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
sort [option]... [file]...
sort has three modes of operation: sort (the default), merge,
and check for sortedness. The following options change the operation
A pair of lines is compared as follows: if any key fields have been
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.
If any of the global options `Mbdfinr' are given but no key fields
sort compares the entire lines according to the
Finally, as a last resort when all keys compare equal (or if no
ordering options were specified at all),
sort compares the lines
byte by byte in machine collating sequence. The last resort comparison
honors the `-r' global option. The `-s' (stable) 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, `-s' has no effect.
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.
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
`-T tempdir' option in turn overrides the environment
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.
10e100. Use this option only if there is no alternative; it is much slower than `-n' and numbers with too many significant digits will be compared as if they had been truncated. In addition, numbers outside the range of representable double precision floating point numbers are treated as if they were zeroes; overflow and underflow are not reported.
sort -nuses what might be considered an unconventional method to compare strings representing floating point numbers. Rather than first converting each string to the C
doubletype and then comparing those values, sort aligns the decimal points 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
doublebefore 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 `-g' option.
Other options are:
sortcopies it to a temporary file before sorting and writing the output to output-file.
sortbreaks it into fields ` foo' and ` bar'. The field separator is not considered to be part of either the field preceding or the field following.
In addition, when GNU
sort is invoked with exactly one argument,
options `--help' and `--version' are recognized. See section Common options.
Historical (BSD and System V) implementations of
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' or `+' 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 (for `+pos') or from the end of the previous field (for `-pos'). If the `.c' is omitted, it is taken to be the first character in the field. If the `-b' option was specified, the `.c' part of a field specification is counted from the first nonblank character of the field (for `+pos') or from the first nonblank character following the previous field (for `-pos').
A sort key option 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 `+pos' and `-pos' parts of a field specification, and if it is inherited from the global options it will be attached to both. Keys may span multiple fields.
Here are some examples to illustrate various combinations of options. In them, the POSIX `-k' option is used to specify sort keys rather than the obsolete `+pos1-pos2' syntax.
sort -nrSort 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 -t : -k 2,2n -k 5.3,5.4Note 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 -t : -k 5b,5 -k 3,3n /etc/passwdAn alternative is to use the global numeric modifier `-n'.
sort -t : -n -k 5b,5 -k 3,3 /etc/passwd
find src -type f -print0 | sort -t / -z -f | xargs -0 etags --appendThe use of `-print0', `-z', and `-0' in this case mean 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/passwdor 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
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