SORT(1) General Commands Manual SORT(1)
sort - sort or merge files
sort [ -_________x ] [ +pos1 [ -pos2 ] ] ... [ -o name ] [ -T directory ] [ name ] ...
Sort sorts lines of all the named files together and writes the result on the standard output. The name `-' means the standard input. If
no input files are named, the standard input is sorted.
The default sort key is an entire line. Default ordering is lexicographic by bytes in machine collating sequence. The ordering is
affected globally by the following options, one or more of which may appear.
b Ignore leading blanks (spaces and tabs) in field comparisons.
d `Dictionary' order: only letters, digits and blanks are significant in comparisons.
f Fold upper case letters onto lower case.
i Ignore characters outside the ASCII range 040-0176 in nonnumeric comparisons.
n An initial numeric string, consisting of optional blanks, optional minus sign, and zero or more digits with optional decimal point, is
sorted by arithmetic value. Option n implies option b.
r Reverse the sense of comparisons.
tx `Tab character' separating fields is x.
The notation +pos1 -pos2 restricts a sort key to a field beginning at pos1 and ending just before pos2. Pos1 and pos2 each have the form
m.n, optionally followed by one or more of the flags bdfinr, where m tells a number of fields to skip from the beginning of the line and n
tells a number of characters to skip further. If any flags are present they override all the global ordering options for this key. If the
b option is in effect n is counted from the first nonblank in the field; b is attached independently to pos2. A missing .n means .0; a
missing -pos2 means the end of the line. Under the -tx option, fields are strings separated by x; otherwise fields are nonempty nonblank
strings separated by blanks.
When there are multiple sort keys, later keys are compared only after all earlier keys compare equal. Lines that otherwise compare equal
are ordered with all bytes significant.
These option arguments are also understood:
c Check that the input file is sorted according to the ordering rules; give no output unless the file is out of sort.
m Merge only, the input files are already sorted.
o The next argument is the name of an output file to use instead of the standard output. This file may be the same as one of the
T The next argument is the name of a directory in which temporary files should be made.
u Suppress all but one in each set of equal lines. Ignored bytes and bytes outside keys do not participate in this comparison.
Print in alphabetical order all the unique spellings in a list of words. Capitalized words differ from uncapitalized.
sort -u +0f +0 list
Print the password file (passwd(5)) sorted by user id number (the 3rd colon-separated field).
sort -t: +2n /etc/passwd
Print the first instance of each month in an already sorted file of (month day) entries. The options -um with just one input file make the
choice of a unique representative from a set of equal lines predictable.
sort -um +0 -1 dates
/usr/tmp/stm*, /tmp/* first and second tries for temporary files
uniq(1), comm(1), rev(1), join(1)
Comments and exits with nonzero status for various trouble conditions and for disorder discovered under option -c.
Very long lines are silently truncated.
7th Edition April 29, 1985 SORT(1)
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SORT(1) General Commands Manual SORT(1)
sort - sort lines of text files
sort [-cmus] [-t separator] [-o output-file] [-T tempdir] [-bdfiMnr] [+POS1 [-POS2]] [-k POS1[,POS2]] [file...]
This manual page documents the GNU version of sort. sort sorts, merges, or compares all the lines from the given files, or the standard
input if no files are given. A file name of `-' means standard input. By default, sort writes the results to the standard output.
sort has three modes of operation: sort (the default), merge, and check for sortedness. The following options change the operation mode:
-c 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.
-m Merge the given files by sorting them as a group. Each input file should already 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.
If any of the global options Mbdfinr are given but no key fields are specified, sort compares the entire lines according to the global
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.
GNU sort 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.
If the environment variable TMPDIR is set, sort uses it as the directory in which to put temporary files instead of the default, /tmp. The
-T tempdir option is another way to select the directory for temporary files; it 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.
-b Ignore leading blanks when finding sort keys in each line.
-d Sort in `phone directory' order: ignore all characters except letters, digits and blanks when sorting.
-f Fold lower case characters into the equivalent upper case characters when sorting so that, for example, `b' is sorted the same way
-i Ignore characters outside the ASCII range 040-0176 octal (inclusive) when sorting.
-M An initial string, consisting of any amount of white space, followed by three letters abbreviating a month name, is folded to UPPER
case and compared in the order `JAN' < `FEB' < ... < `DEC.' Invalid names compare low to valid names.
-n Compare according to arithmetic value an initial numeric string consisting of optional white space, an optional - sign, and zero or
more digits, optionally followed by a decimal point and zero or more digits.
-r Reverse the result of comparison, so that lines with greater key values appear earlier in the output instead of later.
Other options are:
Write output to output-file instead of to the standard output. If output-file is one of the input files, sort copies it to a tempo-
rary file before sorting and writing the output to output-file.
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 to say, 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 it.
-u For the default case or the -m option, only output the first of a sequence of lines that compare equal. For the -c option, check
that no pair of consecutive lines compares equal.
Specify a field within each line to use as a sorting key. The field consists of the portion of the line starting at POS1 and up to
(but not including) POS2 (or to the end of the line if POS2 is not given). The fields and character positions are numbered starting
An alternate syntax for specifying sorting keys. The fields and character positions are numbered starting with 1.
A position 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). The .c part of a position may be omitted in which case it is taken to
be the first character in the field. If the -b option has been given, the .c part of a field specification is counted from the first non-
blank character of the field (for +pos) or from the first nonblank character following the previous field (for -pos).
A +pos or -pos argument 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 speci-
fication, and if it is inherited from the global options it will be attached to both. If a -n or -M option is used, thus implying a -b
option, the -b option is taken to apply to both the +pos and the -pos parts of a key specification. Keys may span multiple fields.
In addition, when GNU sort is invoked with exactly one argument, the following options are recognized:
--help Print a usage message on standard output and exit successfully.
Print version information on standard output then exit successfully.
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 specifica-
tions in obscure cases. If this bites you the fix is to add an explicit -b.
The different meaning of field numbers depending on whether -k is used is confusing. It's all POSIX's fault!
GNU Text Utilities SORT(1)