START-INFO-DIR-ENTRY * GNU Utilities: (coreutils). GNU Utilities. * Common options: (coreutils)Common options. Common options. * File permissions: (coreutils)File permissions. Access modes. * Date input formats: (coreutils)Date input formats. * basename: (coreutils)basename invocation. Strip directory and suffix. * cat: (coreutils)cat invocation. Concatenate and write files. * chgrp: (coreutils)chgrp invocation. Change file groups. * chmod: (coreutils)chmod invocation. Change file permissions. * chown: (coreutils)chown invocation. Change file owners/groups. * chroot: (coreutils)chroot invocation. Specify the root directory. * cksum: (coreutils)cksum invocation. Print POSIX CRC checksum. * comm: (coreutils)comm invocation. Compare sorted files by line. * cp: (coreutils)cp invocation. Copy files. * csplit: (coreutils)csplit invocation. Split by context. * cut: (coreutils)cut invocation. Print selected parts of lines. * date: (coreutils)date invocation. Print/set system date and time. * dd: (coreutils)dd invocation. Copy and convert a file. * df: (coreutils)df invocation. Report filesystem disk usage. * dir: (coreutils)dir invocation. List directories briefly. * dircolors: (coreutils)dircolors invocation. Color setup for ls. * dirname: (coreutils)dirname invocation. Strip non-directory suffix. * du: (coreutils)du invocation. Report on disk usage. * echo: (coreutils)echo invocation. Print a line of text. * env: (coreutils)env invocation. Modify the environment. * expand: (coreutils)expand invocation. Convert tabs to spaces. * expr: (coreutils)expr invocation. Evaluate expressions. * factor: (coreutils)factor invocation. Print prime factors * false: (coreutils)false invocation. Do nothing, unsuccessfully. * fmt: (coreutils)fmt invocation. Reformat paragraph text. * fold: (coreutils)fold invocation. Wrap long input lines. * groups: (coreutils)groups invocation. Print group names a user is in. * head: (coreutils)head invocation. Output the first part of files. * hostid: (coreutils)hostid invocation. Print numeric host identifier. * hostname: (coreutils)hostname invocation. Print or set system name. * id: (coreutils)id invocation. Print real/effective uid/gid. * install: (coreutils)install invocation. Copy and change attributes. * join: (coreutils)join invocation. Join lines on a common field. * kill: (coreutils)kill invocation. Send a signal to processes. * link: (coreutils)link invocation. Make hard links between files. * ln: (coreutils)ln invocation. Make links between files. * logname: (coreutils)logname invocation. Print current login name. * ls: (coreutils)ls invocation. List directory contents. * md5sum: (coreutils)md5sum invocation. Print or check message-digests. * mkdir: (coreutils)mkdir invocation. Create directories. * mkfifo: (coreutils)mkfifo invocation. Create FIFOs (named pipes). * mknod: (coreutils)mknod invocation. Create special files. * mv: (coreutils)mv invocation. Rename files. * nice: (coreutils)nice invocation. Modify scheduling priority. * nl: (coreutils)nl invocation. Number lines and write files. * nohup: (coreutils)nohup invocation. Immunize to hangups. * od: (coreutils)od invocation. Dump files in octal, etc. * paste: (coreutils)paste invocation. Merge lines of files. * pathchk: (coreutils)pathchk invocation. Check file name portability. * pr: (coreutils)pr invocation. Paginate or columnate files. * printenv: (coreutils)printenv invocation. Print environment variables. * printf: (coreutils)printf invocation. Format and print data. * ptx: (coreutils)ptx invocation. Produce permuted indexes. * pwd: (coreutils)pwd invocation. Print working directory. * rm: (coreutils)rm invocation. Remove files. * rmdir: (coreutils)rmdir invocation. Remove empty directories. * seq: (coreutils)seq invocation. Print numeric sequences * shred: (coreutils)shred invocation. Remove files more securely. * sleep: (coreutils)sleep invocation. Delay for a specified time. * sort: (coreutils)sort invocation. Sort text files. * split: (coreutils)split invocation. Split into fixed-size pieces. * stat: (coreutils)stat invocation. Report file or filesystem status. * stty: (coreutils)stty invocation. Print/change terminal settings. * su: (coreutils)su invocation. Modify user and group id. * sum: (coreutils)sum invocation. Print traditional checksum. * sync: (coreutils)sync invocation. Synchronize memory and disk. * tac: (coreutils)tac invocation. Reverse files. * tail: (coreutils)tail invocation. Output the last part of files. * tee: (coreutils)tee invocation. Redirect to multiple files. * test: (coreutils)test invocation. File/string tests. * touch: (coreutils)touch invocation. Change file timestamps. * tr: (coreutils)tr invocation. Translate characters. * true: (coreutils)true invocation. Do nothing, successfully. * tsort: (coreutils)tsort invocation. Topological sort. * tty: (coreutils)tty invocation. Print terminal name. * uname: (coreutils)uname invocation. Print system information. * unexpand: (coreutils)unexpand invocation. Convert spaces to tabs. * unlink: (coreutils)unlink invocation. Remove files via unlink syscall. * uniq: (coreutils)uniq invocation. Uniquify files. * users: (coreutils)users invocation. Print current user names. * vdir: (coreutils)vdir invocation. List directories verbosely. * wc: (coreutils)wc invocation. Byte, word, and line counts. * who: (coreutils)who invocation. Print who is logged in. * whoami: (coreutils)whoami invocation. Print effective user id. * yes: (coreutils)yes invocation. Print a string indefinitely. END-INFO-DIR-ENTRY This manual documents version 4.5.4 of the GNU command line utilities. Copyright (C) 1994, 1995, 1996, 2000, 2001, 2002 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". copying GNU Core-utils ************** Introduction ************ This manual is a work in progress: many sections make no attempt to explain basic concepts in a way suitable for novices. Thus, if you are interested, please get involved in improving this manual. The entire GNU community will benefit. The GNU utilities documented here are mostly compatible with the POSIX standard. Please report bugs to . Remember to include the version number, machine architecture, input files, and any other information needed to reproduce the bug: your input, what you expected, what you got, and why it is wrong. Diffs are welcome, but please include a description of the problem as well, since this is sometimes difficult to infer. *Note Bugs: (gcc)Bugs. This manual was originally derived from the Unix man pages in the distributions, which were written by David MacKenzie and updated by Jim Meyering. What you are reading now is the authoritative documentation for these utilities; the man pages are no longer being maintained. The original `fmt' man page was written by Ross Paterson. Franc,ois Pinard did the initial conversion to Texinfo format. Karl Berry did the indexing, some reorganization, and editing of the results. Brian Youmans of the Free Software Foundation office staff combined the manuals for textutils, fileutils, and sh-utils to produce the present omnibus manual. Richard Stallman contributed his usual invaluable insights to the overall process. Common options ************** Certain options are available in all of these programs. Rather than writing identical descriptions for each of the programs, they are described here. (In fact, every GNU program accepts (or should accept) these options.) Normally options and operands can appear in any order, and programs act as if all the options appear before any operands. For example, `sort -r passwd -t :' acts like `sort -r -t : passwd', since `:' is an option-argument of `-t'. However, if the `POSIXLY_CORRECT' environment variable is set, options must appear before operands, unless otherwise specified for a particular command. Some of these programs recognize the `--help' and `--version' options only when one of them is the sole command line argument. `--help' Print a usage message listing all available options, then exit successfully. `--version' Print the version number, then exit successfully. `--' Delimit the option list. Later arguments, if any, are treated as operands even if they begin with `-'. For example, `sort -- -r' reads from the file named `-r'. A single `-' is not really an option, though it looks like one. It stands for standard input, or for standard output if that is clear from the context, and it can be used either as an operand or as an option-argument. For example, `sort -o - -' outputs to standard output and reads from standard input, and is equivalent to plain `sort'. Unless otherwise specified, `-' can appear in any context that requires a file name. Backup options ============== Some GNU programs (at least `cp', `install', `ln', and `mv') optionally make backups of files before writing new versions. These options control the details of these backups. The options are also briefly mentioned in the descriptions of the particular programs. `-b' `--backup[=METHOD]' Make a backup of each file that would otherwise be overwritten or removed. Without this option, the original versions are destroyed. Use METHOD to determine the type of backups to make. When this option is used but METHOD is not specified, then the value of the `VERSION_CONTROL' environment variable is used. And if `VERSION_CONTROL' is not set, the default backup type is `existing'. Note that the short form of this option, `-b' does not accept any argument. Using `-b' is equivalent to using `--backup=existing'. This option corresponds to the Emacs variable `version-control'; the values for METHOD are the same as those used in Emacs. This option also accepts more descriptive names. The valid METHODs are (unique abbreviations are accepted): `none' `off' Never make backups. `numbered' `t' Always make numbered backups. `existing' `nil' Make numbered backups of files that already have them, simple backups of the others. `simple' `never' Always make simple backups. Please note `never' is not to be confused with `none'. `-S SUFFIX' `--suffix=SUFFIX' Append SUFFIX to each backup file made with `-b'. If this option is not specified, the value of the `SIMPLE_BACKUP_SUFFIX' environment variable is used. And if `SIMPLE_BACKUP_SUFFIX' is not set, the default is `~', just as in Emacs. `--version-control=METHOD' This option is obsolete and will be removed in a future release. It has been replaced with `--backup'. Block size ========== Some GNU programs (at least `df', `du', and `ls') display sizes in "blocks". You can adjust the block size and method of display to make sizes easier to read. The block size used for display is independent of any filesystem block size. Fractional block counts are rounded up to the nearest integer. The default block size is chosen by examining the following environment variables in turn; the first one that is set determines the block size. `DF_BLOCK_SIZE' This specifies the default block size for the `df' command. Similarly, `DU_BLOCK_SIZE' specifies the default for `du' and `LS_BLOCK_SIZE' for `ls'. `BLOCK_SIZE' This specifies the default block size for all three commands, if the above command-specific environment variables are not set. `POSIXLY_CORRECT' If neither the `COMMAND_BLOCK_SIZE' nor the `BLOCK_SIZE' variables are set, but this variable is set, the block size defaults to 512. If none of the above environment variables are set, the block size currently defaults to 1024 bytes in most contexts, but this number may change in the future. For `ls' file sizes, the block size defaults to 1 byte. A block size specification can be a positive integer specifying the number of bytes per block, or it can be `human-readable' or `si' to select a human-readable format. Integers may be followed by suffixes that are upward compatible with the SI prefixes (http://www.bipm.fr/enus/3_SI/si-prefixes.html) for decimal multiples and with the IEC 60027-2 prefixes for binary multiples (http://physics.nist.gov/cuu/Units/binary.html). With human-readable formats, output sizes are followed by a size letter such as `M' for megabytes. `BLOCK_SIZE=human-readable' uses powers of 1024; `M' stands for 1,048,576 bytes. `BLOCK_SIZE=si' is similar, but uses powers of 1000 and appends `B'; `MB' stands for 1,000,000 bytes. A block size specification preceded by `'' causes output sizes to be displayed with thousands separators. The `LC_NUMERIC' locale specifies the thousands separator and grouping. For example, in an American English locale, `--block-size="'1kB"' would cause a size of 1234000 bytes to be displayed as `1,234'. In the default C locale, there is no thousands separator so a leading `'' has no effect. An integer block size can be followed by a suffix to specify a multiple of that size. A bare size letter, or one followed by `iB', specifies a multiple using powers of 1024. A size letter followed by `B' specifies powers of 1000 instead. For example, `1M' and `1MiB' are equivalent to `1048576', whereas `1MB' is equivalent to `1000000'. A plain suffix without a preceding integer acts as if `1' were prepended, except that it causes a size indication to be appended to the output. For example, `--block-size="kB"' displays 3000 as `3kB'. The following suffixes are defined. Large sizes like `1Y' may be rejected by your computer due to limitations of its arithmetic. `kB' kilobyte: 10^3 = 1000. `k' `K' `KiB' kibibyte: 2^10 = 1024. `K' is special: the SI prefix is `k' and the IEC 60027-2 prefix is `Ki', but tradition and POSIX use `k' to mean `KiB'. `MB' megabyte: 10^6 = 1,000,000. `M' `MiB' mebibyte: 2^20 = 1,048,576. `GB' gigabyte: 10^9 = 1,000,000,000. `G' `GiB' gibibyte: 2^30 = 1,073,741,824. `TB' terabyte: 10^12 = 1,000,000,000,000. `T' `TiB' tebibyte: 2^40 = 1,099,511,627,776. `PB' petabyte: 10^15 = 1,000,000,000,000,000. `P' `PiB' pebibyte: 2^50 = 1,125,899,906,842,624. `EB' exabyte: 10^18 = 1,000,000,000,000,000,000. `E' `EiB' exbibyte: 2^60 = 1,152,921,504,606,846,976. `ZB' zettabyte: 10^21 = 1,000,000,000,000,000,000,000 `Z' `ZiB' 2^70 = 1,180,591,620,717,411,303,424. (`Zi' is a GNU extension to IEC 60027-2.) `YB' yottabyte: 10^24 = 1,000,000,000,000,000,000,000,000. `Y' `YiB' 2^80 = 1,208,925,819,614,629,174,706,176. (`Yi' is a GNU extension to IEC 60027-2.) Block size defaults can be overridden by an explicit `--block-size=SIZE' option. The `-k' option is equivalent to `--block-size=1K', which is the default unless the `POSIXLY_CORRECT' environment variable is set. The `-h' or `--human-readable' option is equivalent to `--block-size=human-readable'. The `--si' option is equivalent to `--block-size=si'. Target directory ================ Some GNU programs (at least `cp', `install', `ln', and `mv') allow you to specify the target directory via this option: `--target-directory=DIRECTORY' Specify the destination DIRECTORY. The interface for most programs is that after processing options and a finite (possibly zero) number of fixed-position arguments, the remaining argument list is either expected to be empty, or is a list of items (usually files) that will all be handled identically. The `xargs' program is designed to work well with this convention. The commands in the `mv'-family are unusual in that they take a variable number of arguments with a special case at the _end_ (namely, the target directory). This makes it nontrivial to perform some operations, e.g., "move all files from here to ../d/", because `mv * ../d/' might exhaust the argument space, and `ls | xargs ...' doesn't have a clean way to specify an extra final argument for each invocation of the subject command. (It can be done by going through a shell command, but that requires more human labor and brain power than it should.) The `--target-directory' option allows the `cp', `install', `ln', and `mv' programs to be used conveniently with `xargs'. For example, you can move the files from the current directory to a sibling directory, `d' like this: (However, this doesn't move files whose names begin with `.'.) ls |xargs mv --target-directory=../d If you use the GNU `find' program, you can move _all_ files with this command: find . -mindepth 1 -maxdepth 1 \ | xargs mv --target-directory=../d But that will fail if there are no files in the current directory or if any file has a name containing a newline character. The following example removes those limitations and requires both GNU `find' and GNU `xargs': find . -mindepth 1 -maxdepth 1 -print0 \ | xargs --null --no-run-if-empty \ mv --target-directory=../d Trailing slashes ================ Some GNU programs (at least `cp' and `mv') allow you to remove any trailing slashes from each SOURCE argument before operating on it. The `--strip-trailing-slashes' option enables this behavior. This is useful when a SOURCE argument may have a trailing slash and specify a symbolic link to a directory. This scenario is in fact rather common because some shells can automatically append a trailing slash when performing file name completion on such symbolic links. Without this option, `mv', for example, (via the system's rename function) must interpret a trailing slash as a request to dereference the symbolic link and so must rename the indirectly referenced _directory_ and not the symbolic link. Although it may seem surprising that such behavior be the default, it is required by POSIX and is consistent with other parts of that standard. Standards conformance ===================== In a few cases, the GNU utilities' default behavior is incompatible with the POSIX standard. To suppress these incompatibilities, define the `POSIXLY_CORRECT' environment variable. Unless you are checking for POSIX conformance, you probably do not need to define `POSIXLY_CORRECT'. Newer versions of POSIX are occasionally incompatible with older versions. For example, older versions of POSIX required the command `sort +1' to sort based on the second and succeeding fields in each input line, but starting with POSIX 1003.1-2001 the same command is required to sort the file named `+1', and you must instead use the command `sort -k 2' to get the field-based sort. The GNU utilities normally conform to the version of POSIX that is standard for your system. To cause them to conform to a different version of POSIX, define the `_POSIX2_VERSION' environment variable to a value of the form YYYYMM specifying the year and month the standard was adopted. Two values are currently supported for `_POSIX2_VERSION': `199209' stands for POSIX 1003.2-1992, and `200112' stands for POSIX 1003.1-2001. For example, if you are running older software that assumes an older version of POSIX and uses `sort +1', you can work around the compatibility problems by setting `_POSIX2_VERSION=199209' in your environment. Output of entire files ********************** These commands read and write entire files, possibly transforming them in some way. `cat': Concatenate and write files ================================== `cat' copies each FILE (`-' means standard input), or standard input if none are given, to standard output. Synopsis: cat [OPTION] [FILE]... The program accepts the following options. Also see *Note Common options::. `-A' `--show-all' Equivalent to `-vET'. `-B' `--binary' On MS-DOS and MS-Windows only, read and write the files in binary mode. By default, `cat' on MS-DOS/MS-Windows uses binary mode only when standard output is redirected to a file or a pipe; this option overrides that. Binary file I/O is used so that the files retain their format (Unix text as opposed to DOS text and binary), because `cat' is frequently used as a file-copying program. Some options (see below) cause `cat' to read and write files in text mode because in those cases the original file contents aren't important (e.g., when lines are numbered by `cat', or when line endings should be marked). This is so these options work as DOS/Windows users would expect; for example, DOS-style text files have their lines end with the CR-LF pair of characters, which won't be processed as an empty line by `-b' unless the file is read in text mode. `-b' `--number-nonblank' Number all nonblank output lines, starting with 1. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-e' Equivalent to `-vE'. `-E' `--show-ends' Display a `$' after the end of each line. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-n' `--number' Number all output lines, starting with 1. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-s' `--squeeze-blank' Replace multiple adjacent blank lines with a single blank line. On MS-DOS and MS-Windows, this option causes `cat' to read and write files in text mode. `-t' Equivalent to `-vT'. `-T' `--show-tabs' Display TAB characters as `^I'. `-u' Ignored; for Unix compatibility. `-v' `--show-nonprinting' Display control characters except for LFD and TAB using `^' notation and precede characters that have the high bit set with `M-'. On MS-DOS and MS-Windows, this option causes `cat' to read files and standard input in DOS binary mode, so the CR characters at the end of each line are also visible. `tac': Concatenate and write files in reverse ============================================= `tac' copies each FILE (`-' means standard input), or standard input if none are given, to standard output, reversing the records (lines by default) in each separately. Synopsis: tac [OPTION]... [FILE]... "Records" are separated by instances of a string (newline by default). By default, this separator string is attached to the end of the record that it follows in the file. The program accepts the following options. Also see *Note Common options::. `-b' `--before' The separator is attached to the beginning of the record that it precedes in the file. `-r' `--regex' Treat the separator string as a regular expression. Users of `tac' on MS-DOS/MS-Windows should note that, since `tac' reads files in binary mode, each line of a text file might end with a CR/LF pair instead of the Unix-style LF. `-s SEPARATOR' `--separator=SEPARATOR' Use SEPARATOR as the record separator, instead of newline. `nl': Number lines and write files ================================== `nl' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, with line numbers added to some or all of the lines. Synopsis: nl [OPTION]... [FILE]... `nl' decomposes its input into (logical) pages; by default, the line number is reset to 1 at the top of each logical page. `nl' treats all of the input files as a single document; it does not reset line numbers or logical pages between files. A logical page consists of three sections: header, body, and footer. Any of the sections can be empty. Each can be numbered in a different style from the others. The beginnings of the sections of logical pages are indicated in the input file by a line containing exactly one of these delimiter strings: `\:\:\:' start of header; `\:\:' start of body; `\:' start of footer. The two characters from which these strings are made can be changed from `\' and `:' via options (see below), but the pattern and length of each string cannot be changed. A section delimiter is replaced by an empty line on output. Any text that comes before the first section delimiter string in the input file is considered to be part of a body section, so `nl' treats a file that contains no section delimiters as a single body section. The program accepts the following options. Also see *Note Common options::. `-b STYLE' `--body-numbering=STYLE' Select the numbering style for lines in the body section of each logical page. When a line is not numbered, the current line number is not incremented, but the line number separator character is still prepended to the line. The styles are: `a' number all lines, `t' number only nonempty lines (default for body), `n' do not number lines (default for header and footer), `pREGEXP' number only lines that contain a match for REGEXP. `-d CD' `--section-delimiter=CD' Set the section delimiter characters to CD; default is `\:'. If only C is given, the second remains `:'. (Remember to protect `\' or other metacharacters from shell expansion with quotes or extra backslashes.) `-f STYLE' `--footer-numbering=STYLE' Analogous to `--body-numbering'. `-h STYLE' `--header-numbering=STYLE' Analogous to `--body-numbering'. `-i NUMBER' `--page-increment=NUMBER' Increment line numbers by NUMBER (default 1). `-l NUMBER' `--join-blank-lines=NUMBER' Consider NUMBER (default 1) consecutive empty lines to be one logical line for numbering, and only number the last one. Where fewer than NUMBER consecutive empty lines occur, do not number them. An empty line is one that contains no characters, not even spaces or tabs. `-n FORMAT' `--number-format=FORMAT' Select the line numbering format (default is `rn'): `ln' left justified, no leading zeros; `rn' right justified, no leading zeros; `rz' right justified, leading zeros. `-p' `--no-renumber' Do not reset the line number at the start of a logical page. `-s STRING' `--number-separator=STRING' Separate the line number from the text line in the output with STRING (default is the TAB character). `-v NUMBER' `--starting-line-number=NUMBER' Set the initial line number on each logical page to NUMBER (default 1). `-w NUMBER' `--number-width=NUMBER' Use NUMBER characters for line numbers (default 6). `od': Write files in octal or other formats =========================================== `od' writes an unambiguous representation of each FILE (`-' means standard input), or standard input if none are given. Synopses: od [OPTION]... [FILE]... od --traditional [FILE] [[+]OFFSET [[+]LABEL]] Each line of output consists of the offset in the input, followed by groups of data from the file. By default, `od' prints the offset in octal, and each group of file data is two bytes of input printed as a single octal number. The program accepts the following options. Also see *Note Common options::. `-A RADIX' `--address-radix=RADIX' Select the base in which file offsets are printed. RADIX can be one of the following: `d' decimal; `o' octal; `x' hexadecimal; `n' none (do not print offsets). The default is octal. `-j BYTES' `--skip-bytes=BYTES' Skip BYTES input bytes before formatting and writing. If BYTES begins with `0x' or `0X', it is interpreted in hexadecimal; otherwise, if it begins with `0', in octal; otherwise, in decimal. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-N BYTES' `--read-bytes=BYTES' Output at most BYTES bytes of the input. Prefixes and suffixes on `bytes' are interpreted as for the `-j' option. `-s N' `--strings[=N]' Instead of the normal output, output only "string constants": at least N consecutive ASCII graphic characters, followed by a null (zero) byte. If N is omitted with `--strings', the default is 3. On older systems, GNU `od' instead supports an obsolete option `-s[N]', where N also defaults to 3. POSIX 1003.1-2001 (*note Standards conformance::) does not allow `-s' without an argument; use `--strings' instead. `-t TYPE' `--format=TYPE' Select the format in which to output the file data. TYPE is a string of one or more of the below type indicator characters. If you include more than one type indicator character in a single TYPE string, or use this option more than once, `od' writes one copy of each output line using each of the data types that you specified, in the order that you specified. Adding a trailing "z" to any type specification appends a display of the ASCII character representation of the printable characters to the output line generated by the type specification. `a' named character `c' ASCII character or backslash escape, `d' signed decimal `f' floating point `o' octal `u' unsigned decimal `x' hexadecimal The type `a' outputs things like `sp' for space, `nl' for newline, and `nul' for a null (zero) byte. Type `c' outputs ` ', `\n', and `\0', respectively. Except for types `a' and `c', you can specify the number of bytes to use in interpreting each number in the given data type by following the type indicator character with a decimal integer. Alternately, you can specify the size of one of the C compiler's built-in data types by following the type indicator character with one of the following characters. For integers (`d', `o', `u', `x'): `C' char `S' short `I' int `L' long For floating point (`f'): F float D double L long double `-v' `--output-duplicates' Output consecutive lines that are identical. By default, when two or more consecutive output lines would be identical, `od' outputs only the first line, and puts just an asterisk on the following line to indicate the elision. `-w N' `--width[=N]' Dump `n' input bytes per output line. This must be a multiple of the least common multiple of the sizes associated with the specified output types. If this option is not given at all, the default is 16. If N is omitted with `--width', the default is 32. On older systems, GNU `od' instead supports an obsolete option `-w[N]', where N also defaults to 32. POSIX 1003.1-2001 (*note Standards conformance::) does not allow `-w' without an argument; use `--width' instead. The next several options are shorthands for format specifications. GNU `od' accepts any combination of shorthands and format specification options. These options accumulate. `-a' Output as named characters. Equivalent to `-ta'. `-b' Output as octal bytes. Equivalent to `-toC'. `-c' Output as ASCII characters or backslash escapes. Equivalent to `-tc'. `-d' Output as unsigned decimal shorts. Equivalent to `-tu2'. `-f' Output as floats. Equivalent to `-tfF'. `-h' Output as hexadecimal shorts. Equivalent to `-tx2'. `-i' Output as decimal shorts. Equivalent to `-td2'. `-l' Output as decimal longs. Equivalent to `-td4'. `-o' Output as octal shorts. Equivalent to `-to2'. `-x' Output as hexadecimal shorts. Equivalent to `-tx2'. `--traditional' Recognize the non-option arguments that traditional `od' accepted. The following syntax: od --traditional [FILE] [[+]OFFSET[.][b] [[+]LABEL[.][b]]] can be used to specify at most one file and optional arguments specifying an offset and a pseudo-start address, LABEL. By default, OFFSET is interpreted as an octal number specifying how many input bytes to skip before formatting and writing. The optional trailing decimal point forces the interpretation of OFFSET as a decimal number. If no decimal is specified and the offset begins with `0x' or `0X' it is interpreted as a hexadecimal number. If there is a trailing `b', the number of bytes skipped will be OFFSET multiplied by 512. The LABEL argument is interpreted just like OFFSET, but it specifies an initial pseudo-address. The pseudo-addresses are displayed in parentheses following any normal address. Formatting file contents ************************ These commands reformat the contents of files. `fmt': Reformat paragraph text ============================== `fmt' fills and joins lines to produce output lines of (at most) a given number of characters (75 by default). Synopsis: fmt [OPTION]... [FILE]... `fmt' reads from the specified FILE arguments (or standard input if none are given), and writes to standard output. By default, blank lines, spaces between words, and indentation are preserved in the output; successive input lines with different indentation are not joined; tabs are expanded on input and introduced on output. `fmt' prefers breaking lines at the end of a sentence, and tries to avoid line breaks after the first word of a sentence or before the last word of a sentence. A "sentence break" is defined as either the end of a paragraph or a word ending in any of `.?!', followed by two spaces or end of line, ignoring any intervening parentheses or quotes. Like TeX, `fmt' reads entire "paragraphs" before choosing line breaks; the algorithm is a variant of that in "Breaking Paragraphs Into Lines" (Donald E. Knuth and Michael F. Plass, `Software--Practice and Experience', 11 (1981), 1119-1184). The program accepts the following options. Also see *Note Common options::. `-c' `--crown-margin' "Crown margin" mode: preserve the indentation of the first two lines within a paragraph, and align the left margin of each subsequent line with that of the second line. `-t' `--tagged-paragraph' "Tagged paragraph" mode: like crown margin mode, except that if indentation of the first line of a paragraph is the same as the indentation of the second, the first line is treated as a one-line paragraph. `-s' `--split-only' Split lines only. Do not join short lines to form longer ones. This prevents sample lines of code, and other such "formatted" text from being unduly combined. `-u' `--uniform-spacing' Uniform spacing. Reduce spacing between words to one space, and spacing between sentences to two spaces. `-WIDTH' `-w WIDTH' `--width=WIDTH' Fill output lines up to WIDTH characters (default 75). `fmt' initially tries to make lines about 7% shorter than this, to give it room to balance line lengths. `-p PREFIX' `--prefix=PREFIX' Only lines beginning with PREFIX (possibly preceded by whitespace) are subject to formatting. The prefix and any preceding whitespace are stripped for the formatting and then re-attached to each formatted output line. One use is to format certain kinds of program comments, while leaving the code unchanged. `pr': Paginate or columnate files for printing ============================================== `pr' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, paginating and optionally outputting in multicolumn format; optionally merges all FILEs, printing all in parallel, one per column. Synopsis: pr [OPTION]... [FILE]... By default, a 5-line header is printed at each page: two blank lines; a line with the date, the filename, and the page count; and two more blank lines. A footer of five blank lines is also printed. With the `-F' option, a 3-line header is printed: the leading two blank lines are omitted; no footer is used. The default PAGE_LENGTH in both cases is 66 lines. The default number of text lines changes from 56 (without `-F') to 63 (with `-F'). The text line of the header takes the form `DATE STRING PAGE', with spaces inserted around STRING so that the line takes up the full PAGE_WIDTH. Here, DATE is the date (see the `-D' or `--date-format' option for details), STRING is the centered header string, and PAGE identifies the page number. The `LC_MESSAGES' locale category affects the spelling of PAGE; in the default C locale, it is `Page NUMBER' where NUMBER is the decimal page number. Form feeds in the input cause page breaks in the output. Multiple form feeds produce empty pages. Columns are of equal width, separated by an optional string (default is `space'). For multicolumn output, lines will always be truncated to PAGE_WIDTH (default 72), unless you use the `-J' option. For single column output no line truncation occurs by default. Use `-W' option to truncate lines in that case. The following changes were made in version 1.22i and apply to later versions of `pr': - Brian * Some small LETTER OPTIONS (`-s', `-w') have been redefined for better POSIX compliance. The output of some further cases has been adapted to other Unix systems. These changes are not compatible with earlier versions of the program. * Some NEW CAPITAL LETTER options (`-J', `-S', `-W') have been introduced to turn off unexpected interferences of small letter options. The `-N' option and the second argument LAST_PAGE of `+FIRST_PAGE' offer more flexibility. The detailed handling of form feeds set in the input files requires the `-T' option. * Capital letter options override small letter ones. * Some of the option-arguments (compare `-s', `-e', `-i', `-n') cannot be specified as separate arguments from the preceding option letter (already stated in the POSIX specification). The program accepts the following options. Also see *Note Common options::. `+FIRST_PAGE[:LAST_PAGE]' `--pages=FIRST_PAGE[:LAST_PAGE]' Begin printing with page FIRST_PAGE and stop with LAST_PAGE. Missing `:LAST_PAGE' implies end of file. While estimating the number of skipped pages each form feed in the input file results in a new page. Page counting with and without `+FIRST_PAGE' is identical. By default, counting starts with the first page of input file (not first page printed). Line numbering may be altered by `-N' option. `-COLUMN' `--columns=COLUMN' With each single FILE, produce COLUMN columns of output (default is 1) and print columns down, unless `-a' is used. The column width is automatically decreased as COLUMN increases; unless you use the `-W/-w' option to increase PAGE_WIDTH as well. This option might well cause some lines to be truncated. The number of lines in the columns on each page are balanced. The options `-e' and `-i' are on for multiple text-column output. Together with `-J' option column alignment and line truncation is turned off. Lines of full length are joined in a free field format and `-S' option may set field separators. `-COLUMN' may not be used with `-m' option. `-a' `--across' With each single FILE, print columns across rather than down. The `-COLUMN' option must be given with COLUMN greater than one. If a line is too long to fit in a column, it is truncated. `-c' `--show-control-chars' Print control characters using hat notation (e.g., `^G'); print other nonprinting characters in octal backslash notation. By default, nonprinting characters are not changed. `-d' `--double-space' Double space the output. `-D FORMAT' `--date-format=FORMAT' Format header dates using FORMAT, using the same conventions as for the the command `date +FORMAT'; *Note date invocation::. Except for directives, which start with `%', characters in FORMAT are printed unchanged. You can use this option to specify an arbitrary string in place of the header date, e.g., `--date-format="Monday morning"'. If the `POSIXLY_CORRECT' environment variable is not set, the date format defaults to `%Y-%m-%d %H:%M' (for example, `2001-12-04 23:59'); otherwise, the format depends on the `LC_TIME' locale category, with the default being `%b %e %H:%M %Y' (for example, `Dec 4 23:59 2001'. `-e[IN-TABCHAR[IN-TABWIDTH]]' `--expand-tabs[=IN-TABCHAR[IN-TABWIDTH]]' Expand TABs to spaces on input. Optional argument IN-TABCHAR is the input tab character (default is the TAB character). Second optional argument IN-TABWIDTH is the input tab character's width (default is 8). `-f' `-F' `--form-feed' Use a form feed instead of newlines to separate output pages. The default page length of 66 lines is not altered. But the number of lines of text per page changes from default 56 to 63 lines. `-h HEADER' `--header=HEADER' Replace the filename in the header with the centered string HEADER. When using the shell, HEADER should be quoted and should be separated from `-h' by a space. `-i[OUT-TABCHAR[OUT-TABWIDTH]]' `--output-tabs[=OUT-TABCHAR[OUT-TABWIDTH]]' Replace spaces with TABs on output. Optional argument OUT-TABCHAR is the output tab character (default is the TAB character). Second optional argument OUT-TABWIDTH is the output tab character's width (default is 8). `-J' `--join-lines' Merge lines of full length. Used together with the column options `-COLUMN', `-a -COLUMN' or `-m'. Turns off `-W/-w' line truncation; no column alignment used; may be used with `--sep-string[=STRING]'. `-J' has been introduced (together with `-W' and `--sep-string') to disentangle the old (POSIX-compliant) options `-w' and `-s' along with the three column options. `-l PAGE_LENGTH' `--length=PAGE_LENGTH' Set the page length to PAGE_LENGTH (default 66) lines, including the lines of the header [and the footer]. If PAGE_LENGTH is less than or equal to 10 (or <= 3 with `-F'), the header and footer are omitted, and all form feeds set in input files are eliminated, as if the `-T' option had been given. `-m' `--merge' Merge and print all FILEs in parallel, one in each column. If a line is too long to fit in a column, it is truncated, unless the `-J' option is used. `--sep-string[=STRING]' may be used. Empty pages in some FILEs (form feeds set) produce empty columns, still marked by STRING. The result is a continuous line numbering and column marking throughout the whole merged file. Completely empty merged pages show no separators or line numbers. The default header becomes `DATE PAGE' with spaces inserted in the middle; this may be used with the `-h' or `--header' option to fill up the middle blank part. `-n[NUMBER-SEPARATOR[DIGITS]]' `--number-lines[=NUMBER-SEPARATOR[DIGITS]]' Provide DIGITS digit line numbering (default for DIGITS is 5). With multicolumn output the number occupies the first DIGITS column positions of each text column or only each line of `-m' output. With single column output the number precedes each line just as `-m' does. Default counting of the line numbers starts with the first line of the input file (not the first line printed, compare the `--page' option and `-N' option). Optional argument NUMBER-SEPARATOR is the character appended to the line number to separate it from the text followed. The default separator is the TAB character. In a strict sense a TAB is always printed with single column output only. The TAB-width varies with the TAB-position, e.g. with the left MARGIN specified by `-o' option. With multicolumn output priority is given to `equal width of output columns' (a POSIX specification). The TAB-width is fixed to the value of the first column and does not change with different values of left MARGIN. That means a fixed number of spaces is always printed in the place of the NUMBER-SEPARATOR TAB. The tabification depends upon the output position. `-N LINE_NUMBER' `--first-line-number=LINE_NUMBER' Start line counting with the number LINE_NUMBER at first line of first page printed (in most cases not the first line of the input file). `-o MARGIN' `--indent=MARGIN' Indent each line with a margin MARGIN spaces wide (default is zero). The total page width is the size of the margin plus the PAGE_WIDTH set with the `-W/-w' option. A limited overflow may occur with numbered single column output (compare `-n' option). `-r' `--no-file-warnings' Do not print a warning message when an argument FILE cannot be opened. (The exit status will still be nonzero, however.) `-s[CHAR]' `--separator[=CHAR]' Separate columns by a single character CHAR. The default for CHAR is the TAB character without `-w' and `no character' with `-w'. Without `-s' the default separator `space' is set. `-s[char]' turns off line truncation of all three column options (`-COLUMN'|`-a -COLUMN'|`-m') unless `-w' is set. This is a POSIX-compliant formulation. `-S STRING' `--sep-string[=STRING]' Use STRING to separate output columns. The `-S' option doesn't affect the `-W/-w' option, unlike the `-s' option which does. It does not affect line truncation or column alignment. Without `-S', and with `-J', `pr' uses the default output separator, TAB. Without `-S' or `-J', `pr' uses a `space' (same as `-S" "'). With `-SSTRING', STRING must be nonempty; `--sep-string' with no STRING is equivalent to `--sep-string=""'. On older systems, `pr' instead supports an obsolete option `-S[STRING]', where STRING is optional. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this older usage. To specify an empty STRING portably, use `--sep-string'. `-t' `--omit-header' Do not print the usual header [and footer] on each page, and do not fill out the bottom of pages (with blank lines or a form feed). No page structure is produced, but form feeds set in the input files are retained. The predefined pagination is not changed. `-t' or `-T' may be useful together with other options; e.g.: `-t -e4', expand TAB characters in the input file to 4 spaces but don't make any other changes. Use of `-t' overrides `-h'. `-T' `--omit-pagination' Do not print header [and footer]. In addition eliminate all form feeds set in the input files. `-v' `--show-nonprinting' Print nonprinting characters in octal backslash notation. `-w PAGE_WIDTH' `--width=PAGE_WIDTH' Set page width to PAGE_WIDTH characters for multiple text-column output only (default for PAGE_WIDTH is 72). `-s[CHAR]' turns off the default page width and any line truncation and column alignment. Lines of full length are merged, regardless of the column options set. No PAGE_WIDTH setting is possible with single column output. A POSIX-compliant formulation. `-W PAGE_WIDTH' `--page_width=PAGE_WIDTH' Set the page width to PAGE_WIDTH characters. That's valid with and without a column option. Text lines are truncated, unless `-J' is used. Together with one of the three column options (`-COLUMN', `-a -COLUMN' or `-m') column alignment is always used. The separator options `-S' or `-s' don't affect the `-W' option. Default is 72 characters. Without `-W PAGE_WIDTH' and without any of the column options NO line truncation is used (defined to keep downward compatibility and to meet most frequent tasks). That's equivalent to `-W 72 -J'. The header line is never truncated. `fold': Wrap input lines to fit in specified width ================================================== `fold' writes each FILE (`-' means standard input), or standard input if none are given, to standard output, breaking long lines. Synopsis: fold [OPTION]... [FILE]... By default, `fold' breaks lines wider than 80 columns. The output is split into as many lines as necessary. `fold' counts screen columns by default; thus, a tab may count more than one column, backspace decreases the column count, and carriage return sets the column to zero. The program accepts the following options. Also see *Note Common options::. `-b' `--bytes' Count bytes rather than columns, so that tabs, backspaces, and carriage returns are each counted as taking up one column, just like other characters. `-s' `--spaces' Break at word boundaries: the line is broken after the last blank before the maximum line length. If the line contains no such blanks, the line is broken at the maximum line length as usual. `-w WIDTH' `--width=WIDTH' Use a maximum line length of WIDTH columns instead of 80. On older systems, `fold' supports an obsolete option `-WIDTH'. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-w WIDTH' instead. Output of parts of files ************************ These commands output pieces of the input. `head': Output the first part of files ====================================== `head' prints the first part (10 lines by default) of each FILE; it reads from standard input if no files are given or when given a FILE of `-'. Synopsis: head [OPTION]... [FILE]... If more than one FILE is specified, `head' prints a one-line header consisting of ==> FILE NAME <== before the output for each FILE. The program accepts the following options. Also see *Note Common options::. `-c BYTES' `--bytes=BYTES' Print the first BYTES bytes, instead of initial lines. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-n N' `--lines=N' Output the first N lines. `-q' `--quiet' `--silent' Never print file name headers. `-v' `--verbose' Always print file name headers. On older systems, `head' supports an obsolete option `-COUNTOPTIONS', which is recognized only if it is specified first. COUNT is a decimal number optionally followed by a size letter (`b', `k', `m') as in `-c', or `l' to mean count by lines, or other option letters (`cqv'). POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-c COUNT' or `-n COUNT' instead. `tail': Output the last part of files ===================================== `tail' prints the last part (10 lines by default) of each FILE; it reads from standard input if no files are given or when given a FILE of `-'. Synopsis: tail [OPTION]... [FILE]... If more than one FILE is specified, `tail' prints a one-line header consisting of ==> FILE NAME <== before the output for each FILE. GNU `tail' can output any amount of data (some other versions of `tail' cannot). It also has no `-r' option (print in reverse), since reversing a file is really a different job from printing the end of a file; BSD `tail' (which is the one with `-r') can only reverse files that are at most as large as its buffer, which is typically 32 KiB. A more reliable and versatile way to reverse files is the GNU `tac' command. If any option-argument is a number N starting with a `+', `tail' begins printing with the Nth item from the start of each file, instead of from the end. The program accepts the following options. Also see *Note Common options::. `-c BYTES' `--bytes=BYTES' Output the last BYTES bytes, instead of final lines. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-f' `--follow[=HOW]' Loop forever trying to read more characters at the end of the file, presumably because the file is growing. This option is ignored when reading from a pipe. If more than one file is given, `tail' prints a header whenever it gets output from a different file, to indicate which file that output is from. There are two ways to specify how you'd like to track files with this option, but that difference is noticeable only when a followed file is removed or renamed. If you'd like to continue to track the end of a growing file even after it has been unlinked, use `--follow=descriptor'. This is the default behavior, but it is not useful if you're tracking a log file that may be rotated (removed or renamed, then reopened). In that case, use `--follow=name' to track the named file by reopening it periodically to see if it has been removed and recreated by some other program. No matter which method you use, if the tracked file is determined to have shrunk, `tail' prints a message saying the file has been truncated and resumes tracking the end of the file from the newly-determined endpoint. When a file is removed, `tail''s behavior depends on whether it is following the name or the descriptor. When following by name, tail can detect that a file has been removed and gives a message to that effect, and if `--retry' has been specified it will continue checking periodically to see if the file reappears. When following a descriptor, tail does not detect that the file has been unlinked or renamed and issues no message; even though the file may no longer be accessible via its original name, it may still be growing. The option values `descriptor' and `name' may be specified only with the long form of the option, not with `-f'. `-F' This option is the same as `--follow=name --retry'. That is, tail will attempt to reopen a file when it is removed. Should this fail, tail will keep trying until it becomes accessible again. `--retry' This option is meaningful only when following by name. Without this option, when tail encounters a file that doesn't exist or is otherwise inaccessible, it reports that fact and never checks it again. `--sleep-interval=NUMBER' Change the number of seconds to wait between iterations (the default is 1.0). During one iteration, every specified file is checked to see if it has Historical implementations of `tail' have required that NUMBER be an integer. However, GNU `tail' accepts an arbitrary floating point number. `--pid=PID' When following by name or by descriptor, you may specify the process ID, PID, of the sole writer of all FILE arguments. Then, shortly after that process terminates, tail will also terminate. This will work properly only if the writer and the tailing process are running on the same machine. For example, to save the output of a build in a file and to watch the file grow, if you invoke `make' and `tail' like this then the tail process will stop when your build completes. Without this option, you would have had to kill the `tail -f' process yourself. $ make >& makerr & tail --pid=$! -f makerr If you specify a PID that is not in use or that does not correspond to the process that is writing to the tailed files, then `tail' may terminate long before any FILEs stop growing or it may not terminate until long after the real writer has terminated. Note that `--pid' cannot be supported on some systems; `tail' will print a warning if this is the case. `--max-unchanged-stats=N' When tailing a file by name, if there have been N (default n=5) consecutive iterations for which the size has remained the same, then `open'/`fstat' the file to determine if that file name is still associated with the same device/inode-number pair as before. When following a log file that is rotated, this is approximately the number of seconds between when tail prints the last pre-rotation lines and when it prints the lines that have accumulated in the new log file. This option is meaningful only when following by name. `-n N' `--lines=N' Output the last N lines. `-q' `--quiet' `--silent' Never print file name headers. `-v' `--verbose' Always print file name headers. On older systems, `tail' supports an obsolete option `-COUNTOPTIONS', which is recognized only if it is specified first. COUNT is a decimal number optionally followed by a size letter (`b', `k', `m') as in `-c', or `l' to mean count by lines, or other option letters (`cfqv'). Some older `tail' implementations also support an obsolete option `+COUNT' with the same meaning as `-+COUNT'. POSIX 1003.1-2001 (*note Standards conformance::) does not allow these options; use `-c COUNT' or `-n COUNT' instead. `split': Split a file into fixed-size pieces ============================================ `split' creates output files containing consecutive sections of INPUT (standard input if none is given or INPUT is `-'). Synopsis: split [OPTION] [INPUT [PREFIX]] By default, `split' puts 1000 lines of INPUT (or whatever is left over for the last section), into each output file. The output files' names consist of PREFIX (`x' by default) followed by a group of letters (`aa', `ab', ... by default), such that concatenating the output files in sorted order by file name produces the original input file. If the output file names are exhausted, `split' reports an error without deleting the output files that it did create. The program accepts the following options. Also see *Note Common options::. `-a LENGTH' `--suffix-length=LENGTH' Use suffixes of length LENGTH. The default LENGTH is 2. `-l LINES' `--lines=LINES' Put LINES lines of INPUT into each output file. On older systems, `split' supports an obsolete option `-LINES'. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-l LINES' instead. `-b BYTES' `--bytes=BYTES' Put the first BYTES bytes of INPUT into each output file. Appending `b' multiplies BYTES by 512, `k' by 1024, and `m' by 1048576. `-C BYTES' `--line-bytes=BYTES' Put into each output file as many complete lines of INPUT as possible without exceeding BYTES bytes. For lines longer than BYTES bytes, put BYTES bytes into each output file until less than BYTES bytes of the line are left, then continue normally. BYTES has the same format as for the `--bytes' option. `--verbose' Write a diagnostic to standard error just before each output file is opened. `csplit': Split a file into context-determined pieces ===================================================== `csplit' creates zero or more output files containing sections of INPUT (standard input if INPUT is `-'). Synopsis: csplit [OPTION]... INPUT PATTERN... The contents of the output files are determined by the PATTERN arguments, as detailed below. An error occurs if a PATTERN argument refers to a nonexistent line of the input file (e.g., if no remaining line matches a given regular expression). After every PATTERN has been matched, any remaining input is copied into one last output file. By default, `csplit' prints the number of bytes written to each output file after it has been created. The types of pattern arguments are: `N' Create an output file containing the input up to but not including line N (a positive integer). If followed by a repeat count, also create an output file containing the next LINE lines of the input file once for each repeat. `/REGEXP/[OFFSET]' Create an output file containing the current line up to (but not including) the next line of the input file that contains a match for REGEXP. The optional OFFSET is a `+' or `-' followed by a positive integer. If it is given, the input up to the matching line plus or minus OFFSET is put into the output file, and the line after that begins the next section of input. `%REGEXP%[OFFSET]' Like the previous type, except that it does not create an output file, so that section of the input file is effectively ignored. `{REPEAT-COUNT}' Repeat the previous pattern REPEAT-COUNT additional times. REPEAT-COUNT can either be a positive integer or an asterisk, meaning repeat as many times as necessary until the input is exhausted. The output files' names consist of a prefix (`xx' by default) followed by a suffix. By default, the suffix is an ascending sequence of two-digit decimal numbers from `00' to `99'. In any case, concatenating the output files in sorted order by filename produces the original input file. By default, if `csplit' encounters an error or receives a hangup, interrupt, quit, or terminate signal, it removes any output files that it has created so far before it exits. The program accepts the following options. Also see *Note Common options::. `-f PREFIX' `--prefix=PREFIX' Use PREFIX as the output file name prefix. `-b SUFFIX' `--suffix=SUFFIX' Use SUFFIX as the output file name suffix. When this option is specified, the suffix string must include exactly one `printf(3)'-style conversion specification, possibly including format specification flags, a field width, a precision specifications, or all of these kinds of modifiers. The format letter must convert a binary integer argument to readable form; thus, only `d', `i', `u', `o', `x', and `X' conversions are allowed. The entire SUFFIX is given (with the current output file number) to `sprintf(3)' to form the file name suffixes for each of the individual output files in turn. If this option is used, the `--digits' option is ignored. `-n DIGITS' `--digits=DIGITS' Use output file names containing numbers that are DIGITS digits long instead of the default 2. `-k' `--keep-files' Do not remove output files when errors are encountered. `-z' `--elide-empty-files' Suppress the generation of zero-length output files. (In cases where the section delimiters of the input file are supposed to mark the first lines of each of the sections, the first output file will generally be a zero-length file unless you use this option.) The output file sequence numbers always run consecutively starting from 0, even when this option is specified. `-s' `-q' `--silent' `--quiet' Do not print counts of output file sizes. Summarizing files ***************** These commands generate just a few numbers representing entire contents of files. `wc': Print byte, word, and line counts ======================================= `wc' counts the number of bytes, characters, whitespace-separated words, and newlines in each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: wc [OPTION]... [FILE]... `wc' prints one line of counts for each file, and if the file was given as an argument, it prints the file name following the counts. If more than one FILE is given, `wc' prints a final line containing the cumulative counts, with the file name `total'. The counts are printed in this order: newlines, words, characters, bytes. By default, each count is output right-justified in a 7-byte field with one space between fields so that the numbers and file names line up nicely in columns. However, POSIX requires that there be exactly one space separating columns. You can make `wc' use the POSIX-mandated output format by setting the `POSIXLY_CORRECT' environment variable. By default, `wc' prints three counts: the newline, words, and byte counts. Options can specify that only certain counts be printed. Options do not undo others previously given, so wc --bytes --words prints both the byte counts and the word counts. With the `--max-line-length' option, `wc' prints the length of the longest line per file, and if there is more than one file it prints the maximum (not the sum) of those lengths. The program accepts the following options. Also see *Note Common options::. `-c' `--bytes' Print only the byte counts. `-m' `--chars' Print only the character counts. `-w' `--words' Print only the word counts. `-l' `--lines' Print only the newline counts. `-L' `--max-line-length' Print only the maximum line lengths. `sum': Print checksum and block counts ====================================== `sum' computes a 16-bit checksum for each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: sum [OPTION]... [FILE]... `sum' prints the checksum for each FILE followed by the number of blocks in the file (rounded up). If more than one FILE is given, file names are also printed (by default). (With the `--sysv' option, corresponding file names are printed when there is at least one file argument.) By default, GNU `sum' computes checksums using an algorithm compatible with BSD `sum' and prints file sizes in units of 1024-byte blocks. The program accepts the following options. Also see *Note Common options::. `-r' Use the default (BSD compatible) algorithm. This option is included for compatibility with the System V `sum'. Unless `-s' was also given, it has no effect. `-s' `--sysv' Compute checksums using an algorithm compatible with System V `sum''s default, and print file sizes in units of 512-byte blocks. `sum' is provided for compatibility; the `cksum' program (see next section) is preferable in new applications. `cksum': Print CRC checksum and byte counts =========================================== `cksum' computes a cyclic redundancy check (CRC) checksum for each given FILE, or standard input if none are given or for a FILE of `-'. Synopsis: cksum [OPTION]... [FILE]... `cksum' prints the CRC checksum for each file along with the number of bytes in the file, and the filename unless no arguments were given. `cksum' is typically used to ensure that files transferred by unreliable means (e.g., netnews) have not been corrupted, by comparing the `cksum' output for the received files with the `cksum' output for the original files (typically given in the distribution). The CRC algorithm is specified by the POSIX standard. It is not compatible with the BSD or System V `sum' algorithms (see the previous section); it is more robust. The only options are `--help' and `--version'. *Note Common options::. `md5sum': Print or check message-digests ======================================== `md5sum' computes a 128-bit checksum (or "fingerprint" or "message-digest") for each specified FILE. If a FILE is specified as `-' or if no files are given `md5sum' computes the checksum for the standard input. `md5sum' can also determine whether a file and checksum are consistent. Synopses: md5sum [OPTION]... [FILE]... md5sum [OPTION]... --check [FILE] For each FILE, `md5sum' outputs the MD5 checksum, a flag indicating a binary or text input file, and the filename. If FILE is omitted or specified as `-', standard input is read. The program accepts the following options. Also see *Note Common options::. `-b' `--binary' Treat all input files as binary. This option has no effect on Unix systems, since they don't distinguish between binary and text files. This option is useful on systems that have different internal and external character representations. On MS-DOS and MS-Windows, this is the default. `-c' `--check' Read filenames and checksum information from the single FILE (or from stdin if no FILE was specified) and report whether each named file and the corresponding checksum data are consistent. The input to this mode of `md5sum' is usually the output of a prior, checksum-generating run of `md5sum'. Each valid line of input consists of an MD5 checksum, a binary/text flag, and then a filename. Binary files are marked with `*', text with ` '. For each such line, `md5sum' reads the named file and computes its MD5 checksum. Then, if the computed message digest does not match the one on the line with the filename, the file is noted as having failed the test. Otherwise, the file passes the test. By default, for each valid line, one line is written to standard output indicating whether the named file passed the test. After all checks have been performed, if there were any failures, a warning is issued to standard error. Use the `--status' option to inhibit that output. If any listed file cannot be opened or read, if any valid line has an MD5 checksum inconsistent with the associated file, or if no valid line is found, `md5sum' exits with nonzero status. Otherwise, it exits successfully. `--status' This option is useful only when verifying checksums. When verifying checksums, don't generate the default one-line-per-file diagnostic and don't output the warning summarizing any failures. Failures to open or read a file still evoke individual diagnostics to standard error. If all listed files are readable and are consistent with the associated MD5 checksums, exit successfully. Otherwise exit with a status code indicating there was a failure. `-t' `--text' Treat all input files as text files. This is the reverse of `--binary'. `-w' `--warn' When verifying checksums, warn about improperly formatted MD5 checksum lines. This option is useful only if all but a few lines in the checked input are valid. Operating on sorted files ************************* These commands work with (or produce) sorted files. `sort': Sort text files ======================= `sort' sorts, merges, or compares all the lines from the given files, or standard input if none are given or for a FILE of `-'. By default, `sort' writes the results to standard output. Synopsis: sort [OPTION]... [FILE]... `sort' has three modes of operation: sort (the default), merge, and check for sortedness. The following options change the operation mode: `-c' `--check' Check whether the given files are already sorted: if they are not all sorted, print an error message and exit with a status of 1. Otherwise, exit successfully. `-m' `--merge' Merge the given files by sorting them as a group. Each input file must always be individually sorted. It always works to sort instead of merge; merging is provided because it is faster, in the case where it works. A pair of lines is compared as follows: if any key fields have been specified, `sort' compares each pair of fields, in the order specified on the command line, according to the associated ordering options, until a difference is found or no fields are left. Unless otherwise specified, all comparisons use the character collating sequence specified by the `LC_COLLATE' locale. (1) If any of the global options `bdfgiMnr' are given but no key fields are specified, `sort' compares the entire lines according to the global options. Finally, as a last resort when all keys compare equal (or if no ordering options were specified at all), `sort' compares the entire lines. The last resort comparison honors the `--reverse' (`-r') global option. The `--stable' (`-s') option disables this last-resort comparison so that lines in which all fields compare equal are left in their original relative order. If no fields or global options are specified, `--stable' (`-s') has no effect. GNU `sort' (as specified for all GNU utilities) has no limits on input line length or restrictions on bytes allowed within lines. In addition, if the final byte of an input file is not a newline, GNU `sort' silently supplies one. A line's trailing newline is not part of the line for comparison purposes. Upon any error, `sort' exits with a status of `2'. If the environment variable `TMPDIR' is set, `sort' uses its value as the directory for temporary files instead of `/tmp'. The `--temporary-directory' (`-T') option in turn overrides the environment variable. The following options affect the ordering of output lines. They may be specified globally or as part of a specific key field. If no key fields are specified, global options apply to comparison of entire lines; otherwise the global options are inherited by key fields that do not specify any special options of their own. In pre-POSIX versions of `sort', global options affect only later key fields, so portable shell scripts should specify global options first. `-b' `--ignore-leading-blanks' Ignore leading blanks when finding sort keys in each line. The `LC_CTYPE' locale determines character types. `-d' `--dictionary-order' Sort in "phone directory" order: ignore all characters except letters, digits and blanks when sorting. The `LC_CTYPE' locale determines character types. `-f' `--ignore-case' Fold lowercase characters into the equivalent uppercase characters when comparing so that, for example, `b' and `B' sort as equal. The `LC_CTYPE' locale determines character types. `-g' `--general-numeric-sort' Sort numerically, using the standard C function `strtod' to convert a prefix of each line to a double-precision floating point number. This allows floating point numbers to be specified in scientific notation, like `1.0e-34' and `10e100'. The `LC_NUMERIC' locale determines the decimal-point character. Do not report overflow, underflow, or conversion errors. Use the following collating sequence: * Lines that do not start with numbers (all considered to be equal). * NaNs ("Not a Number" values, in IEEE floating point arithmetic) in a consistent but machine-dependent order. * Minus infinity. * Finite numbers in ascending numeric order (with -0 and +0 equal). * Plus infinity. Use this option only if there is no alternative; it is much slower than `--numeric-sort' (`-n') and it can lose information when converting to floating point. `-i' `--ignore-nonprinting' Ignore nonprinting characters. The `LC_CTYPE' locale determines character types. `-M' `--month-sort' An initial string, consisting of any amount of whitespace, followed by a month name abbreviation, is folded to UPPER case and compared in the order `JAN' < `FEB' < ... < `DEC'. Invalid names compare low to valid names. The `LC_TIME' locale category determines the month spellings. `-n' `--numeric-sort' Sort numerically: the number begins each line; specifically, it consists of optional whitespace, an optional `-' sign, and zero or more digits possibly separated by thousands separators, optionally followed by a decimal-point character and zero or more digits. The `LC_NUMERIC' locale specifies the decimal-point character and thousands separator. Numeric sort uses what might be considered an unconventional method to compare strings representing floating point numbers. Rather than first converting each string to the C `double' type and then comparing those values, `sort' aligns the decimal-point characters in the two strings and compares the strings a character at a time. One benefit of using this approach is its speed. In practice this is much more efficient than performing the two corresponding string-to-double (or even string-to-integer) conversions and then comparing doubles. In addition, there is no corresponding loss of precision. Converting each string to `double' before comparison would limit precision to about 16 digits on most systems. Neither a leading `+' nor exponential notation is recognized. To compare such strings numerically, use the `--general-numeric-sort' (`-g') option. `-r' `--reverse' Reverse the result of comparison, so that lines with greater key values appear earlier in the output instead of later. Other options are: `-o OUTPUT-FILE' `--output=OUTPUT-FILE' Write output to OUTPUT-FILE instead of standard output. If necessary, `sort' reads input before opening OUTPUT-FILE, so you can safely sort a file in place by using commands like `sort -o F F' and `cat F | sort -o F'. On newer systems, `-o' cannot appear after an input file if `POSIXLY_CORRECT' is set, e.g., `sort F -o F'. Portable scripts should specify `-o OUTPUT-FILE' before any input files. `-S SIZE' `--buffer-size=SIZE' Use a main-memory sort buffer of the given SIZE. By default, SIZE is in units of 1024 bytes. Appending `%' causes SIZE to be interpreted as a percentage of physical memory. Appending `K' multiplies SIZE by 1024 (the default), `M' by 1,048,576, `G' by 1,073,741,824, and so on for `T', `P', `E', `Z', and `Y'. Appending `b' causes SIZE to be interpreted as a byte count, with no multiplication. This option can improve the performance of `sort' by causing it to start with a larger or smaller sort buffer than the default. However, this option affects only the initial buffer size. The buffer grows beyond SIZE if `sort' encounters input lines larger than SIZE. `-t SEPARATOR' `--field-separator=SEPARATOR' Use character SEPARATOR as the field separator when finding the sort keys in each line. By default, fields are separated by the empty string between a non-whitespace character and a whitespace character. That is, given the input line ` foo bar', `sort' breaks it into fields ` foo' and ` bar'. The field separator is not considered to be part of either the field preceding or the field following. But note that sort fields that extend to the end of the line, as `-k 2', or sort fields consisting of a range, as `-k 2,3', retain the field separators present between the endpoints of the range. `-T TEMPDIR' `--temporary-directory=TEMPDIR' Use directory TEMPDIR to store temporary files, overriding the `TMPDIR' environment variable. If this option is given more than once, temporary files are stored in all the directories given. If you have a large sort or merge that is I/O-bound, you can often improve performance by using this option to specify directories on different disks and controllers. `-u' `--unique' Normally, output only the first of a sequence of lines that compare equal. For the `--check' (`-c') option, check that no pair of consecutive lines compares equal. `-k POS1[,POS2]' `--key=POS1[,POS2]' Specify a sort field that consists of the part of the line between POS1 and POS2 (or the end of the line, if POS2 is omitted), _inclusive_. Fields and character positions are numbered starting with 1. So to sort on the second field, you'd use `--key=2,2' (`-k 2,2'). See below for more examples. `-z' `--zero-terminated' Treat the input as a set of lines, each terminated by a zero byte (ASCII NUL (Null) character) instead of an ASCII LF (Line Feed). This option can be useful in conjunction with `perl -0' or `find -print0' and `xargs -0' which do the same in order to reliably handle arbitrary pathnames (even those which contain Line Feed characters.) Historical (BSD and System V) implementations of `sort' have differed in their interpretation of some options, particularly `-b', `-f', and `-n'. GNU sort follows the POSIX behavior, which is usually (but not always!) like the System V behavior. According to POSIX, `-n' no longer implies `-b'. For consistency, `-M' has been changed in the same way. This may affect the meaning of character positions in field specifications in obscure cases. The only fix is to add an explicit `-b'. A position in a sort field specified with the `-k' option has the form `F.C', where F is the number of the field to use and C is the number of the first character from the beginning of the field. In a start position, an omitted `.C' stands for the field's first character. In an end position, an omitted or zero `.C' stands for the field's last character. If the `-b' option was specified, the `.C' part of a field specification is counted from the first nonblank character of the field. A sort key position may also have any of the option letters `Mbdfinr' appended to it, in which case the global ordering options are not used for that particular field. The `-b' option may be independently attached to either or both of the start and end positions of a field specification, and if it is inherited from the global options it will be attached to both. Keys may span multiple fields. On older systems, `sort' supports an obsolete origin-zero syntax `+POS1 [-POS2]' for specifying sort keys. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-k' instead. Here are some examples to illustrate various combinations of options. * Sort in descending (reverse) numeric order. sort -nr * Sort alphabetically, omitting the first and second fields. This uses a single key composed of the characters beginning at the start of field three and extending to the end of each line. sort -k 3 * Sort numerically on the second field and resolve ties by sorting alphabetically on the third and fourth characters of field five. Use `:' as the field delimiter. sort -t : -k 2,2n -k 5.3,5.4 Note that if you had written `-k 2' instead of `-k 2,2' `sort' would have used all characters beginning in the second field and extending to the end of the line as the primary _numeric_ key. For the large majority of applications, treating keys spanning more than one field as numeric will not do what you expect. Also note that the `n' modifier was applied to the field-end specifier for the first key. It would have been equivalent to specify `-k 2n,2' or `-k 2n,2n'. All modifiers except `b' apply to the associated _field_, regardless of whether the modifier character is attached to the field-start and/or the field-end part of the key specifier. * Sort the password file on the fifth field and ignore any leading white space. Sort lines with equal values in field five on the numeric user ID in field three. sort -t : -k 5b,5 -k 3,3n /etc/passwd An alternative is to use the global numeric modifier `-n'. sort -t : -n -k 5b,5 -k 3,3 /etc/passwd * Generate a tags file in case-insensitive sorted order. find src -type f -print0 | sort -t / -z -f | xargs -0 etags --append The use of `-print0', `-z', and `-0' in this case means that pathnames that contain Line Feed characters will not get broken up by the sort operation. Finally, to ignore both leading and trailing white space, you could have applied the `b' modifier to the field-end specifier for the first key, sort -t : -n -k 5b,5b -k 3,3 /etc/passwd or by using the global `-b' modifier instead of `-n' and an explicit `n' with the second key specifier. sort -t : -b -k 5,5 -k 3,3n /etc/passwd ---------- Footnotes ---------- (1) If you use a non-POSIX locale (e.g., by setting `LC_ALL' to `en_US'), then `sort' may produce output that is sorted differently than you're accustomed to. In that case, set the `LC_ALL' environment variable to `C'. Note that setting only `LC_COLLATE' has two problems. First, it is ineffective if `LC_ALL' is also set. Second, it has undefined behavior if `LC_CTYPE' (or `LANG', if `LC_CTYPE' is unset) is set to an incompatible value. For example, you get undefined behavior if `LC_CTYPE' is `ja_JP.PCK' but `LC_COLLATE' is `en_US.UTF-8'. `uniq': Uniquify files ====================== `uniq' writes the unique lines in the given `input', or standard input if nothing is given or for an INPUT name of `-'. Synopsis: uniq [OPTION]... [INPUT [OUTPUT]] By default, `uniq' prints the unique lines in a sorted file, i.e., discards all but one of identical successive lines. Optionally, it can instead show only lines that appear exactly once, or lines that appear more than once. The input need not be sorted, but duplicate input lines are detected only if they are adjacent. If you want to discard non-adjacent duplicate lines, perhaps you want to use `sort -u'. Comparisons use the character collating sequence specified by the `LC_COLLATE' locale category. If no OUTPUT file is specified, `uniq' writes to standard output. The program accepts the following options. Also see *Note Common options::. `-f N' `--skip-fields=N' Skip N fields on each line before checking for uniqueness. Fields are sequences of non-space non-tab characters that are separated from each other by at least one space or tab. On older systems, `uniq' supports an obsolete option `-N'. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-f N' instead. `-s N' `--skip-chars=N' Skip N characters before checking for uniqueness. If you use both the field and character skipping options, fields are skipped over first. On older systems, `uniq' supports an obsolete option `+N'. POSIX 1003.1-2001 (*note Standards conformance::) does not allow this; use `-s N' instead. `-c' `--count' Print the number of times each line occurred along with the line. `-i' `--ignore-case' Ignore differences in case when comparing lines. `-d' `--repeated' Print one copy of each duplicate line. `-D' `--all-repeated[=DELIMIT-METHOD]' Print all copies of each duplicate line. This option is useful mainly in conjunction with other options e.g., to ignore case or to compare only selected fields. The optional DELIMIT-METHOD tells how to delimit groups of duplicate lines, and must be one of the following: `none' Do not delimit groups of duplicate lines. This is equivalent to `--all-repeated' (`-D'). `prepend' Output a newline before each group of duplicate lines. `separate' Separate groups of duplicate lines with a single newline. This is the same as using `prepend', except that there is no newline before the first group, and hence may be better suited for output direct to users. Note that when groups are delimited and the input stream contains two or more consecutive blank lines, then the output is ambiguous. To avoid that, filter the input through `tr -s '\n'' to replace each sequence of consecutive newlines with a single newline. This is a GNU extension. `-u' `--unique' Print non-duplicate lines. `-w N' `--check-chars=N' Compare N characters on each line (after skipping any specified fields and characters). By default the entire rest of the lines are compared. `comm': Compare two sorted files line by line ============================================= `comm' writes to standard output lines that are common, and lines that are unique, to two input files; a file name of `-' means standard input. Synopsis: comm [OPTION]... FILE1 FILE2 Before `comm' can be used, the input files must be sorted using the collating sequence specified by the `LC_COLLATE' locale. If an input file ends in a non-newline character, a newline is silently appended. The `sort' command with no options always outputs a file that is suitable input to `comm'. With no options, `comm' produces three column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files. Columns are separated by a single TAB character. The options `-1', `-2', and `-3' suppress printing of the corresponding columns. Also see *Note Common options::. Unlike some other comparison utilities, `comm' has an exit status that does not depend on the result of the comparison. Upon normal completion `comm' produces an exit code of zero. If there is an error it exits with nonzero status. `tsort': Topological sort ========================= `tsort' performs a topological sort on the given FILE, or standard input if no input file is given or for a FILE of `-'. For more details and some history, see *Note tsort background::. Synopsis: tsort [OPTION] [FILE] `tsort' reads its input as pairs of strings, separated by blanks, indicating a partial ordering. The output is a total ordering that corresponds to the given partial ordering. For example tsort <