sort

Sort text files.
Sort, merge, or compare all the lines from the files given (or standard input.)

Syntax
      sort [options] [file...]
      sort [options]... --files0-from=F

Ordering Options

   -b, --ignore-leading-blanks
       Ignore leading blanks. 
   -d, --dictionary-order
       Consider only blanks and alphanumeric characters.
   -f, --ignore-case
       Fold lower case to upper case characters.
   -g, --general-numeric-sort
       Compare according to general numerical value.
   -i, --ignore-nonprinting
       Consider only printable characters.
   -M, --month-sort
       Compare (unknown) < 'JAN' < ... < 'DEC'
   -h, --human-numeric-sort
       Compare human readable numbers (e.g., 2K 1G).
   -n, --numeric-sort
       Compare according to string numerical value.
   -R, --random-sort
       Sort by random hash of keys.
   --random-source=FILE
       Get random bytes from FILE.
   -r, --reverse
       Reverse the result of comparisons.
   --sort=WORD
       Sort according to WORD: general-numeric -g, human-numeric -h, month -M, numeric -n, random -R, version -V 
   -V, --version-sort
       Natural sort of (version) numbers within text.

Other options:

   --batch-size=NMERGE
       Merge at most NMERGE inputs at once; for more use temp files.
   -c, --check, --check=diagnose-first
       Check for sorted input; do not sort.
   -C, --check=quiet, --check=silent
       Like -c, but do not report first bad line.
   --compress-program=PROG
       Compress temporaries with PROG; decompress them with PROG -d 
   --files0-from=F
       Read input from the files specified by NUL-terminated names in file F; If F is - then read names from standard input.
   -k, --key=POS1[,POS2]
       Start a key at POS1 (origin 1), end it at POS2 (default end of line).
   -m, --merge
       Merge already sorted files; do not sort.
   -o, --output=FILE
       Write result to FILE instead of standard output.
   -s, --stable
       Stabilize sort by disabling last-resort comparison.
   -S, --buffer-size=SIZE
       Use SIZE for main memory buffer.
   -t, --field-separator=SEP
       Use SEP instead of non-blank to blank transition.
   -T, --temporary-directory=DIR
       Use DIR for temporaries, not $TMPDIR or /tmp; multiple options specify multiple directories.
   -u, --unique
       With -c, check for strict ordering; without -c, output only the first of an equal run.
   -z, --zero-terminated
       End lines with 0 byte, not newline.
   --help
       Display help and exit.
   --version
       Output version information and exit.

Write sorted concatenation of all FILE(s) to standard output.
Mandatory arguments to long options are mandatory for short options too.

POS is F[.C][OPTS], where F is the field number and C the character position in the field; both are origin 1.

If neither -t nor -b is in effect, characters in a field are counted from the beginning of the preceding whitespace.

OPTS is one or more single-letter ordering options, which override global ordering options for that key. If no key is given, use the entire line as the key.

SIZE may be followed by the following multiplicative suffixes: % 1% of memory, b 1, K 1024 (default), and so on for M, G, T, P, E, Z, Y.

With no FILE, or when FILE is -, read standard input.

*** WARNING *** The locale specified by the environment affects sort order.
Set LC_ALL=C to get the traditional sort order that uses native byte values.

How lines are compared

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.

If any of the global options 'Mbdfinr' 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 '-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' (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 part of the line for comparison purposes; for example, with no options in an ASCII locale, a line starting with a tab sorts before an empty line because tab precedes newline in the ASCII collating sequence.

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 variable.

Notes

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 can 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 can 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 can 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 can span multiple fields.

Examples

Character sort:

$ sort countries.txt

Numeric sort:

$ sort -n numbers.txt

To sort the file below on the third field (area code):

Jim Alchin 212121 Seattle
Bill Gates 404404 Seattle
Steve Jobs 246810 Nevada
Scott Neally 212277 Los Angeles

$ sort -k 3,3 people.txt> sorted.txt

or using the 'old' syntax:
$ sort +2 -3 people.txt> sorted2.txt

To sort the same file on the 4th column and supress duplicates: (should return 3 rows)
$ sort -u -k 4,4 people.txt> sorted3.txt

In the remaining examples, the POSIX '-k' option is used to specify sort keys rather than the obsolete '+POS1-POS2' syntax.

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 -k3

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 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/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

A file name of '-' means standard input.

By default, sort writes the results to the standard output.

"We never sit anything out. We are cups, constantly and quietly being filled. The trick is, knowing how to tip ourselves over and let the Beautiful Stuff out" ~ Ray Bradbury

Related linux commands

head - Output the first part of file(s).
nl - Number lines and write files.
printf - Format and print data.
Equivalent Windows commands: SORT - Sort input.