option
processing, *Note Quick Start::.  For a full list of the Automated
Option features, *Note Features::.

The Purpose of AutoGen
======================

The idea of this program is to have a text file, a template if you
will, that contains the general text of the desired output file.
That file includes substitution expressions and sections of text that
are replicated under the control of separate definition files.

AutoGen was designed with the following features:

  1. The definitions are completely separate from the template.  By
     completely isolating the definitions from the template it
     greatly increases the flexibility of the template
     implementation.  A secondary goal is that a template user only
     needs to specify those data that are necessary to describe his
     application of a template.

  2. Each datum in the definitions is named.  Thus, the definitions
     can be rearranged, augmented and become obsolete without it
     being necessary to go back and clean up older definition files.
     Reduce incompatibilities!

  3. Every definition name defines an array of values, even when
     there is only one entry.  These arrays of values are used to
     control the replication of sections of the template.

  4. There are named collections of definitions.  They form a nested
     hierarchy.  Associated values are collected and associated with
     a group name.  These associated data are used collectively in
     sets of substitutions.

  5. The template has special markers to indicate where substitutions
     are required, much like the `${VAR}' construct in a shell `here
     doc'.  These markers are not fixed strings.  They are specified
     at the start of each template.  Template designers know best
     what fits into their syntax and can avoid marker conflicts.

     We did this because it is burdensome and difficult to avoid
     conflicts using either M4 tokenizaion or C preprocessor
     substitution rules.  It also makes it easier to specify
     expressions that transform the value.  Of course, our
     expressions are less cryptic than the shell methods.

  6. These same markers are used, in conjunction with enclosed
     keywords, to indicate sections of text that are to be skipped
     and for sections of text that are to be repeated.  This is a
     major improvement over using C preprocessing macros.  With the C
     preprocessor, you have no way of selecting output text because
     it is an unvarying, mechanical substitution process.

  7. Finally, we supply methods for carefully controlling the output.
     Sometimes, it is just simply easier and clearer to compute some
     text or a value in one context when its application needs to be
     later.  So, functions are available for saving text or values
     for later use.

A Simple Example
================

This is just one simple example that shows a few basic features.  If
you are interested, you also may run "make check" with the `VERBOSE'
enviornment variable set and see a number of other examples in the
`agen5/test/testdir' directory.

Assume you have an enumeration of names and you wish to associate some
string with each name.  Assume also, for the sake of this example,
that it is either too complex or too large to maintain easily by hand.
We will start by writing an abbreviated version of what the result is
supposed to be.  We will use that to construct our output templates.

In a header file, `list.h', you define the enumeration and the global
array containing the associated strings:

     typedef enum {
             IDX_ALPHA,
             IDX_BETA,
             IDX_OMEGA }  list_enum;
     
     extern const char* az_name_list[ 3 ];

Then you also have `list.c' that defines the actual strings:

     #include "list.h"
     const char* az_name_list[] = {
             "some alpha stuff",
             "more beta stuff",
             "final omega stuff" };

First, we will define the information that is unique for each
enumeration name/string pair.  This would be placed in a file named,
`list.def', for example.

     autogen definitions list;
     list = { list_element = alpha;
              list_info    = "some alpha stuff"; };
     list = { list_info    = "more beta stuff";
              list_element = beta; };
     list = { list_element = omega;
              list_info    = "final omega stuff"; };

The `autogen definitions list;' entry defines the file as an AutoGen
definition file that uses a template named `list'.  That is followed
by three `list' entries that define the associations between the
enumeration names and the strings.  The order of the differently named
elements inside of list is unimportant.  They are reversed inside of
the `beta' entry and the output is unaffected.

Now, to actually create the output, we need a template or two that
can be expanded into the files you want.  In this program, we use a
single template that is capable of multiple output files.  The
definitions above refer to a `list' template, so it would normally be
named, `list.tpl'.

It looks something like this.  (For a full description, *Note
Template File::.)

     [+ AutoGen5 template h c +]
     [+ CASE (suffix) +][+
        ==  h  +]
     typedef enum {[+
        FOR list "," +]
             IDX_[+ (string-upcase! (get "list_element")) +][+
        ENDFOR list +] }  list_enum;
     
     extern const char* az_name_list[ [+ (count "list") +] ];
     [+
     
        ==  c  +]
     #include "list.h"
     const char* az_name_list[] = {[+
       FOR list "," +]
             "[+list_info+]"[+
       ENDFOR list +] };[+
     
     ESAC +]

The `[+ AutoGen5 template h c +]' text tells AutoGen that this is an
AutoGen version 5 template file; that it is to be processed twice;
that the start macro marker is `[+'; and the end marker is `+]'.  The
template will be processed first with a suffix value of `h' and then
with `c'.  Normally, the suffix values are appended to the
`base-name' to create the output file name.

The `[+ == h +]' and `[+ == c +]' `CASE' selection clauses select
different text for the two different passes.  In this example, the
output is nearly disjoint and could have been put in two separate
templates.  However, sometimes there are common sections and this is
just an example.

The `[+FOR list "," +]' and `[+ ENDFOR list +]' clauses delimit a
block of text that will be repeated for every definition of `list'.
Inside of that block, the definition name-value pairs that are
members of each `list' are available for substitutions.

The remainder of the macros are expressions.  Some of these contain
special expression functions that are dependent on AutoGen named
values; others are simply Scheme expressions, the result of which
will be inserted into the output text.  Other expressions are names
of AutoGen values.  These values will be inserted into the output
text.  For example, `[+list_info+]' will result in the value
associated with the name `list_info' being inserted between the
double quotes and `(string-upcase! (get "list_element"))' will first
"get" the value associated with the name `list_element', then change
the case of all the letters to upper case.  The result will be
inserted into the output document.

If you have compiled AutoGen, you can copy out the template and
definitions as described above and run `autogen list.def'.  This will
produce exactly the hypothesized desired output.

One more point, too.  Lets say you decided it was too much trouble to
figure out how to use AutoGen, so you created this enumeration and
string list with thousands of entries.  Now, requirements have
changed and it has become necessary to map a string containing the
enumeration name into the enumeration number.  With AutoGen, you just
alter the template to emit the table of names.  It will be guaranteed
to be in the correct order, missing none of the entries.  If you want
to do that by hand, well, good luck.

csh/zsh caveat
==============

AutoGen tries to use your normal shell so that you can supply shell
code in a manner you are accustomed to using.  If, however, you use
csh or zsh, you cannot do this.  Csh is sufficiently difficult to
program that it is unsupported.  Zsh, though largely programmable,
also has some anomolies that make it incompatible with AutoGen usage.
Therefore, when invoking AutoGen from these environments, you must
be certain to set the SHELL environment variable to a Bourne-derived
shell.  e.g., sh, ksh or bash.

Any shell you choose for your own scripts need to follow these basic
requirements:

  1. It handles `trap $sig ":"' without output to standard out.  This
     is done when the server shell is first started.  If your shell
     does not handle this, then it may be able to by loading
     functions from its start up files.

  2. At the beginning of each scriptlet, the command `\\cd $PWD' is
     inserted.  This ensures that `cd' is not aliased to something
     peculiar and each scriptlet starts life in the execution
     directory.

  3. At the end of each scriptlet, the command `echo mumble' is
     appended.  The program you use as a shell must emit the single
     argument `mumble' on a line by itself.

A User's Perspective
====================

Alexandre wrote:
>
> I'd appreciate opinions from others about advantages/disadvantages of
> each of these macro packages.

I am using AutoGen in my pet project, and find one of its best points
to be that it separates the operational data from the implementation.

Indulge me for a few paragraphs, and all will be revealed: In the
manual, Bruce cites the example of maintaining command line flags
inside the source code; traditionally spreading usage information,
flag names, letters and processing across several functions (if not
files).  Investing the time in writing a sort of boiler plate (a
template in AutoGen terminology) pays by moving all of the option
details (usage, flags names etc.) into a well structured table (a
definition file if you will),  so that adding a new command line
option becomes a simple matter of adding a set of details to the
table.

So far so good!  Of course, now that there is a template, writing all
of that tedious optargs processing and usage functions is no longer an
issue.  Creating a table of the options needed for the new project and
running AutoGen generates all of the option processing code in C
automatically from just the tabular data.  AutoGen in fact already
ships with such a template... AutoOpts.

One final consequence of the good separation in the design of AutoGen
is that it is retargetable to a greater extent.  The
egcs/gcc/fixinc/inclhack.def can equally be used (with different
templates) to create a shell script (inclhack.sh) or a c program
(fixincl.c).

This is just the tip of the iceberg.  AutoGen is far more powerful
than these examples might indicate, and has many other varied uses.
I am certain Bruce or I could supply you with many and varied
examples, and I would heartily recommend that you try it for your
project and see for yourself how it compares to m4.

As an aside, I would be interested to see whether someone might be
persuaded to rationalise autoconf with AutoGen in place of m4...  Ben,
are you listening?  autoconf-3.0! `kay?  =)O|

Sincerely,
        Gary V. Vaughan

AutoGen Definitions File
************************

This chapter describes the syntax and semantics of the AutoGen
definition file.  In order to instantiate a template, you normally
must provide a definitions file that identifies itself and contains
some value definitions.  Consequently, we keep it very simple.  For
"advanced" users, there are preprocessing directives and comments that
may be used as well.

The definitions file is used to associate values with names.  Every
value is implicitly an array of values, even if there is only one
value.  Values may be either simple strings or compound collections of
name-value pairs.  An array may not contain both simple and compound
members.  Fundamentally, it is as simple as:

     prog_name = "autogen";
     flag = {
         name      = templ_dirs;
         value     = L;
         descrip   = "Template search directory list";
     };

For purposes of commenting and controlling the processing of the
definitions, C-style comments and most C preprocessing directives are
honored.  The major exception is that the `#if' directive is ignored,
along with all following text through the matching `#endif'
directive.  The C preprocessor is not actually invoked, so C macro
substitution is *not* performed.

The Identification Definition
=============================

The first definition in this file is used to identify it as a AutoGen
file.  It consists of the two keywords, `autogen' and `definitions'
followed by the default template name and a terminating semi-colon
(`;').  That is:

             AutoGen Definitions TEMPLATE-NAME;

Note that, other than the name TEMPLATE-NAME, the words `AutoGen' and
`Definitions' are searched for without case sensitivity.  Most
lookups in this program are case insensitive.

Also, if the input contains more identification definitions, they
will be ignored.  This is done so that you may include (*note
Directives::) other definition files without an identification
conflict.

AutoGen uses the name of the template to find the corresponding
template file.  It searches for the file in the following way,
stopping when it finds the file:

  1. It tries to open `./TEMPLATE-NAME'.  If it fails,

  2. it tries `./TEMPLATE-NAME.tpl'.

  3. It searches for either of these files in the directories listed
     in the templ-dirs command line option.

If AutoGen fails to find the template file in one of these places, it
prints an error message and exits.

Named Definitions
=================

Any name may have multiple values associated with it in the definition
file.  If there is more than one instance, the *only* way to expand
all of the copies of it is by using the FOR (*note FOR::) text
function on it, as described in the next chapter.

There are two kinds of definitions, `simple' and `compound'.  They
are defined thus (*note Full Syntax::):

     compound_name '=' '{' definition-list '}' ';'
     
     simple_name '=' string ';'
     
     no_text_name ';'

`No_text_name' is a simple definition with a shorthand empty string
value.  The string values for definitions may be specified in any of
several formation rules.

Definition List
---------------

`definition-list' is a list of definitions that may or may not
contain nested compound definitions.  Any such definitions may *only*
be expanded within a `FOR' block iterating over the containing
compound definition.  *Note FOR::.

Here is, again, the example definitions from the previous chapter,
with three additional name value pairs.  Two with an empty value
assigned (FIRST and LAST), and a "global" GROUP_NAME.

     autogen definitions list;
     group_name = example;
     list = { list_element = alpha;  first;
              list_info    = "some alpha stuff"; };
     list = { list_info    = "more beta stuff";
              list_element = beta; };
     list = { list_element = omega;  last;
              list_info    = "final omega stuff"; };

Double Quote String
-------------------

The string follows the C-style escaping (`\', `\n', `\f', `\v',
etc.), plus octal character numbers specified as `\ooo'.  The
difference from "C" is that the string may span multiple lines.  Like
ANSI "C", a series of these strings, possibly intermixed with single
quote strings, will be concatenated together.

Single Quote String
-------------------

This is similar to the shell single-quote string.  However, escapes
`\' are honored before another escape, single quotes `'' and hash
characters `#'.  This latter is done specifically to disambiguate
lines starting with a hash character inside of a quoted string.  In
other words,

     fumble = '
     #endif
     ';

could be misinterpreted by the definitions scanner, whereas this
would not:

     fumble = '
     \#endif
     ';

As with the double quote string, a series of these, even intermixed
with double quote strings, will be concatenated together.

Shell Output String
-------------------

This is assembled according to the same rules as the double quote
string, except that there is no concatenation of strings and the
resulting string is written to a shell server process.  The
definition takes on the value of the output string.

NB  The text is interpreted by a server shell.  There may be left
over state from previous ``' processing and it may leave state for
subsequent processing.  However, a `cd' to the original directory is
always issued before the new command is issued.

An Unquoted String
------------------

A simple string that does not contain white space may be left
unquoted.  The string must not contain any of the characters special
to the definition text (i.e. `"', `#', `'', `(', `)', `,', `;', `<',
`=', `>', `[', `]', ``', `{', or `}').  This list is subject to
change, but it will never contain underscore (`_'), period (`.'),
slash (`/'), colon (`:'), hyphen (`-') or backslash (`\\').
Basically, if the string looks like it is a normal DOS or UNIX file
or variable name, and it is not one of two keywords (`autogen' or
`definitions') then it is OK to not quote it, otherwise you should.

Scheme Result String
--------------------

A scheme result string must begin with an open parenthesis `('.  The
scheme expression will be evaluated by Guile and the value will be
the result.  The AutoGen expression functions are *dis*abled at this
stage, so do not use them.

A Here String
-------------

A `here string' is formed in much the same way as a shell here doc.
It is denoted with a doubled less than character and, optionally, a
hyphen.  This is followed by optional horizontal white space and an
ending marker-identifier.  This marker must follow the syntax rules
for identifiers.  Unlike the shell version, however, you must not
quote this marker.  The resulting string will start with the first
character on the next line and continue up to but not including the
newline that precedes the line that begins with the marker token.  No
backslash or any other kind of processing is done on this string.
The characters are copied directly into the result string.

Here are two examples:
     str1 = <<-  STR_END
             $quotes = " ' `
             STR_END;
     
     str2 = <<   STR_END
             $quotes = " ' `
             STR_END;
     STR_END;
The first string contains no new line characters.  The first
character is the dollar sign, the last the back quote.

The second string contains one new line character.  The first
character is the tab character preceeding the dollar sign.  The last
character is the semicolon after the `STR_END'.  That `STR_END' does
not end the string because it is not at the beginning of the line.
In the preceeding case, the leading tab was stripped.

Concatenated Strings
--------------------

If single or double quote characters are used, then you also have the
option, a la ANSI-C syntax, of implicitly concatenating a series of
them together, with intervening white space ignored.

NB  You *cannot* use directives to alter the string content.  That is,

     str = "fumble"
     #ifdef LATER
           "stumble"
     #endif
           ;

will result in a syntax error.  The preprocessing directives are not
carried out by the C preprocessor.  However,

     str = '"fumble\n"
     #ifdef LATER
     "     stumble\n"
     #endif
     ';

*Will* work.  It will enclose the `#ifdef LATER' and `#endif' in the
string.  But it may also wreak havoc with the definition processing
directives.  The hash characters in the first column should be
disambiguated with an escape `\' or join them with previous lines:
`"fumble\n#ifdef LATER...'.

Assigning an Index to a Definition
==================================

In AutoGen, every name is implicitly an array of values.  When
assigning values, they are usually implicitly assiged to the next
highest slot.  They can also be specified explicitly:

     mumble[9] = stumble;
     mumble[0] = grumble;

If, subsequently, you assign a value to `mumble' without an index,
its index will be `10', not `1'.  If indexes are specified, they must
not cause conflicts.

`#define'-d names may also be used for index values.  This is
equivalent to the above:

     #define FIRST 0
     #define LAST  9
     mumble[LAST]  = stumble;
     mumble[FIRST] = grumble;

All values in a range do *not* have to be filled in.  If you leave
gaps, then you will have a sparse array.  This is fine (*note FOR::).
You have your choice of iterating over all the defined values, or
iterating over a range of slots.  This:

     [+ FOR mumble +][+ ENDFOR +]

iterates over all and only the defined entries, whereas this:

     [+ FOR mumble (for-by 1) +][+ ENDFOR +]

will iterate over all 10 "slots".  Your template will likely have to
contain something like this:

     [+ IF (exist? (sprintf "mumble[%d]" (for-index))) +]

or else "mumble" will have to be a compound value that, say, always
contains a "grumble" value:

     [+ IF (exist? "grumble") +]

Dynamic Text
============

There are several methods for including dynamic content inside a
definitions file.  Three of them are mentioned above (*Note
shell-generated:: and *note scheme-generated::) in the discussion of
string formation rules.  Another method uses the `#shell' processing
directive.  It will be discussed in the next section (*note
Directives::).  Guile/Scheme may also be used to yield to create
definitions.

When the Scheme expression is preceeded by a backslash and single
quote, then the expression is expected to be an alist of names and
values that will be used to create AutoGen definitions.

This method can be be used as follows:

     \'( (name  (value-expression))
         (name2 (another-expr))  )

This is entirely equivalent to:

     name  = (value-expression);
     name2 = (another-expr);

Under the covers, the expression gets handed off to a Guile function
named `alist->autogen-def' in an expression that looks like this:

     (alist->autogen-def
         ( (name (value-expression))  (name2 (another-expr)) ) )

Controlling What Gets Processed
===============================

Definition processing directives can *only* be processed if the '#'
character is the first character on a line.  Also, if you want a '#'
as the first character of a line in one of your string assignments,
you should either escape it by preceding it with a backslash `\', or
by embedding it in the string as in `"\n#"'.

All of the normal C preprocessing directives are recognized, though
several are ignored.  There is also an additional `#shell' -
`#endshell' pair.  Another minor difference is that AutoGen
directives must have the hash character (`#') in column 1.

The final tweak is that `#!' is treated as a comment line.  Using
this feature, you can use:  `#! /usr/local/bin/autogen' as the first
line of a definitons file, set the mode to executable and "run" the
definitions file as if it were a direct invocation of AutoGen.  This
was done for its hack value.

The ignored directives are: `#assert', `#ident', `#pragma',  and
`#if'.  Note that when ignoring the `#if' directive, all intervening
text through its matching `#endif' is also ignored, including the
`#else' clause.

The AutoGen directives that affect the processing of definitions are:

`#define name [ <text> ]'
     Will add the name to the define list as if it were a DEFINE
     program argument.  Its value will be the first non-whitespace
     token following the name.  Quotes are *not* processed.

     After the definitions file has been processed, any remaining
     entries in the define list will be added to the environment.

`#elif'
     This must follow an `#if' otherwise it will generate an error.
     It will be ignored.

`#else'
     This must follow an `#if', `#ifdef' or `#ifndef'.  If it follows
     the `#if', then it will be ignored.  Otherwise, it will change
     the processing state to the reverse of what it was.

`#endif'
     This must follow an `#if', `#ifdef' or `#ifndef'.  In all cases,
     this will resume normal processing of text.

`#endshell'
     Ends the text processed by a command shell into autogen
     definitions.

`#error [ <descriptive text> ]'
     This directive will cause AutoGen to stop processing and exit
     with a status of EXIT_FAILURE.

`#if [ <ignored conditional expression> ]'
     `#if' expressions are not analyzed.  *Everything* from here to
     the matching `#endif' is skipped.

`#ifdef name-to-test'
     The definitions that follow, up to the matching `#endif' will be
     processed only if there is a corresponding `-Dname' command line
     option.

`#ifndef name-to-test'
     The definitions that follow, up to the matching `#endif' will be
     processed only if there is *not* a corresponding `-Dname'
     command line option or there was a canceling `-Uname' option.

`#include unadorned-file-name'
     This directive will insert definitions from another file into
     the current collection.  If the file name is adorned with double
     quotes or angle brackets (as in a C program), then the include
     is ignored.

`#line'
     Alters the current line number and/or file name.  You may wish to
     use this directive if you extract definition source from other
     files.  `getdefs' uses this mechanism so AutoGen will report the
     correct file and approximate line number of any errors found in
     extracted definitions.

`#option opt-name [ <text> ]'
     This directive will pass the option name and associated text to
     the AutoOpts optionLoadLine routine (*note optionLoadLine::).
     The option text may span multiple lines by continuing them with
     a backslash.  The backslash/newline pair will be replaced with
     two space characters.  This directive may be used to set a
     search path for locating template files For example, this:

          #option templ-dirs $ENVVAR/dirname

     will direct autogen to use the `ENVVAR' environment variable to
     find a directory named `dirname' that (may) contain templates.
     Since these directories are searched in most recently supplied
     first order, search directories supplied in this way will be
     searched before any supplied on the command line.

`#shell'
     Invokes `$SHELL' or `/bin/sh' on a script that should generate
     AutoGen definitions.  It does this using the same server process
     that handles the back-quoted ``' text.  *CAUTION*  let not your
     `$SHELL' be `csh'.

`#undef name-to-undefine'
     Will remove any entries from the define list that match the
     undef name pattern.

Pre-defined Names
=================

When AutoGen starts, it tries to determine several names from the
operating environment and put them into environment variables for use
in both `#ifdef' tests in the definitions files and in shell scripts
with environment variable tests.  `__autogen__' is always defined.
For other names, AutoGen will first try to use the POSIX version of
the `sysinfo(2)' system call.  Failing that, it will try for the POSIX
`uname(2)' call.  If neither is available, then only "`__autogen__'"
will be inserted into the environment.  In all cases, the associated
names are converted to lower case, surrounded by doubled underscores
and non-symbol characters are replaced with underscores.

With Solaris on a sparc platform, `sysinfo(2)' is available.  The
following strings are used:

   * `SI_SYSNAME' (e.g., "__sunos__")

   * `SI_HOSTNAME' (e.g., "__ellen__")

   * `SI_ARCHITECTURE' (e.g., "__sparc__")

   * `SI_HW_PROVIDER' (e.g., "__sun_microsystems__")

   * `SI_PLATFORM' (e.g., "__sun_ultra_5_10__")

   * `SI_MACHINE' (e.g., "__sun4u__")

For Linux and other operating systems that only support the
`uname(2)' call, AutoGen will use these values:

   * `sysname' (e.g., "__linux__")

   * `machine' (e.g., "__i586__")

   * `nodename' (e.g., "__bach__")

By testing these pre-defines in my definitions, you can select pieces
of the definitions without resorting to writing shell scripts that
parse the output of `uname(1)'.  You can also segregate real C code
from autogen definitions by testing for "`__autogen__'".

     #ifdef __bach__
       location = home;
     #else
       location = work;
     #endif

Commenting Your Definitions
===========================

The definitions file may contain C and C++ style comments.

     /*
      *  This is a comment.  It continues for several lines and closes
      *  when the characters '*' and '/' appear together.
      */
     // this comment is a single line comment

What it all looks like.
=======================

This is an extended example:

     autogen definitions `template-name';
     /*
      *  This is a comment that describes what these
      *  definitions are all about.
      */
     global = "value for a global text definition.";
     
     /*
      *  Include a standard set of definitions
      */
     #include standards.def
     
     a_block = {
         a_field;
         a_subblock = {
             sub_name  = first;
             sub_field = "sub value.";
         };
     
     #ifdef FEATURE
         a_subblock = {
             sub_name  = second;
         };
     #endif
     
     };

YACC Language Grammar
=====================

The preprocessing directives and comments are not part of the
grammar.  They are handled by the scanner/lexer.  The following was
extracted directly from the defParse.y source file:

     definitions : identity def_list TK_END
                     { $$ = (YYSTYPE)(rootDefCtx.pDefs = (tDefEntry*)$2); }
                 | identity TK_END
                     { $$ = makeEmptyDefs(); }
                 ;
     
     def_list    : definition           { $$ = $1; }
                 | definition def_list  { $$ = addSibMacro( $1, $2 ); }
                 | identity   def_list  { $$ = $2; }
                 ;
     
     identity    : TK_AUTOGEN TK_DEFINITIONS filename ';'
                     { $$ = identify( $3 ); }
                 ;
     
     definition  : value_name ';'
                     { $$ = makeMacro( $1, (YYSTYPE)"", VALTYP_TEXT ); }
     
                 | value_name '=' text_list ';'
                     { $$ = makeMacroList( $1, $3, VALTYP_TEXT ); }
     
                 | value_name '=' block_list ';'
                     { $$ = makeMacroList( $1, $3, VALTYP_BLOCK ); }
                 ;
     
     text_list   : anystring                { $$ = startList( $1 ); }
                 | anystring ',' text_list  { $$ = appendList( $1, $3 ); }
                 ;
     
     block_list  : def_block                { $$ = startList( $1 ); }
                 | def_block ',' block_list { $$ = appendList( $1, $3 ); }
                 ;
     
     def_block   : '{' def_list '}'         { $$ = $2; } ;
     
     anystring   : filename      { $$ = $1; }
                 | TK_NUMBER     { $$ = $1; } ;
     
     filename    : TK_OTHER_NAME { $$ = $1; }
                 | TK_STRING     { $$ = $1; }
                 | TK_VAR_NAME   { $$ = $1; } ;
     
     value_name  : TK_VAR_NAME
                     { $$ = findPlace( (YYSTYPE)$1, (YYSTYPE)NULL ); }
     
                 | TK_VAR_NAME '[' TK_NUMBER ']'
                     { $$ = findPlace( (YYSTYPE)$1, (YYSTYPE)$3 ); }
     
                 | TK_VAR_NAME '[' TK_VAR_NAME ']'
                     { $$ = findPlace( (YYSTYPE)$1, (YYSTYPE)$3 ); }
                 ;

Alternate Definition Forms
==========================

There are several methods for supplying data values for templates.

`no definitions'
     It is entirely possible to write a template that does not depend
     upon external definitions.  Such a template would likely have an
     unvarying output, but be convenient nonetheless because of an
     external library of either AutoGen or Scheme functions, or both.
     This can be accommodated by providing the `--override-tpl' and
     `--no-definitions' options on the command line.  *Note autogen
     Invocation::.

`CGI'
     AutoGen behaves as a CGI server if the definitions input is from
     stdin and the environment variable `REQUEST_METHOD' is defined
     and set to either "GET" or "POST", *Note AutoGen CGI::.
     Obviously, all the values are constrained to strings because
     there is no way to represent nested values.

`XML'
     AutoGen comes with a program named, `xml2ag'.  Its output can
     either be redirected to a file for later use, or the program can
     be used as an AutoGen wrapper.  *Note xml2ag Invocation::.

     The introductory template example (*note Example Usage::) can be
     rewritten in XML as follows:

          <EXAMPLE  template="list.tpl">
          <LIST list_element="alpha"
                list_info="some alpha stuff"/>
          <LIST list_info="more beta stuff"
                list_element="beta"/>
          <LIST list_element="omega"
                list_info="final omega stuff"/>
          </EXAMPLE>

     A more XML-normal form might look like this:
          <EXAMPLE  template="list.tpl">
          <LIST list_element="alpha">some alpha stuff</LIST>
          <LIST list_element="beta" >more beta stuff</LIST>
          <LIST list_element="omega">final omega stuff</LIST>
          </EXAMPLE>

     but you would have to change the template `list_info' references
     into `text' references.

`standard AutoGen definitions'
     Of course.  :-)


AutoGen Template
****************

The AutoGen template file defines the content of the output text.  It
is composed of two parts.  The first part consists of a pseudo macro
invocation and commentary.  It is followed by the template proper.

This pseudo macro is special.  It is used to identify the file as a
AutoGen template file, fixing the starting and ending marks for the
macro invocations in the rest of the file, specifying the list of
suffixes to be generated by the template and, optionally, the shell
to use for processing shell commands embedded in the template.

AutoGen-ing a file consists of copying text from the template to the
output file until a start macro marker is found.  The text from the
start marker to the end marker constitutes the macro text.  AutoGen
macros may cause sections of the template to be skipped or processed
several times.  The process continues until the end of the template is
reached.  The process is repeated once for each suffix specified in
the pseudo macro.

This chapter describes the format of the AutoGen template macros and
the usage of the AutoGen native macros.  Users may augment these by
defining their own macros.  *Note DEFINE::.

Format of the Pseudo Macro
==========================

The pseudo macro is used to tell AutoGen how to process a template.
It tells autogen:

  1. The punctuation characters used to demarcate the start of a
     macro.  It may be up to seven characters long and must be the
     first non-whitespace characters in the file.

  2. That start marker must be immediately followed by the marker
     strings "AutoGen5" and then "template", though capitalization is
     not important.

The next several components may be intermingled:

  3. Zero, one or more suffix specifications tell AutoGen how many
     times to process the template file.  No suffix specifications
     mean that it is to be processed once and that the generated text
     is to be written to stdout.  The current suffix for each pass
     can be determined with the `(suffix)' scheme function (*note SCM
     suffix::).

     The suffix specification consists of a sequence of POSIX
     compliant file name characters and, optionally, an equal sign
     and a file name "printf"-style formatting string.  Two string
     arguments are allowed for that string: the base name of the
     definition file and the current suffix (that being the text to
     the left of the equal sign).  (Note:  "POSIX compliant file name
     characters" consist of alphanumerics plus the period (`.'),
     hyphen (`-') and underscore (`_') characters.)

  4. Comment lines:  blank lines, lines starting with a hash mark
     [`#']), and edit mode comments (text between pairs of `-*-'
     strings).

  5. Scheme expressions may be inserted in order to make configuration
     changes before template processing begins.  It is used, for
     example, to allow the template writer to specify the shell
     program that must be used to interpret the shell commands in the
     template.  It can have no effect on any shell commands in the
     definitions file, as that file will have been processed by the
     time the pseudo macro is interpreted.

          (setenv "SHELL" "/bin/sh")

     This is extremely useful to ensure that the shell used is the
     one the template was written to use.  By default, AutoGen
     determines the shell to use by user preferences.  Sometimes,
     that can be the "csh", though.

     The scheme expression can also be used to save a pre-existing
     output file for later text extraction (*note SCM extract::).

          (shellf "mv -f %1$s.c %1$s.sav" (base-name))

  6. Finally, the end-macro marker must be last.  It must not begin
     with a POSIX file name character, and if it begins with an equal
     sign, then it must be separated from any suffix specification by
     white space.

It is generally a good idea to use some sort of opening bracket in
the starting macro and closing bracket in the ending macro  (e.g.
`{', `(', `[', or even `<' in the starting macro).  It helps both
visually and with editors capable of finding a balancing parenthesis.
The closing marker may *not* begin with an open parenthesis, as that
is used to enclose a scheme expression.

It is also helpful to avoid using the comment marker (`#'); the
POSIXly acceptable file name characters period (`.'), hyphen (`-')
and underscore (`_'); and finally, it is advisable to avoid using any
of the quote characters  double, single or back-quote.  But there is
no special check for any of these advisories.

As an example, assume we want to use `[+' and `+]' as the start and
end macro markers, and we wish to produce a `.c' and a `.h' file,
then the first macro invocation will look something like this:

     [+ AutoGen5 template -*- Mode: emacs-mode-of-choice -*-
     h=chk-%s.h
     c
     # make sure we don't use csh:
     (setenv "SHELL" "/bin/sh")  +]

The template proper starts after the pseudo-macro.  The starting
character is either the first non-whitespace character or the first
character after the newline that follows the end macro marker.

Naming a value
==============

When an AutoGen value is specified in a template, it is specified by
name.  The name may be a simple name, or a compound name of several
components.  Since each named value in AutoGen is implicitly an array
of one or more values, each component may have an index associated
with it.

It looks like this:

     comp-name-1 . comp-name-2 [ 2 ]

Note that if there are multiple components to a name, each component
name is separated by a dot (`.').  Indexes follow a component name,
enclosed in square brackets (`[' and `]').  The index may be either
an integer or an integer-valued define name.  The first component of
the name is searched for in the current definition level.  If not
found, higher levels will be searched until either a value is found,
or there are no more definition levels.  Subsequent components of the
name must be found within the context of the newly-current definition
level.  Also, if the named value is prefixed by a dot (`.'), then the
value search is started in the current context only.  No higher
levels are searched.

If someone rewrites this, I'll incorporate it.  :-)

Macro Expression Syntax
=======================

AutoGen has two types of expressions:  full expressions and basic
ones.  A full AutoGen expression can appear by itself, or as the
argument to certain AutoGen built-in macros:  CASE, IF, ELIF, INCLUDE,
INVOKE (explicit invocation, *note INVOKE::), and WHILE.  If it
appears by itself, the result is inserted into the output.  If it is
an argument to one of these macros, the macro code will act on it
sensibly.

You are constrained to basic expressions only when passing arguments
to user defined macros, *Note DEFINE::.

The syntax of a full AutoGen expression is:

     [[ <apply-code> ] <value-name> ] [ <basic-expr-1> [ <basic-expr-2> ]]

How the expression is evaluated depends upon the presence or absence
of the apply code and value name.  The "value name" is the name of an
AutoGen defined value, or not.  If it does not name such a value, the
expression result is generally the empty string.  All expressions
must contain either a `value-name' or a `basic-expr'.

Apply Code
----------

The "apply code" selected determines the method of evaluating the
expression.  There are five apply codes, including the non-use of an
apply code.

`no apply code'
     This is the most common expression type.  Expressions of this
     sort come in three flavors:

    `<value-name>'
          The result is the value of `value-name', if defined.
          Otherwise it is the empty string.

    `<basic-expr>'
          The result of the basic expression is the result of the
          full expression, *Note basic expression::.

    `<value-name> <basic-expr>'
          If there is a defined value for `value-name', then the
          `basic-expr' is evaluated.  Otherwise, the result is the
          empty string.

`% <value-name> <basic-expr>'
     If `value-name' is defined, use `basic-expr' as a format string
     for sprintf.  Then, if the `basic-expr' is either a back-quoted
     string or a parenthesized expression, then hand the result to the
     appropriate interpreter for further evaluation.  Otherwise, for
     single and double quote strings, the result is the result of the
     sprintf operation.  Naturally, if `value-name' is not defined,
     the result is the empty string.

     For example, assume that `fumble' had the string value,
     `stumble':
          [+ % fumble `printf '%%x\\n' $%s` +]
     This would cause the shell to evaluate "`printf '%x\n'
     $stumble'".  Assuming that the shell variable `stumble' had a
     numeric value, the expression result would be that number, in
     hex.  Note the need for doubled percent characters and
     backslashes.

`? <value-name> <basic-expr-1> <basic-expr-2>'
     Two `basic-expr'-s are required.  If the `value-name' is
     defined, then the first `basic-expr-1' is evaluated, otherwise
     `basic-expr-2' is.

`- <value-name> <basic-expr>'
     Evaluate `basic-expr' only if `value-name' is not defined.

`?% <value-name> <basic-expr-1> <basic-expr-2>'
     This combines the functions of `?' and `%'.  If `value-name' is
     defined, it behaves exactly like `%', above, using
     `basic-expr-1'.  If not defined, then `basic-expr-2' is
     evaluated.

     For example, assume again that `fumble' had the string value,
     `stumble':
          [+ ?% fumble `cat $%s` `pwd` +]
     This would cause the shell to evaluate "`cat $stumble'".  If
     `fumble' were not defined, then the result would be the name of
     our current directory.

Basic Expression
----------------

A basic expression can have one of the following forms:

`'STRING''
     A single quoted string.  Backslashes can be used to protect
     single quotes (`''), hash characters (`#'), or backslashes (`\')
     in the string.  All other characters of STRING are output as-is
     when the single quoted string is evaluated.  Backslashes are
     processed before the hash character for consistency with the
     definition syntax.  It is needed there to avoid preprocessing
     conflicts.

`"STRING"'
     A double quoted string.  This is a cooked text string as in C,
     except that they are not concatenated with adjacent strings.
     Evaluating "`STRING'" will output STRING with all backslash
     sequences interpreted.

``STRING`'
     A back quoted string.  When this expression is evaluated, STRING
     is first interpreted as a cooked string (as in `"STRING"') and
     evaluated as a shell expression by the AutoGen server shell.
     This expression is replaced by the stdout output of the shell.

`(STRING)'
     A parenthesized expression.  It will be passed to the Guile
     interpreter for evaluation and replaced by the resulting value.

     Additionally, other than in the `%' and `?%' expressions, the
     Guile expressions may be introduced with the Guile comment
     character (`;') and you may put a series of Guile expressions
     within a single macro.  They will be implicitly evaluated as if
     they were arguments to the `(begin ...)' expression.  The result
     will be the the result of the last Guile expression evaluated.

AutoGen Scheme Functions
========================

AutoGen uses Guile to interpret Scheme expressions within AutoGen
macros.  All of the normal Guile functions are available, plus several
extensions (*note Common Functions::) have been added to augment the
repertoire of string manipulation functions and manage the state of
AutoGen processing.

This section describes those functions that are specific to AutoGen.
Please take note that these AutoGen specific functions are not loaded
and thus not made available until after the command line options have
been processed and the AutoGen definitions have been loaded.  They
may, of course, be used in Scheme functions that get defined at those
times, but they cannot be invoked.

`ag-function?' - test for function
----------------------------------

Usage:  (ag-function? ag-name)
return SCM_BOOL_T if a specified name is a user-defined AutoGen
macro, otherwise return SCM_BOOL_F.

Arguments:
ag-name - name of AutoGen macro

`base-name' - base output name
------------------------------

Usage:  (base-name)
Returns a string containing the base name of the output file(s).
Generally, this is also the base name of the definitions file.

This Scheme function takes no arguments.

`count' - definition count
--------------------------

Usage:  (count ag-name)
Count the number of entries for a definition.  The input argument
must be a string containing the name of the AutoGen values to be
counted.  If there is no value associated with the name, the result
is an SCM immediate integer value of zero.

Arguments:
ag-name - name of AutoGen value

`def-file' - definitions file name
----------------------------------

Usage:  (def-file)
Get the name of the definitions file.  Returns the name of the source
file containing the AutoGen definitions.

This Scheme function takes no arguments.

`dne' - "Do Not Edit" warning
-----------------------------

Usage:  (dne prefix [ first_prefix ] [ optpfx ])
Generate a "DO NOT EDIT" or "EDIT WITH CARE" warning string.  Which
depends on whether or not the `--writable' command line option was
set.  The first argument is a per-line string prefix.  The optional
second argument is a prefix for the first-line and, in read-only
mode, activates the editor hints.
     -*- buffer-read-only: t -*- vi: set ro:

The warning string also includes information about the template used
to construct the file and the definitions used in its instantiation.

The optional third argument is used when the first argument is
actually an invocation option and the prefix arguments get shifted.
The first argument must be, specifically, "`-d'".  That is used to
signify that the date stamp should not be inserted into the output.

Arguments:
prefix - string for starting each output line
first_prefix - Optional - for the first output line
optpfx - Optional - shifted prefix

`error' - display message and exit
----------------------------------

Usage:  (error message)
The argument is a string that printed out as part of an error
message.  The message is formed from the formatting string:

     DEFINITIONS ERROR in %s line %d for %s:  %s\n

The first three arguments to this format are provided by the routine
and are:  The name of the template file, the line within the template
where the error was found, and the current output file name.

After displaying the message, the current output file is removed and
autogen exits with the EXIT_FAILURE error code.  IF, however, the
argument begins with the number 0 (zero), or the string is the empty
string, then processing continues with the next suffix.

Arguments:
message - message to display before exiting

`exist?' - test for value name
------------------------------

Usage:  (exist? ag-name)
return SCM_BOOL_T iff a specified name has an AutoGen value.  The
name may include indexes and/or member names.  All but the last
member name must be an aggregate definition.  For example:
     (exist? "foo[3].bar.baz")
will yield true if all of the following is true:
There is a member value of either group or string type named `baz'
for some group value `bar' that is a member of the `foo' group with
index `3'.  There may be multiple entries of `bar' within `foo', only
one needs to contain a value for `baz'.

Arguments:
ag-name - name of AutoGen value

`find-file' - locate a file in the search path
----------------------------------------------

Usage:  (find-file file-name [ suffix ])
AutoGen has a search path that it uses to locate template and
definition files.  This function will search the same list for
`file-name', both with and without the `.suffix', if provided.

Arguments:
file-name - name of file with text
suffix - Optional - file suffix to try, too

`first-for?' - detect first iteration
-------------------------------------

Usage:  (first-for? [ for_var ])
Returns SCM_BOOL_T if the named FOR loop (or, if not named, the
current innermost loop) is on the first pass through the data.
Outside of any FOR loop, it returns SCM_UNDEFINED.  *Note FOR::.

Arguments:
for_var - Optional - which for loop

`for-by' - set iteration step
-----------------------------

Usage:  (for-by by)
This function records the "step by" information for an AutoGen FOR
function.  Outside of the FOR macro itself, this function will emit
an error.  *Note FOR::.

Arguments:
by - the iteration increment for the AutoGen FOR macro

`for-from' - set initial index
------------------------------

Usage:  (for-from from)
This function records the initial index information for an AutoGen
FOR function.  Outside of the FOR macro itself, this function will
emit an error.  *Note FOR::.

Arguments:
from - the initial index for the AutoGen FOR macro

`for-index' - get current loop index
------------------------------------

Usage:  (for-index [ for_var ])
Returns the current index for the named FOR loop.  If not named, then
the index for the innermost loop.  Outside of any FOR loop, it
returns SCM_UNDEFINED.  *Note FOR::.

Arguments:
for_var - Optional - which for loop

`for-sep' - set loop separation string
--------------------------------------

Usage:  (for-sep separator)
This function records the separation string that is to be inserted
between each iteration of an AutoGen FOR function.  This is often
nothing more than a comma.  Outside of the FOR macro itself, this
function will emit an error.

Arguments:
separator - the text to insert between the output of each FOR
iteration

`for-to' - set ending index
---------------------------

Usage:  (for-to to)
This function records the terminating value information for an
AutoGen FOR function.  Outside of the FOR macro itself, this function
will emit an error.  *Note FOR::.

Arguments:
to - the final index for the AutoGen FOR macro

`get' - get named value
-----------------------

Usage:  (get ag-name)
Get the first string value associated with the name.  It will always
return either the associated string value, or the empty string.

Arguments:
ag-name - name of AutoGen value

`high-lim' - get highest value index
------------------------------------

Usage:  (high-lim ag-name)
Returns the highest index associated with an array of definitions.
This is generally, but not necessarily, one less than the `count'
value.  (The indexes may be specified, rendering a non-zero based or
sparse array of values.)

This is very useful for specifying the size of a zero-based array of
values where not all values are present.  For example:

     tMyStruct myVals[ [+ (+ 1 (high-lim "my-val-list")) +] ];

Arguments:
ag-name - name of AutoGen value

`last-for?' - detect last iteration
-----------------------------------

Usage:  (last-for? [ for_var ])
Returns SCM_BOOL_T if the named FOR loop (or, if not named, the
current innermost loop) is on the last pass through the data.
Outside of any FOR loop, it returns SCM_UNDEFINED.  *Note FOR::.

Arguments:
for_var - Optional - which for loop

`len' - get count of values
---------------------------

Usage:  (len ag-name)
If the named object is a group definition, then "len" is the same as
"count".  Otherwise, if it is one or more text definitions, then it
is the sum of their string lengths.  If it is a single text
definition, then it is equivalent to `(string-length (get
"ag-name"))'.

Arguments:
ag-name - name of AutoGen value

`low-lim' - get lowest value index
----------------------------------

Usage:  (low-lim ag-name)
Returns the lowest index associated with an array of definitions.

Arguments:
ag-name - name of AutoGen value

`match-value?' - test for matching value
----------------------------------------

Usage:  (match-value? op ag-name test-str)
This function answers the question, "Is there an AutoGen value named
`ag-name' with a value that matches the pattern `test-str' using the
match function `op'?"  Return SCM_BOOL_T iff at least one occurrence
of the specified name has such a value.  The operator can be any
function that takes two string arguments and yields a boolean.  It is
expected that you will use one of the string matching functions
provided by AutoGen.
The value name must follow the same rules as the `ag-name' argument
for `exist?' (*note SCM exist?::).

Arguments:
op - boolean result operator
ag-name - name of AutoGen value
test-str - string to test against

`out-delete' - delete current output file
-----------------------------------------

Usage:  (out-delete)
Remove the current output file.  Cease processing the template for
the current suffix.  It is an error if there are `push'-ed output
files.  Use the `(error "0")' scheme function instead.  *Note output
controls::.

This Scheme function takes no arguments.

`out-depth' - output file stack depth
-------------------------------------

Usage:  (out-depth)
Returns the depth of the output file stack.  *Note output controls::.

This Scheme function takes no arguments.

`out-move' - change name of output file
---------------------------------------

Usage:  (out-move new-name)
Rename current output file.  *Note output controls::.  Please note:
changing the name will not save a temporary file from being deleted.
It may, however, be used on the root output file.

Arguments:
new-name - new name for the current output file

`out-name' - current output file name
-------------------------------------

Usage:  (out-name)
Returns the name of the current output file.  If the current file is
a temporary, unnamed file, then it will scan up the chain until a
real output file name is found.  *Note output controls::.

This Scheme function takes no arguments.

`out-pop' - close current output file
-------------------------------------

Usage:  (out-pop [ disp ])
If there has been a `push' on the output, then close that file and go
back to the previously open file.  It is an error if there has not
been a `push'.  *Note output controls::.

If there is no argument, no further action is taken.  Otherwise, the
argument should be `#t' and the contents of the file are returned by
the function.

Arguments:
disp - Optional - return contents of the file

`out-push-add' - append output to file
--------------------------------------

Usage:  (out-push-add file-name)
Identical to `push-new', except the contents are *not* purged, but
appended to.  *Note output controls::.

Arguments:
file-name - name of the file to append text to

`out-push-new' - purge and create output file
---------------------------------------------

Usage:  (out-push-new [ file-name ])
Leave the current output file open, but purge and create a new file
that will remain open until a `pop' `delete' or `switch' closes it.
The file name is optional and, if omitted, the output will be sent to
a temporary file that will be deleted when it is closed.  *Note
output controls::.

Arguments:
file-name - Optional - name of the file to create

`out-resume' - resume current output file
-----------------------------------------

Usage:  (out-resume suspName)
If there has been a suspended output, then make that output descriptor
current again.  That output must have been suspended with the same tag
name given to this routine as its argument.

Arguments:
suspName - A name tag for reactivating

`out-suspend' - suspend current output file
-------------------------------------------

Usage:  (out-suspend suspName)
If there has been a `push' on the output, then set aside the output
descriptor for later reactiviation with `(out-resume "xxx")'.  The
tag name need not reflect the name of the output file.  In fact, the
output file may be an anonymous temporary file.  You may also change
the tag every time you suspend output to a file, because the tag
names are forgotten as soon as the file has been "resumed".

Arguments:
suspName - A name tag for reactivating

`out-switch' - close and create new output
------------------------------------------

Usage:  (out-switch file-name)
Switch output files - close current file and make the current file
pointer refer to the new file.  This is equivalent to `out-pop'
followed by `out-push-new', except that you may not pop the base
level output file, but you may `switch' it.  *Note output controls::.

Arguments:
file-name - name of the file to create

`set-option' - Set a command line option
----------------------------------------

Usage:  (set-option opt)
The text argument must be an option name followed by any needed
option argument.  Returns SCM_UNDEFINED.

Arguments:
opt - AutoGen option name + its argument

`set-writable' - Make the output file be writable
-------------------------------------------------

Usage:  (set-writable [ set? ])
This function will set the current output file to be writable (or
not).  This is only effective if neither the `--writable' nor
`--not-writable' have been specified.  This state is reset when the
current suffix's output is complete.

Arguments:
set? - Optional - boolean arg, false to make output non-writable

`stack' - make list of AutoGen values
-------------------------------------

Usage:  (stack ag-name)
Create a scheme list of all the strings that are associated with a
name.  They must all be text values or we choke.

Arguments:
ag-name - AutoGen value name

`suffix' - get the current suffix
---------------------------------

Usage:  (suffix)
Returns the current active suffix (*note pseudo macro::).

This Scheme function takes no arguments.

`tpl-file' - get the template file name
---------------------------------------

Usage:  (tpl-file)
Returns the name of the current template file.

This Scheme function takes no arguments.

`tpl-file-line' - get the template file and line number
-------------------------------------------------------

Usage:  (tpl-file-line [ msg-fmt ])
Returns the file and line number of the current template macro using
either the default format, "from %s line %d", or else the format you
supply.  For example, if you want to insert a "C" language file-line
directive, you would supply the format "# %2$d %1$s".

Arguments:
msg-fmt - Optional - formatting for line message

`make-header-guard' - make self-inclusion guard
-----------------------------------------------

Emit a `#ifndef'/`#define' sequence based upon the output file name
and the provided prefix.  It will also define a scheme variables
named, `header-file' and `header-guard'.  The `#define' name is
composed as follows:

  1. The first element is the string argument and a separating
     underscore.

  2. That is followed by the name of the header file with illegal
     characters mapped to underscores.

  3. The end of the name is always, "`_GUARD'".

  4. Finally, the entire string is mapped to upper case.

The final `#define' name is stored in an SCM symbol named
`header-guard'.  Consequently, the concluding `#endif' for the file
should read something like:

     #endif /* [+ (. header-guard) +] */

The name of the header file (the current output file) is also stored
in an SCM symbol, `header-file'.  Therefore, if you are also
generating a C file that uses the previously generated header file,
you can put this into that generated file:

     #include "[+ (. header-file) +]"

Obviously, if you are going to produce more than one header file from
a particular template, you will need to be careful how these SCM
symbols get handled.

Arguments:
prefix - first segment of `#define' name

`autogen-version' - autogen version number
------------------------------------------

This is a symbol defining the current AutoGen version number string.
It was first defined in AutoGen-5.2.14.  It is currently "5.5.3".

Common Scheme Functions
=======================

This section describes a number of general purpose functions that make
the kind of string processing that AutoGen does a little easier.
Unlike the AutoGen specific functions (*note AutoGen Functions::),
these functions are available for direct use during definition load
time.

`bsd' - BSD Public License
--------------------------

Usage:  (bsd prog_name owner prefix)
Emit a string that contains the Free BSD Public License.  It takes
three arguments: `prefix' contains the string to start each output
line.  `owner' contains the copyright owner.  `prog_name' contains
the name of the program the copyright is about.

Arguments:
prog_name - name of the program under the BSD
owner - Grantor of the BSD License
prefix - String for starting each output line

`c-string' - emit string for ANSI C
-----------------------------------

Usage:  (c-string string)
Reform a string so that, when printed, the C compiler will be able to
compile the data and construct a string that contains exactly what the
current string contains.  Many non-printing characters are replaced
with escape sequences.  Newlines are replaced with a backslash, an
`n', a closing quote, a newline, seven spaces and another re-opening
quote.  The compiler will implicitly concatenate them.  The reader
will see line breaks.

A K&R compiler will choke.  Use `kr-string' for that compiler.

Arguments:
string - string to reformat

`error-source-line' - display of file & line
--------------------------------------------

Usage:  (error-source-line)
This function is only invoked just before Guile displays an error
message.  It displays the file name and line number that triggered
the evaluation error.  You should not need to invoke this routine
directly.  Guile will do it automatically.

This Scheme function takes no arguments.

`extract' - extract text from another file
------------------------------------------

Usage:  (extract file-name marker-fmt [ caveat ] [ default ])
This function is used to help construct output files that may contain
text that is carried from one version of the output to the next.

The first two arguments are required, the second are optional:

   * The `file-name' argument is used to name the file that contains
     the demarcated text.

   * The `marker-fmt' is a formatting string that is used to construct
     the starting and ending demarcation strings.  The sprintf
     function is given the `marker-fmt' with two arguments.  The
     first is either "START" or "END".  The second is either "DO NOT
     CHANGE THIS COMMENT" or the optional `caveat' argument.

   * `caveat' is presumed to be absent if it is the empty string
     (`""').  If absent, "DO NOT CHANGE THIS COMMENT" is used as the
     second string argument to the `marker-fmt'.

   * When a `default' argument is supplied and no pre-existing text
     is found, then this text will be inserted between the START and
     END markers.

The resulting strings are presumed to be unique within the subject
file.  As a simplified example:

     [+ (extract "fname" "// %s - SOMETHING - %s" ""
     "example default") +]

will result in the following text being inserted into the output:

     // START - SOMETHING - DO NOT CHANGE THIS COMMENT
     example default
     // END   - SOMETHING - DO NOT CHANGE THIS COMMENT

The "`example default'" string can then be carried forward to the
next generation of the output, *provided* the output is not named
"`fname'" and the old output is renamed to "`fname'" before
AutoGen-eration begins.

*NOTE:*
     You can set aside previously generated source files inside the
     pseudo macro with a Guile/scheme function, extract the text you
     want to keep with this extract function.  Just remember you
     should delete it at the end, too.  Here is an example from my
     Finite State Machine generator:

     [+ AutoGen5 Template  -*- Mode: text -*-
     h=%s-fsm.h   c=%s-fsm.c
     (shellf
     "[ -f %1$s-fsm.h ] && mv -f %1$s-fsm.h .fsm.head
     [ -f %1$s-fsm.c ] && mv -f %1$s-fsm.c .fsm.code" (base-name)) +]

This code will move the two previously produced output files to files
named ".fsm.head" and ".fsm.code".  At the end of the 'c' output
processing, I delete them.

Arguments:
file-name - name of file with text
marker-fmt - format for marker text
caveat - Optional - warn about changing marker
default - Optional - default initial text

`format-arg-count' - count the args to a format
-----------------------------------------------

Usage:  (format-arg-count format)
Sometimes, it is useful to simply be able to figure out how many
arguments are required by a format string.  For example, if you are
extracting a format string for the purpose of generating a macro to
invoke a printf-like function, you can run the formatting string
through this function to determine how many arguments to provide for
in the macro. e.g. for this extraction text:

      /*=fumble bumble
       * fmt: 'stumble %s: %d\n'
      =*/

You may wish to generate a macro:

      #define BUMBLE(a1,a2) printf_like(something,(a1),(a2))

You can do this by knowing that the format needs two arguments.

Arguments:
format - formatting string

`fprintf' - format to a file
----------------------------

Usage:  (fprintf port format [ format-arg ... ])
Format a string using arguments from the alist.  Write to a specified
port.  The result will NOT appear in your output.  Use this to print
information messages to a template user.

Arguments:
port - Guile-scheme output port
format - formatting string
format-arg - Optional - list of arguments to formatting string

`gperf' - perform a perfect hash function
-----------------------------------------

Usage:  (gperf name str)
Perform the perfect hash on the input string.  This is only useful if
you have previously created a gperf program with the `make-gperf'
function *Note SCM make-gperf::.  The `name' you supply here must
match the name used to create the program and the string to hash must
be one of the strings supplied in the `make-gperf' string list.  The
result will be a perfect hash index.

See the documentation for `gperf(1GNU)' for more details.

Arguments:
name - name of hash list
str - string to hash

`gpl' - GNU General Public License
----------------------------------

Usage:  (gpl prog-name prefix)
Emit a string that contains the GNU General Public License.  It takes
two arguments: `prefix' contains the string to start each output
line, and `prog_name' contains the name of the program the copyright
is about.

Arguments:
prog-name - name of the program under the GPL
prefix - String for starting each output line

`hide-email' - convert eaddr to javascript
------------------------------------------

Usage:  (hide-email display eaddr)
Hides an email address as a java scriptlett.  The 'mailto:' tag and
the email address are coded bytes rather than plain text.  They are
also broken up.

Arguments:
display - display text
eaddr - email address

`in?' - test for string in list
-------------------------------

Usage:  (in? test-string string-list ...)
Return SCM_BOOL_T if the first argument string is found in one of the
entries in the second (list-of-strings) argument.

Arguments:
test-string - string to look for
string-list - list of strings to check

`join' - join string list with separator
----------------------------------------

Usage:  (join separator list ...)
With the first argument as the separator string, joins together an
a-list of strings into one long string.  The list may contain nested
lists, partly because you cannot always control that.

Arguments:
separator - string to insert between entries
list - list of strings to join

`kr-string' - emit string for K&R C
-----------------------------------

Usage:  (kr-string string)
Reform a string so that, when printed, a K&R C compiler will be able
to compile the data and construct a string that contains exactly what
the current string contains.  Many non-printing characters are
replaced with escape sequences.  New-lines are replaced with a
backslash-n-backslash and newline sequence,

Arguments:
string - string to reformat

`lgpl' - GNU Library General Public License
-------------------------------------------

Usage:  (lgpl prog_name owner prefix)
Emit a string that contains the GNU Library General Public License.
It takes three arguments:  `prefix' contains the string to start each
output line.  `owner' contains the copyright owner.  `prog_name'
contains the name of the program the copyright is about.

Arguments:
prog_name - name of the program under the LGPL
owner - Grantor of the LGPL
prefix - String for starting each output line

`license' - an arbitrary license
--------------------------------

Usage:  (license lic_name prog_name owner prefix)
Emit a string that contains the named license.  The license text is
read from a file named, `lic_name'.lic, searching the standard
directories.  The file contents are used as a format argument to
`printf'(3), with `prog_name' and `owner' as the two string
formatting arguments.  Each output line is automatically prefixed
with the string `prefix'.

Arguments:
lic_name - file name of the license
prog_name - name of the licensed program or library
owner - Grantor of the License
prefix - String for starting each output line

`make-gperf' - build a perfect hash function program
----------------------------------------------------

Usage:  (make-gperf name strings ...)
Build a program to perform perfect hashes of a known list of input
strings.  This function produces no output, but prepares a program
named, `gperf_<name>' for use by the gperf function *Note SCM gperf::.

This program will be obliterated within a few seconds after AutoGen
exits.

Arguments:
name - name of hash list
strings - list of strings to hash

`makefile-script' - create makefile script
------------------------------------------

Usage:  (makefile-script text)
This function will take ordinary shell script text and reformat it so
that it will work properly inside of a makefile shell script.  Not
every shell construct can be supported; the intent is to have most
ordinary scripts work without much, if any, alteration.

The following transformations are performed on the source text:

  1. Trailing whitespace on each line is stripped.

  2. Except for the last line, the string, " ; \\" is appended to the
     end of every line that does not end with a backslash, semi-colon,
     conjunction operator or pipe.  Note that this will mutilate
     multi-line quoted strings, but `make' renders it impossible to
     use multi-line constructs anyway.

  3. If the line ends with a backslash, it is left alone.

  4. If the line ends with one of the excepted operators, then a
     space and backslash is added.

  5. The dollar sign character is doubled, unless it immediately
     precedes an opening parenthesis or the single character make
     macros '*', '<', '@', '?' or '%'.  Other single character make
     macros that do not have enclosing parentheses will fail.  For
     shell usage of the "$@", "$?" and "$*" macros, you must enclose
     them with curly braces, e.g., "${?}".  The ksh construct
     `$(<command>)' will not work.  Though some `make's accept
     `${var}' constructs, this function will assume it is for shell
     interpretation and double the dollar character.  You must use
     `$(var)' for all `make' substitutions.

  6. Double dollar signs are replaced by four before the next
     character is examined.

  7. Every line is prefixed with a tab, unless the first line already
     starts with a tab.

  8. The newline character on the last line, if present, is
     suppressed.

  9. Blank lines are stripped.

This function is intended to be used approximately as follows:

     $(TARGET) : $(DEPENDENCIES)
     <+ (out-push-new) +>
     ....mostly arbitrary shell script text....
     <+ (makefile-script (out-pop #t)) +>

Arguments:
text - the text of the script

`max' - maximum value in list
-----------------------------

Usage:  (max list ...)
Return the maximum value in the list

Arguments:
list - list of values.  Strings are converted to numbers

`min' - minimum value in list
-----------------------------

Usage:  (min list ...)
Return the minimum value in the list

Arguments:
list - list of values.  Strings are converted to numbers

`prefix' - prefix lines with a string
-------------------------------------

Usage:  (prefix prefix text)
Prefix every line in the second string with the first string.

For example, if the first string is "# " and the second contains:
     two
     lines

The result string will contain:
     # two
     # lines

Arguments:
prefix - string to insert at start of each line
text - multi-line block of text

`printf' - format to stdout
---------------------------

Usage:  (printf format [ format-arg ... ])
Format a string using arguments from the alist.  Write to the
standard out port.  The result will NOT appear in your output.  Use
this to print information messages to a template user.  Use "(sprintf
...)" to add text to your document.

Arguments:
format - formatting string
format-arg - Optional - list of arguments to formatting string

`raw-shell-str' - single quote shell string
-------------------------------------------

Usage:  (raw-shell-str string)
Convert the text of the string into a singly quoted string that a
normal shell will process into the original string.  (It will not do
macro expansion later, either.)  Contained single quotes become
tripled, with the middle quote escaped with a backslash.  Normal
shells will reconstitute the original string.

*NOTE*:  some shells will not correctly handle unusual non-printing
characters.  This routine works for most reasonably conventional
ASCII strings.

Arguments:
string - string to transform

`shell' - invoke a shell script
-------------------------------

Usage:  (shell command)
Generate a string by writing the value to a server shell and reading
the output back in.  The template programmer is responsible for
ensuring that it completes within 10 seconds.  If it does not, the
server will be killed, the output tossed and a new server started.

Arguments:
command - shell command - the result value is stdout

`shell-str' - double quote shell string
---------------------------------------

Usage:  (shell-str string)
Convert the text of the string into a double quoted string that a
normal shell will process into the original string, almost.  It will
add the escape character `\\' before two special characters to
accomplish this: the backslash `\\' and double quote `"'.

*NOTE*: some shells will not correctly handle unusual non-printing
characters.  This routine works for most reasonably conventional
ASCII strings.

*WARNING*:
This function omits the extra backslash in front of a backslash,
however, if it is followed by either a backquote or a dollar sign.
It must do this because otherwise it would be impossible to protect
the dollar sign or backquote from shell evaluation.  Consequently, it
is not possible to render the strings "\\$" or "\\`".  The lesser of
two evils.

All others characters are copied directly into the output.

The `sub-shell-str' variation of this routine behaves identically,
except that the extra backslash is omitted in front of `"' instead of
``'.  You have to think about it.  I'm open to suggestions.

Meanwhile, the best way to document is with a detailed output example.
If the backslashes make it through the text processing correctly,
below you will see what happens with three example strings.  The first
example string contains a list of quoted `foo's, the second is the
same with a single backslash before the quote characters and the last
is with two backslash escapes.  Below each is the result of the
`raw-shell-str', `shell-str' and `sub-shell-str' functions.

     foo[0]           'foo' "foo" `foo` $foo
     raw-shell-str -> ''\''foo'\'' "foo" `foo` $foo'
     shell-str     -> "'foo' \"foo\" `foo` $foo"
     sub-shell-str -> `'foo' "foo" \`foo\` $foo`
     
     foo[1]           \'bar\' \"bar\" \`bar\` \$bar
     raw-shell-str -> '\'\''bar\'\'' \"bar\" \`bar\` \$bar'
     shell-str     -> "\\'bar\\' \\\"bar\\\" \`bar\` \$bar"
     sub-shell-str -> `\\'bar\\' \"bar\" \\\`bar\\\` \$bar`
     
     foo[2]           \\'BAZ\\' \\"BAZ\\" \\`BAZ\\` \\$BAZ
     raw-shell-str -> '\\'\''BAZ\\'\'' \\"BAZ\\" \\`BAZ\\` \\$BAZ'
     shell-str     -> "\\\\'BAZ\\\\' \\\\\"BAZ\\\\\" \\\`BAZ\\\` \\\$BAZ"
     sub-shell-str -> `\\\\'BAZ\\\\' \\\"BAZ\\\" \\\\\`BAZ\\\\\` \\\$BAZ`

There should be four, three, five and three backslashes for the four
examples on the last line, respectively.  The next to last line should
have four, five, three and three backslashes.  If this was not
accurately reproduced, take a look at the agen5/test/shell.test test.
Notice the backslashes in front of the dollar signs.  It goes from
zero to one to three for the "cooked" string examples.

Arguments:
string - string to transform

`shellf' - format a string, run shell
-------------------------------------

Usage:  (shellf format [ format-arg ... ])
Format a string using arguments from the alist, then send the result
to the shell for interpretation.

Arguments:
format - formatting string
format-arg - Optional - list of arguments to formatting string

`sprintf' - format a string
---------------------------

Usage:  (sprintf format [ format-arg ... ])
Format a string using arguments from the alist.

Arguments:
format - formatting string
format-arg - Optional - list of arguments to formatting string

`string-capitalize' - capitalize a new string
---------------------------------------------

Usage:  (string-capitalize str)
Create a new SCM string containing the same text as the original,
only all the first letter of each word is upper cased and all other
letters are made lower case.

Arguments:
str - input string

`string-capitalize!' - capitalize a string
------------------------------------------

Usage:  (string-capitalize! str)
capitalize all the words in an SCM string.

Arguments:
str - input/output string

`string-contains-eqv?' - caseless substring
-------------------------------------------

Usage:  (*=* text match)
string-contains-eqv?:  Test to see if a string contains an equivalent
string.  `equivalent' means the strings match, but without regard to
character case and certain characters are considered `equivalent'.
Viz., '-', '_' and '^' are equivalent.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-contains?' - substring match
------------------------------------

Usage:  (*==* text match)
string-contains?:  Test to see if a string contains a substring.
"strstr(3)" will find an address.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-downcase' - lower case a new string
-------------------------------------------

Usage:  (string-downcase str)
Create a new SCM string containing the same text as the original,
only all the upper case letters are changed to lower case.

Arguments:
str - input string

`string-downcase!' - make a string be lower case
------------------------------------------------

Usage:  (string-downcase! str)
Change to lower case all the characters in an SCM string.

Arguments:
str - input/output string

`string-end-eqv-match?' - caseless regex ending
-----------------------------------------------

Usage:  (*~ text match)
string-end-eqv-match?:  Test to see if a string ends with a pattern.
Case is not significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-end-match?' - regex match end
-------------------------------------

Usage:  (*~~ text match)
string-end-match?:  Test to see if a string ends with a pattern.
Case is significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-ends-eqv?' - caseless string ending
-------------------------------------------

Usage:  (*= text match)
string-ends-eqv?:  Test to see if a string ends with an equivalent
string.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-ends-with?' - string ending
-----------------------------------

Usage:  (*== text match)
string-ends-with?:  Test to see if a string ends with a substring.
strcmp(3) returns zero for comparing the string ends.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-equals?' - string matching
----------------------------------

Usage:  (== text match)
string-equals?:  Test to see if two strings exactly match.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-eqv-match?' - caseless regex match
------------------------------------------

Usage:  (~ text match)
string-eqv-match?:  Test to see if a string fully matches a pattern.
Case is not significant, but any character equivalences must be
expressed in your regular expression.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-eqv?' - caseless string match
-------------------------------------

Usage:  (= text match)
string-eqv?:  Test to see if two strings are equivalent.
`equivalent' means the strings match, but without regard to character
case and certain characters are considered `equivalent'.  Viz., '-',
'_' and '^' are equivalent.  If the arguments are not strings, then
the result of the numeric comparison is returned.

This is an overloaded operation.  If the arguments are not both
strings, then the query is passed through to `scm_num_eq_p()'.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-has-eqv-match?' - caseless regex contains
-------------------------------------------------

Usage:  (*~* text match)
string-has-eqv-match?:  Test to see if a string contains a pattern.
Case is not significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-has-match?' - contained regex match
-------------------------------------------

Usage:  (*~~* text match)
string-has-match?:  Test to see if a string contains a pattern.  Case
is significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-match?' - regex match
-----------------------------

Usage:  (~~ text match)
string-match?:  Test to see if a string fully matches a pattern.
Case is significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-start-eqv-match?' - caseless regex start
------------------------------------------------

Usage:  (~* text match)
string-start-eqv-match?:  Test to see if a string starts with a
pattern.  Case is not significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-start-match?' - regex match start
-----------------------------------------

Usage:  (~~* text match)
string-start-match?:  Test to see if a string starts with a pattern.
Case is significant.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-starts-eqv?' - caseless string start
--------------------------------------------

Usage:  (=* text match)
string-starts-eqv?:  Test to see if a string starts with an
equivalent string.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-starts-with?' - string starting
---------------------------------------

Usage:  (==* text match)
string-starts-with?:  Test to see if a string starts with a substring.

Arguments:
text - text to test for pattern
match - pattern/substring to search for

`string-substitute' - multiple global replacements
--------------------------------------------------

Usage:  (string-substitute source match repl)
`match' and  `repl' may be either a single string or a list of
strings.  Either way, they must have the same structure and number of
elements.  For example, to replace all less than and all greater than
characters, do something like this:

     (string-substitute source
     ("&"     "<"    ">")
     ("&amp;" "&lt;" "&gt;"))

Arguments:
source - string to transform
match - substring or substring list to be replaced
repl - replacement strings or substrings

`string->c-name!' - map non-name chars to underscore
----------------------------------------------------

Usage:  (string->c-name! str)
Change all the graphic characters that are invalid in a C name token
into underscores.  Whitespace characters are ignored.  Any other
character type (i.e. non-graphic and non-white) will cause a failure.

Arguments:
str - input/output string

`string-tr' - convert characters with new result
------------------------------------------------

Usage:  (string-tr source match translation)
This is identical to `string-tr!', except that it does not over-write
the previous value.

Arguments:
source - string to transform
match - characters to be converted
translation - conversion list

`string-tr!' - convert characters
---------------------------------

Usage:  (string-tr! source match translation)
This is the same as the `tr(1)' program, except the string to
transform is the first argument.  The second and third arguments are
used to construct mapping arrays for the transformation of the first
argument.

It is too bad this little program has so many different and
incompatible implementations!

Arguments:
source - string to transform
match - characters to be converted
translation - conversion list

`string-upcase' - upper case a new string
-----------------------------------------

Usage:  (string-upcase str)
Create a new SCM string containing the same text as the original,
only all the lower case letters are changed to upper case.

Arguments:
str - input string

`string-upcase!' - make a string be upper case
----------------------------------------------

Usage:  (string-upcase! str)
Change to upper case all the characters in an SCM string.

Arguments:
str - input/output string

`sub-shell-str' - back quoted (sub-)shell string
------------------------------------------------

Usage:  (sub-shell-str string)
This function is substantially identical to `shell-str', except that
the quoting character is ``' and the "leave the escape alone"
character is `"'.

Arguments:
string - string to transform

`sum' - sum of values in list
-----------------------------

Usage:  (sum list ...)
Compute the sum of the list of expressions.

Arguments:
list - list of values.  Strings are converted to numbers

`html-escape-encode' - escape special chars
-------------------------------------------

Usage:  (html-escape-encode str)
Substitute escape sequences for characters that are special to
HTML/XML.  It will replace "`&'", "`<'" and "`>'" with the strings,
"`&amp;'", "`&lt;'", and "`&gt;'", respectively.

Arguments:
str - string to transform

AutoGen Native Macros
=====================

This section describes the various AutoGen natively defined macros.
Unlike the Scheme functions, some of these macros are "block macros"
with a scope that extends through a terminating macro.  Block macros
must not overlap.  That is to say, a block macro started within the
scope of an encompassing block macro must have its matching end macro
appear before the encompassing block macro is either ended or
subdivided.

The block macros are these:

`CASE'
     This macro has scope through the `ESAC' macro.  The scope is
     subdivided by `SELECT' macros.  You must have at least one
     `SELECT' macro.

`DEFINE'
     This macro has scope through the `ENDDEF' macro.  The defined
     user macro can never be a block macro.

`FOR'
     This macro has scope through the `ENDFOR' macro.

`IF'
     This macro has scope through the `ENDIF' macro.  The scope may
     be subdivided by `ELIF' and `ELSE' macros.  Obviously, there may
     be only one `ELSE' macro and it must be the last of these
     subdivisions.

`INCLUDE'
     This macro has the scope of the included file.  It is a block
     macro in the sense that the included file must not contain any
     incomplete block macros.

`WHILE'
     This macro has scope through the `ENDWHILE' macro.


AutoGen Macro Syntax
--------------------

The general syntax is:

     [ { <native-macro-name> | <user-defined-name> } ] [ <arg> ... ]

The syntax for `<arg>' depends on the particular macro, but is
generally a full expression (*note expression syntax::).  Here are
the exceptions to that general rule:

  1. `INVOKE' macros, implicit or explicit, must be followed by a
     list of name/string value pairs.  The string values are simple
     expressions, as described above.

     That is, the `INVOKE' syntax is either:
          <user-macro-name> [ <name> [ = <expression> ] ... ]

     or
          INVOKE <name-expression> [ <name> [ = <expression> ] ... ]

  2. AutoGen FOR macros must be in one of two forms:

          FOR <name> [ <separator-string> ]

     or
          FOR <name> (...Scheme expression list)

     where `<name>' must be a simple name and the Scheme expression
     list is expected to contain one or more of the `for-from',
     `for-to', `for-by', and `for-sep' functions.  (*Note FOR::, and
     *Note AutoGen Functions::)

  3. AutoGen `DEFINE' macros must be followed by a simple name.
     Anything after that is ignored.  *Note DEFINE::.

  4. The AutoGen `COMMENT', `ELSE', `ESAC' and the `END*' macros take
     no arguments and ignore everything after the macro name (e.g.
     see *Note COMMENT::)

CASE - Select one of several template blocks
--------------------------------------------

The arguments are evaluated and converted to a string, if necessary.
(*note EXPR::)  The scope of the macro is up to the matching ESAC
function.  Within the scope of a CASE, this string is matched against
case selection macros.  There are sixteen match macros that are
derived from four different ways the test may be performed, plus an
"always true" match.  The code for each selection expression is
formed as follows:

  1. Must the match start matching from the beginning of the string?
     If not, then the match macro code starts with an asterisk (`*').

  2. Must the match finish matching at the end of the string?  If
     not, then the match macro code ends with an asterisk (`*').

  3. Is the match a pattern match or a string comparison?  If a
     comparison, use an equal sign (`=').  If a pattern match, use a
     tilde (`~').

  4. Is the match case sensitive?  If alphabetic case is important,
     double the tilde or equal sign.

  5. Do you need a default match when none of the others match?  Use
     a single asterisk (`*').

For example:

     [+ CASE <full-expression> +]
     [+ ~~*  "[Tt]est" +]reg exp must match at start, not at end
     [+ ==   "TeSt"    +]a full-string, case sensitive compare
     [+ =    "TEST"    +]a full-string, case insensitive compare
     [+ *              +]always match - no testing
     [+ ESAC +]

`<full-expression>' (*note expression syntax::) may be any expression,
including the use of apply-codes and value-names.  If the expression
yields a number, it is converted to a decimal string.

These case selection codes have also been implemented as Scheme
expression functions using the same codes (*note Common Functions::).

COMMENT - A block of comment to be ignored
------------------------------------------

This function can be specified by the user, but there will never be a
situation where it will be invoked at emit time.  The macro is
actually removed from the internal representation.

If the native macro name code is `#', then the entire macro function
is treated as a comment and ignored.

DEFINE - Define a user AutoGen macro
------------------------------------

This function will define a new macro.  You must provide a name for
the macro.  You do not specify any arguments, though the invocation
may specify a set of name/value pairs that are to be active during the
processing of the macro.

     [+ define foo +]
     ... macro body with macro functions ...
     [+ enddef +]
     ... [+ foo bar='raw text' baz=<<text expression>> +]

Once the macro has been defined, this new macro can be invoked by
specifying the macro name as the first token after the start macro
marker.  Alternatively, you may make the invocation explicitly invoke
a defined macro by specifying `INVOKE' in the macro invocation.  If
you do that, the macro name can be computed with an expression that
gets evaluated every time the INVOKE macro is encountered.  *Note
INVOKE::.

Any remaining text in the macro invocation will be used to create new
name/value pairs that only persist for the duration of the processing
of the macro.  The expressions are evaluated the same way basic
expressions are evaluated.  *Note expression syntax::.

The resulting definitions are handled much like regular definitions,
except:

  1. The values may not be compound.  That is, they may not contain
     nested name/value pairs.

  2. The bindings go away when the macro is complete.

  3. The name/value pairs are separated by whitespace instead of
     semi-colons.

  4. Sequences of strings are not concatenated.

ELIF - Alternate Conditional Template Block
-------------------------------------------

This macro must only appear after an `IF' function, and before any
associated `ELSE' or `ENDIF' functions.  It denotes the start of an
alternate template block for the `IF' function.  Its expression
argument is evaluated as are the arguments to `IF'.  For a complete
description *Note IF::.

ELSE - Alternate Template Block
-------------------------------

This macro must only appear after an `IF' function, and before the
associated `ENDIF' function.  It denotes the start of an alternate
template block for the `IF' function.  For a complete description
*Note IF::.

ENDDEF - Ends a macro definition.
---------------------------------

This macro ends the `DEFINE' function template block.  For a complete
description *Note DEFINE::.

ENDFOR - Terminates the `FOR' function template block
-----------------------------------------------------

This macro ends the `FOR' function template block.  For a complete
description *Note FOR::.

ENDIF - Terminate the `IF' Template Block
-----------------------------------------

This macro ends the `IF' function template block.  For a complete
description *Note IF::.

ENDWHILE - Terminate the `WHILE' Template Block
-----------------------------------------------

This macro ends the `WHILE' function template block.  For a complete
description *Note WHILE::.

ESAC - Terminate the `CASE' Template Block
------------------------------------------

This macro ends the `CASE' function template block.  For a complete
description, *Note CASE::.

EXPR - Evaluate and emit an Expression
--------------------------------------

This macro does not have a name to cause it to be invoked explicitly,
though if a macro starts with one of the apply codes or one of the
simple expression markers, then an expression macro is inferred.  The
result of the expression evaluation (*note expression syntax::) is
written to the current output.

FOR - Emit a template block multiple times
------------------------------------------

This macro has a slight variation on the standard syntax:
     FOR <value-name> [ <separator-string> ]
or
     FOR <value-name> (...Scheme expression list
or
     FOR <value-name> IN "quoted string" unquoted-string ...

Other than for the last form, the first macro argument must be the
name of an AutoGen value.  If there is no value associated with the
name, the `FOR' template block is skipped entirely.  The scope of the
`FOR' macro extends to the corresponding `ENDFOR' macro.  The last
form will create an array of string values named `<value-name>' that
only exists within the context of this `FOR' loop.  With this form,
in order to use a `separator-string', you must code it into the end
of the template block using the `(last-for?)' predicate function
(*note SCM last-for?::).

If there are any arguments after the `value-name', the initial
characters are used to determine the form.  If the first character is
either a semi-colon (`;') or an opening parenthesis (`('), then it is
presumed to be a Scheme expression containing the FOR macro specific
functions `for-from', `for-by', `for-to', and/or `for-sep'.  *Note
AutoGen Functions::.  If it consists of an '`i'' an '`n'' and
separated by white space from more text, then the `FOR x IN' form is
processed.  Otherwise, the remaining text is presumed to be a string
for inserting between each iteration of the loop.  This string will
be emitted one time less than the number of iterations of the loop.
That is, it is emitted after each loop, excepting for the last
iteration.

If the from/by/to functions are invoked, they will specify which
copies of the named value are to be processed.  If there is no copy
of the named value associated with a particular index, the `FOR'
template block will be instantiated anyway.  The template must use
methods for detecting missing definitions and emitting default text.
In this fashion, you can insert entries from a sparse or non-zero
based array into a dense, zero based array.

*NB:* the `for-from', `for-to', `for-by' and `for-sep' functions are
disabled outside of the context of the `FOR' macro.  Likewise, the
`first-for', `last-for' and `for-index' functions are disabled
outside of the range of a `FOR' block.

     [+FOR var (for-from 0) (for-to <number>) (for-sep ",") +]
     ... text with `var'ious substitutions ...[+
     ENDFOR var+]

this will repeat the `... text with `var'ious substitutions ...'
<number>+1 times.  Each repetition, except for the last, will have a
comma `,' after it.

     [+FOR var ",\n" +]
     ... text with `var'ious substitutions ...[+
     ENDFOR var +]

This will do the same thing, but only for the index values of `var'
that have actually been defined.

IF - Conditionally Emit a Template Block
----------------------------------------

Conditional block.  Its arguments are evaluated (*note EXPR::) and if
the result is non-zero or a string with one or more bytes, then the
condition is true and the text from that point until a matched
`ELIF', `ELSE' or `ENDIF' is emitted.  `ELIF' introduces a
conditional alternative if the `IF' clause evaluated FALSE and `ELSE'
introduces an unconditional alternative.

     [+IF <full-expression> +]
     emit things that are for the true condition[+
     
     ELIF <full-expression-2> +]
     emit things that are true maybe[+
     
     ELSE "This may be a comment" +]
     emit this if all but else fails[+
     
     ENDIF "This may *also* be a comment" +]

`<full-expression>' may be any expression described in the `EXPR'
expression function, including the use of apply-codes and
value-names.  If the expression yields an empty string, it is
interpreted as false.

INCLUDE - Read in and emit a template block
-------------------------------------------

The entire contents of the named file is inserted at this point.  The
contents of the file are processed for macro expansion.  The
arguments are eval-ed, so you may compute the name of the file to be
included.  The included file must not contain any incomplete function
blocks.  Function blocks are template text beginning with any of the
macro functions `CASE', `DEFINE', `FOR', `IF' and `WHILE'; extending
through their respective terminating macro functions.

INVOKE - Invoke a User Defined Macro
------------------------------------

User defined macros may be invoked explicitly or implicitly.  If you
invoke one implicitly, the macro must begin with the name of the
defined macro.  Consequently, this may *not* be a computed value.  If
you explicitly invoke a user defined macro, the macro begins with the
macro name `INVOKE' followed by a basic expression that must yield a
known user defined macro.  A macro name _must_ be found, or AutoGen
will issue a diagnostic and exit.

Arguments are passed to the invoked macro by name.  The text
following the macro name must consist of a series of names each of
which is followed by an equal sign (`=') and a basic expression that
yields a string.

The string values may contain template macros that are parsed the
first time the macro is processed and evaluated again every time the
macro is evaluated.

SELECT - Selection block for CASE function
------------------------------------------

This macro selects a block of text by matching an expression against
the sample text expression evaluated in the `CASE' macro.  *Note
CASE::.

You do not specify a `SELECT' macro with the word "select".  Instead,
you must use one of the 17 match operators described in the `CASE'
macro description.

UNKNOWN - Either a user macro or a value name.
----------------------------------------------

The macro text has started with a name not known to AutoGen.  If, at
run time, it turns out to be the name of a defined macro, then that
macro is invoked.  If it is not, then it is a conditional expression
that is evaluated only if the name is defined at the time the macro
is invoked.

You may not specify `UNKNOWN' explicitly.

WHILE - Conditionally loop over a Template Block
------------------------------------------------

Conditionally repeated block.  Its arguments are evaluated (*note
EXPR::) and as long as the result is non-zero or a string with one or
more bytes, then the condition is true and the text from that point
until a matched `ENDWHILE' is emitted.

     [+WHILE <full-expression> +]
     emit things that are for the true condition[+
     
     ENDWHILE +]

`<full-expression>' may be any expression described in the `EXPR'
expression function, including the use of apply-codes and
value-names.  If the expression yields an empty string, it is
interpreted as false.

Redirecting Output
==================

AutoGen provides a means for redirecting the template output to
different files.  It is accomplished by providing a set of Scheme
functions named `out-*' (*note AutoGen Functions::).

`out-push (*note SCM out-push-new::)'
     This allows you to logically "push" output files onto a stack.

`out-pop (*note SCM out-pop::)'
     This function closes the current output file and resumes output
     to the next one in the stack.

`out-suspend (*note SCM out-suspend::)'
     This function does not close the current output, but instead
     sets it aside for resumption with

`out-resume (*note SCM out-resume::)'
     This will put a named file descriptor back onto the top of stack
     so that it becomes the current output again.

`out-switch (*note SCM out-switch::)'
     This closes the current output and creates a new file, purging
     any preexisting one.  This is a shortcut for "pop" followed by
     "push", but can also be done at the base level.

`out-move (*note SCM out-move::)'
     Renames the current output file without closing it.

There are also several functions for determining the output status.
*Note AutoGen Functions::.

Augmenting AutoGen Features
***************************

AutoGen was designed to be simple to enhance.  You can do it by
providing shell commands, Guile/Scheme macros or callout functions
that can be invoked as a Guile macro.  Here is how you do these.

Shell Output Commands
=====================

Shell commands are run inside of a server process.  This means that,
unlike `make', context is kept from one command to the next.
Consequently, you can define a shell function in one place inside of
your template and invoke it in another.  You may also store values in
shell variables for later reference.  If you load functions from a
file containing shell functions, they will remain until AutoGen exits.

If your shell script should determine that AutoGen should stop
processing, the recommended method for stopping AutoGen is:
     echo "some error text" >&2
     kill -2 ${AG_pid}

Guile Macros
============

Guile also maintains context from one command to the next.  This means
you may define functions and variables in one place and reference them
elsewhere.  You also may load Guile macro definitions from a Scheme
file by using the `--load-scheme' command line option (*note autogen
load-scheme::).  Beware, however, that the AutoGen specific scheme
functions have not been loaded at this time, so though you may define
functions that reference them, do not invoke the AutoGen functions at
this time.

If your Scheme script should determine that AutoGen should stop
processing, the recommended method for stopping AutoGen is:
     (error "some error text")

Guile Callout Functions
=======================

Callout functions must be registered with Guile to work.  This can be
accomplished either by putting your routines into a shared library
that contains a `void scm_init( void )' routine that registers these
routines, or by building them into AutoGen.

To build them into AutoGen, you must place your routines in the source
directory and name the files `exp*.c'.  You also must have a stylized
comment that `getdefs' can find that conforms to the following:

     /*=gfunc <function-name>
      *
      *  what:    <short one-liner>
      *  general_use:
      *  string:  <invocation-name-string>
      *  exparg:  <name>, <description> [, ['optional'] [, 'list']]
      *  doc:     A long description telling people how to use
      *           this function.
     =*/
     SCM
     ag_scm_<function-name>( SCM arg_name[, ...] )
     { <code> }

`gfunc'
     You must have this exactly thus.

`<function-name>'
     This must follow C syntax for variable names

`<short one-liner>'
     This should be about a half a line long.  It is used as a
     subsection title in this document.

`general_use:'
     You must supply this unless you are an AutoGen maintainer and
     are writing a function that queries or modifies the state of
     AutoGen.

`<invocation-name-string>'
     Normally, the `function-name' string will be transformed into a
     reasonable invocation name.  However, that is not always true.
     If the result does not suit your needs, then supply an alternate
     string.

`exparg:'
     You must supply one for each argument to your function.  All
     optional arguments must be last.  The last of the optional
     arguments may be a list, if you choose.

`doc:'
     Please say something meaningful.

`[, ...]'
     Do not actually specify an ANSI ellipsis here.  You must provide
     for all the arguments you specified with `exparg'.

See the Guile documentation for more details.  More information is
also available in a large comment at the beginning of the
`agen5/snarf.tpl' template file.

AutoGen Macros
==============

There are two kinds  those you define yourself and AutoGen native.
The user-defined macros may be defined in your templates or loaded
with the `--lib-template' option (See *Note DEFINE:: and  *Note
autogen lib-template::).

As for AutoGen native macros, do not add any. It is easy to do, but I
won't like it.  The basic functions needed to accomplish looping over
and selecting blocks of text have proven to be sufficient over a
period of several years.  New text transformations can be easily
added via any of the AutoGen extension methods, as discussed above.

Invoking autogen
****************

AutoGen creates text files from templates using external
definitions.The definitions file (`<def-file>') can be specified with
the `definitions' option or as the command argument, but not both.
Omitting it or specifying `-' will result in reading definitions from
standard input.

The output file names are based on the template, but generally use the
base name of the definition file.  If standard in is read for the
definitions, then `stdin' will be used for that base name.  The
suffixes to the base name are gotten from the template.  However, the
template file may specify the entire output file name.  The generated
files are always created in the current directory.  If you need to
place output in an alternate directory, `cd' to that directory and use
the `-templ_dirs' option to search the original directory.

`loop-limit' is used in debugging to stop runaway expansions.

This chapter was generated by *AutoGen*, the aginfo template and the
option descriptions for the *autogen* program.  It documents the
autogen usage text and option meanings.

This software is released under the GNU General Public License.

autogen usage help (-?)
=======================

This is the automatically generated usage text for autogen:

autogen - The Automated Program Generator - Ver. 5.5.3pre5
USAGE:  autogen [ -<flag> [<val>] | --<name>[{=| }<val>] ]... [ <def-file> ]
  Flg Arg Option-Name    Description
   -L Str templ-dirs     Template search directory list
                                - may appear multiple times
   -T Str override-tpl   Override template file
                                - may not be preset
   -l Str lib-template   Library template file
                                - may appear multiple times
   -b Str base-name      Base name for output file(s)
                                - may not be preset
      Str definitions    Definitions input file
                                - disabled as --no-definitions
                                - enabled by default
                                - may not be preset
   -S Str load-scheme    Scheme code file to load
   -F Str load-functions Load scheme callout library
   -s Str skip-suffix    Omit the file with this suffix
                                - may not be preset
                                - may appear multiple times
   -o opt select-suffix  specify this output suffix
                                - may not be preset
                                - may appear multiple times
      no  source-time    set mod times to latest source
                                - disabled as --no-source-time
      Str equate         characters considered equivalent
      no  writable       Allow output files to be writable
                                - disabled as --not-writable
                                - may not be preset

The following options are often useful while debugging new templates:

  Flg Arg Option-Name    Description
      Num loop-limit     Limit on increment loops
                                  it must lie in one of the ranges:
                                  -1 exactly, or
                                  1 to 16777216
   -t Num timeout        Time limit for servers
                                  it must lie in the range: 0 to 3600
      KWd trace          tracing level of detail
      Str trace-out      tracing output file or filter

These options can be used to control what gets processed
in the definitions files and template files.

  Flg Arg Option-Name    Description
   -D Str define         name to add to definition list
                                - may appear multiple times
   -U Str undefine       definition list removal pattern
                                - an alternate for define

Auto-supported Options:

  Flg Arg Option-Name    Description
   -v opt version        Output version information and exit
   -? no  help           Display usage information and exit
   -! no  more-help      Extended usage information passed thru pager
   -> opt save-opts      Save the option state to an rc file
   -< Str load-opts      Load options from an rc file
                                - disabled as --no-load-opts
                                - may appear multiple times

Options are specified by doubled hyphens and their name
or by a single hyphen and the flag character.

AutoGen creates text files from templates using external definitions.

The following option preset mechanisms are supported:
 - reading file /dev/null
 - reading file ./.autogenrc
 - examining environment variables named AUTOGEN_*

The valid trace option keywords are:
        nothing
        templates
        block-macros
        expressions
        everything

The definitions file (`<def-file>') can be specified with the
`definitions' option or as the command argument, but not both.
Omitting it or specifying `-' will result in reading definitions from
standard input.

The output file names are based on the template, but generally use the
base name of the definition file.  If standard in is read for the
definitions, then `stdin' will be used for that base name.  The
suffixes to the base name are gotten from the template.  However, the
template file may specify the entire output file name.  The generated
files are always created in the current directory.  If you need to
place output in an alternate directory, `cd' to that directory and use
the `--templ_dirs' option to search the original directory.

`loop-limit' is used in debugging to stop runaway expansions.

please send bug reports to:  autogen-bugs@lists.sf.net


templ-dirs option (-L)
======================

This is the "template search directory list" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

Add a directory to the list of directories to search when opening a
template, either as the primary template or an included one.  The
last entry has the highest priority in the search list.  That is to
say, they are searched in reverse order.

override-tpl option (-T)
========================

This is the "override template file" option.

This option has some usage constraints.  It:
  * may not be preset with environment variables or in initialization
    (rc) files.

Definition files specify the standard template that is to be expanded.
This option will override that name and expand a different template.

lib-template option (-l)
========================

This is the "library template file" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

DEFINE macros are saved from this template file for use in processing
the main macro file.  Template text aside from the DEFINE macros is
is ignored.

base-name option (-b)
=====================

This is the "base name for output file(s)" option.

This option has some usage constraints.  It:
  * may not be preset with environment variables or in initialization
    (rc) files.

A template may specify the exact name of the output file.  Normally,
it does not.  Instead, the name is composed of the base name of the
definitions file with suffixes appended.  This option will override
the base name derived from the definitions file name.  This is
required if there is no definitions file and advisable if definitions
are being read from stdin.  If the definitions are being read from
standard in, the base name defaults to `stdin'.

definitions option
==================

This is the "definitions input file" option.

This option has some usage constraints.  It:
  * is enabled by default.

  * may not be preset with environment variables or in initialization
    (rc) files.

Use this argument to specify the input definitions file with a
command line option.  If you do not specify this option, then there
must be a command line argument that specifies the file, even if only
to specify stdin with a hyphen (`-').  Specify, `--no-definitions'
when you wish to process a template without any active AutoGen
definitions.

load-scheme option (-S)
=======================

This is the "scheme code file to load" option.  Use this option to
pre-load Scheme scripts into the Guile interpreter before template
processing begins.  Please note that the AutoGen specific functions
are not loaded until after argument processing.  So, though they may
be specified in lambda functions you define, they may not be invoked
until after option processing is complete.

load-functions option (-F)
==========================

This is the "load scheme callout library" option.  This option is
used to load Guile-scheme callout functions.  The automatically
called initialization routine `scm_init' must be used to register
these routines or data.  This routine can be generated by using the
following command and the `snarf.tpl' template.  Read the
introductory comment in `snarf.tpl' to see what the `getdefs(1AG)'
comment must contain.

First, create a config file for `getdefs', and then invoke `getdefs'
loading that file:
    cat > getdefs.cfg <<EOF
    subblock    exparg=arg_name,arg_desc,arg_optional,arg_list
    defs-to-get gfunc
    template    snarf
    srcfile
    linenum
    assign      group = name_of_some_group
    assign      init  = _init
    EOF
    
    getdefs load=getdefs.cfg <<source-file-list>>

Note, however, that your functions must be named:

    name_of_some_group_scm_<<function_name>>(...)

so you may wish to use a shorter group name.

skip-suffix option (-s)
=======================

This is the "omit the file with this suffix" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

  * may not be preset with environment variables or in initialization
    (rc) files.

Occasionally, it may not be desirable to produce all of the output
files specified in the template.  (For example, only the `.h' header
file, but not the `.c' program text.)  To do this specify
`--skip-suffix=c' on the command line.

select-suffix option (-o)
=========================

This is the "specify this output suffix" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

  * may not be preset with environment variables or in initialization
    (rc) files.

If you wish to override the suffix specifications in the template,
you can use one or more copies of this option.  See the suffix
specification in the *Note pseudo macro:: section of the info doc.

source-time option
==================

This is the "set mod times to latest source" option.  If you stamp
your output files with the `DNE' macro output, then your output files
will always be different, even if the content has not really changed.
If you use this option, then the modification time of the output
files will change only if the input files change.  This will help
reduce unneeded builds.

equate option
=============

This is the "characters considered equivalent" option.  This option
will alter the list of characters considered equivalent.  The default
are the three characters, "_-^".  (The latter is conventional on a
Tandem, and I do a lot of work on the Tandem.)

writable option
===============

This is the "allow output files to be writable" option.

This option has some usage constraints.  It:
  * may not be preset with environment variables or in initialization
    (rc) files.

This option will leave output files writable.Normally, output files
are read-only.

loop-limit option
=================

This is the "limit on increment loops" option.  This option prevents
runaway loops.  For example, if you accidentally specify, "FOR x
(for-from 1) (for-to -1) (for-by 1)", it will take a long time to
finish.  If you do have more than 256 entries in tables, you will
need to specify a new limit with this option.

timeout option (-t)
===================

This is the "time limit for servers" option.

This option has some usage constraints.  It:
  * must be compiled in by defining `SHELL_ENABLED' during the
    compilation.

AutoGen works with a shell server process.  Most normal commands will
complete in less than 10 seconds.  If, however, your commands need
more time than this, use this option.

The valid range is 0 to 3600 seconds (1 hour).  Zero will disable the
server time limit.

trace option
============

This is the "tracing level of detail" option.  This option will cause
AutoGen to display a trace of its template processing.  There are
five levels:

`nothing'
    Does no tracing at all (default)

`templates'
    Traces the invocation of `DEFINE'd macros and `INCLUDE's

`block-macros'
    Traces all block macros.  The above, plus `IF', `FOR', `CASE' and
    `WHILE'.

`expressions'
    Displays the results of expression evaluations

`everything'
    Displays the invocation of every AutoGen macro, even `TEXT'
    macros.

trace-out option
================

This is the "tracing output file or filter" option.  The output
specified may be either a file name, or, if the option argument
begins with the `pipe' operator (`|'), a command that will receive
the tracing output as standard in.  For example, `--traceout='|
less'' will run the trace output through the `less' program.

show-defs option
================

This is the "show the definition tree" option.

This option has some usage constraints.  It:
  * must be compiled in by defining `DEBUG' during the compilation.

  * may not be preset with environment variables or in initialization
    (rc) files.

This will print out the complete definition tree before processing
the template.

show-shell option
=================

This is the "show shell commands" option.

This option has some usage constraints.  It:
  * must be compiled in by defining `DEBUG' during the compilation.

  * may not be preset with environment variables or in initialization
    (rc) files.

This will cause `set -x' to be executed in the shell, with the
resultant output printed to /dev/tty.  This option will have no
effect if `--disable-shell' was specified at configure time.

define option (-D)
==================

This is the "name to add to definition list" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

  * is a member of the define class of options.

The AutoGen define names are used for the following purposes:

 1. Sections of the AutoGen definitions may be enabled or disabled by
    using C-style #ifdef and #ifndef directives.

 2. When defining a value for a name, you may specify the index for a
    particular value.  That index may be a literal value, a define
    option or a value #define-d in the definitions themselves.

 3. The name of a file may be prefixed with `$NAME/'.  The `$NAME'
    part of the name string will be replaced with the define-d value
    for `NAME'.

 4. When AutoGen is finished loading the definitions, the defined
    values are exported to the environment with, `putenv(3)'.  These
    values can then be used in shell scripts with `${NAME}'
    references and in templates with `(getenv "NAME")'.

 5. While processing a template, you may specify an index to retrieve
    a specific value.  That index may also be a define-d value.

undefine option (-U)
====================

This is the "definition list removal pattern" option.

This option has some usage constraints.  It:
  * may appear an unlimited number of times.

  * may not be preset with environment variables or in initialization
    (rc) files.

  * is a member of the define class of options.

Just like 'C', AutoGen uses `#ifdef/#ifndef' preprocessing
directives.  This option will cause the matching names to be removed
from the list of defined values.

Configuring and Installing
**************************

Configuring AutoGen
===================

AutoGen is configured and built using Libtool, Automake and Autoconf.
Consequently, you can install it whereever you wish using the various
`--prefix' options.  To the various configuration options supplied by
these tools, AutoGen adds a few of its own:

`--disable-shell'
    AutoGen is now capable of acting as a CGI forms server, *Note
    AutoGen CGI::.  As such, it will gather its definitions using
    either `GET' or `POST' methods.  All you need to do is have a
    template named `cgi.tpl' handy or specify a different one with a
    command line option.

    However, doing this without disabling the server shell brings
    considerable risk.  If you were to pass user input to a script
    that contained, say, the classic "``rm -rf /`'", you might have a
    problem.  This configuration option will cause shell template
    commands to simply return the command string as the result.  No
    mistakes.  Much safer.  Strongly recommended.  The default is to
    have server shell scripting enabled.

    Disabling the shell will have some build side effects, too.

      * Many of the make check tests will fail, since they assume a
        working server shell.

      * The getdefs and columns programs are not built.  The options
        are distributed as definition files and they cannot be
        expanded with a shell-disabled AutoGen.

      * Similarly, the documentation cannot be regenerated because
        the documentation templates depend on subshell functionality.

`--enable-debug'
    Turning on AutoGen debugging enables very detailed inspection of
    the input definitions and monitoring shell script processing.
    These options are not particularly useful to anyone not directly
    involved in maintaining AutoGen.  If you do choose to enable
    AutoGen debugging, be aware that the usage page was generated
    without these options, so when the build process reaches the
    documentation rebuild, there will be a failure.  `cd' into the
    `agen5' build directory, `make' the `autogen.texi' file and all
    will be well thereafter.

`--with-regex-header'
`--with-header-path'
`--with-regex-lib'
    These three work together to specify how to compile with and link
    to a particular POSIX regular expression library.  The value for
    `--with-regex-header=value' must be the name of the relevant
    header file.  The AutoGen sources will attempt to include that
    source with a `#include <value>' C preprocessing statement.  The
    `path' from the `--with-header-path=path' will be added to
    `CPPFLAGS' as `-Ipath'.  The `lib-specs' from
    `--with-regex-lib=lib-specs' will be added to `LDFLAGS' without
    any adornment.

AutoGen as a CGI server
=======================

AutoGen is now capable of acting as a CGI forms server.  It behaves
as a CGI server if the definitions input is from stdin and the
environment variable `REQUEST_METHOD' is defined and set to either
"GET" or "POST".  If set to anything else, AutoGen will exit with a
failure message.  When set to one of those values, the CGI data will
be converted to AutoGen definitions (*note Definitions File::) and
the template named "`cgi.tpl'" will be processed.

This works by including the name of the real template to process in
the form data and having the "`cgi.tpl'" template include that
template for processing.  I do this for processing the form
<http://autogen.sourceforge.net/conftest.html>.  The "`cgi.tpl'"
looks approximately like this:

    <? AutoGen5 Template ?>
    <?
    IF (not (exist? "template"))                       ?><?
      form-error                                       ?><?
    
    ELIF (=* (get "template") "/")                     ?><?
      form-error                                       ?><?
    
    ELIF (define tpl-file (string-append "cgi-tpl/"
                          (get "template")))
         (access? tpl-file R_OK)