SORT(1) | General Commands Manual | SORT(1)

# NAME

`sort` — sort, merge, or sequence check text and binary files

# SYNOPSIS

`sort` | [`-bCcdfgHhiMmnRrsuVz`] [`-k` field1[,field2]] [`-o` output] [`-S` size] [`-T` dir] [`-t` char] [file ...]

# DESCRIPTION

The `sort` utility sorts the lines of text or binary files. A line is a record separated from the subsequent record by a newline (default) or NUL ‘`\0`’ character (`-z` option). A record can contain any printable or unprintable characters. Comparisons are based on one or more sort keys extracted from each line according to the specified command line options. By default, `sort` uses entire lines for comparison and sorts in ascii(7) order.

If no file is specified, or if file is ‘-’, the standard input is used.

The options are as follows:

`-C`, `--check`=`silent`|`quiet`
  Check that the single input file is sorted. If it is, exit 0; if it's not, exit 1. In either case, produce no output.
`-c`, `--check`
  Like `-C`, but additionally write a message to stderr if the input file is not sorted.
`-m`, `--merge`
  Merge only; the input files are assumed to be pre-sorted. If they are not sorted, the output order is undefined.
`-o` output, `--output`=output
  Write the output to the output file instead of the standard output. This file can be the same as one of the input files.
`-S` size, `--buffer-size`=size
  Use a memory buffer no larger than size. The modifiers %, b, K, M, G, T, P, E, Z, and Y can be used. If no memory limit is specified, `sort` may use up to about 90% of available memory. If the input is too big to fit into the memory buffer, temporary files are used.
`-s`
  Stable sort; maintains the original record order of records that have an equal key. This is a non-standard feature, but it is widely accepted and used.
`-T` dir, `--temporary-directory`=dir
  Store temporary files in the directory dir. The default path is the value of the environment variable `TMPDIR` or /tmp if `TMPDIR` is not defined.
`-u`, `--unique`
  Unique: suppress all but one in each set of lines having equal keys. This option implies `-s`. If used with `-C` or `-c`, `sort` also checks that there are no lines with duplicate keys.

The following options override the default ordering rules. If ordering options appear before the first `-k` option, they apply globally to all sort keys. When attached to a specific key (see `-k`), the ordering options override all global ordering options for that key. Note that the ordering options intended to apply globally should not appear after `-k` or results may be unexpected.

`-d`, `--dictionary-order`
  Consider only blank spaces and alphanumeric characters in comparisons.
`-f`, `--ignore-case`
  Consider all lowercase characters that have uppercase equivalents to be the same for purposes of comparison.
`-g`, `--general-numeric-sort`, `--sort`=`general-numeric`
  Use an initial numeric string as the key and sort numerically. As opposed to `-n`, this option handles general floating point numbers. It has a more permissive format than that allowed by `-n` but it has a significant performance drawback.
`-h`, `--human-numeric-sort`, `--sort`=`human-numeric`
  Use an initial numeric string with an optional SI suffix as the key. Sorts first by numeric sign (negative, zero, or positive); then by SI suffix (either empty, or `k' or `K', or one of `MGTPEZY', in that order); and finally by numeric value. The SI suffix must immediately follow the number. For example, '12345K' sorts before '1M', because M is "larger" than K. This sort option is useful for sorting the output of a single invocation of a df(1) command with `-h` or `-H` options (human-readable).
`-i`, `--ignore-nonprinting`
  Ignore all non-printable characters.
`-M`, `--month-sort`, `--sort`=`month`
  Sort by month abbreviations. Unknown strings are considered smaller than valid month names.
`-n`, `--numeric-sort`, `--sort`=`numeric`
  Use an initial numeric string as the key, consisting of optional blank space, an optional minus sign, and zero or more digits including an optional decimal point, and sort numerically. Leading blank characters are ignored.
`-R`, `--random-sort`, `--sort`=`random`
  Sort lines in random order. This is a random permutation of the inputs with the exception that equal keys sort together. It is implemented by hashing the input keys and sorting the hash values. The hash function is randomized with data from arc4random_buf(3), or by file content if one is specified via `--random-source`. If multiple sort fields are specified, the same random hash function is used for all of them.
`-r`, `--reverse`
  Sort in reverse order.
`-V`, `--version-sort`
  This option is intended to sort strings that contain version numbers but it can be used for other purposes as well, for example to sort IPv4 addresses in dotted quad notation.

  When comparing two strings, both strings are split into substrings such that the first and every other odd-numbered substring consists of non-digit characters only, while every even-numbered substring consists of digits only. These substrings are compared in turn from left to right until a difference is found. The first substring can be empty; all others cannot.

  Non-digit substrings are compared alphabetically, with upper case letters sorting before lower case letters, letters sorting before non-letters, and non-letters sorting in ascii(7) order. Substrings consisting of digits are compared as integer numbers.

  At the end of each string, zero or more suffixes that start with a dot, consist only of letters, digits, and tilde characters, and do not start with a digit are ignored, equivalent to the regular expression "(\.([A-Za-z~][A-Za-z0-9~]*)?)*". This is intended for ignoring filename suffixes such as “.tar.bz2”.

  In the following example, the first substring is "sort-" and the other odd-numbered substrings are all ".":

      $ ls sort* | sort -V
      sort-1.022.tgz
      sort-1.23.tgz
      sort-1.23.1.tgz
      sort-1.024.tgz
      sort-1.024.003.
      sort-1.024.003.tgz
      sort-1.024.07.tgz
      sort-1.024.009.tgz

The treatment of field separators can be altered using these options:

`-b`, `--ignore-leading-blanks`
  Ignore leading blank space when determining the start and end of a restricted sort key (see `-k`). If `-b` is specified before the first `-k` option, it applies globally to all key specifications. Otherwise, `-b` can be attached independently to each field argument of the key specifications. Note that `-b` should not appear after `-k`, and that it has no effect unless key fields are specified.
`-k` field1[,field2], `--key`=field1[,field2]
  Define a restricted sort key that has the starting position field1, and optional ending position field2 of a key field. The `-k` option may be specified multiple times, in which case subsequent keys are compared after earlier keys compare equal. The `-k` option replaces the obsolete options `+`pos1 and `-`pos2, but the old notation is also supported.
`-t` char, `--field-separator`=char
  Use char as the field separator character. The initial char is not considered to be part of a field when determining key offsets. Each occurrence of char is significant (for example, “charchar” delimits an empty field). If `-t` is not specified, the default field separator is a sequence of blank-space characters, and consecutive blank spaces do not delimit an empty field; further, the initial blank space is considered part of a field when determining key offsets. To use NUL as field separator, use `-t` '\0'.
`-z`, `--zero-terminated`
  Use NUL as the record separator. By default, records in the files are expected to be separated by the newline characters. With this option, NUL (‘`\0`’) is used as the record separator character.

Other options:

`--batch-size`=num
  Specify maximum number of files that can be opened by `sort` at once. This option affects behavior when having many input files or using temporary files. The minimum value is 2. The default value is 16.
`--compress-program`=program
  Use program to compress temporary files. When invoked with no arguments, program must compress standard input to standard output. When called with the `-d` option, it must decompress standard input to standard output. If program fails, `sort` will exit with an error. The compress(1) and gzip(1) utilities meet these requirements.
`--debug`
  Print some extra information about the sorting process to the standard output.
`--files0-from`=filename
  Take the input file list from the file filename. The file names must be separated by NUL (like the output produced by the command “find ... -print0”).
`--heapsort`
  Try to use heap sort, if the sort specifications allow. This sort algorithm cannot be used with `-u` and `-s`.
`--help`
  Print the help text and exit.
`-H`, `--mergesort`
  Use mergesort. This is a universal algorithm that can always be used, but it is not always the fastest.
`--mmap`
  Try to use file memory mapping system call. It may increase speed in some cases.
`--qsort`
  Try to use quick sort, if the sort specifications allow. This sort algorithm cannot be used with `-u` and `-s`.
`--radixsort`
  Try to use radix sort, if the sort specifications allow. The radix sort can only be used for trivial locales (C and POSIX), and it cannot be used for numeric or month sort. Radix sort is very fast and stable.
`--random-source`=filename
  For random sort, the contents of filename are used as the source of the ‘seed’ data for the hash function. Two invocations of random sort with the same seed data produce the same result if the input is also identical. By default, the arc4random_buf(3) function is used instead.
`--version`
  Print the version and exit.

A field is defined as a maximal sequence of characters other than the field separator and record separator (newline by default). Initial blank spaces are included in the field unless `-b` has been specified; the first blank space of a sequence of blank spaces acts as the field separator and is included in the field (unless `-t` is specified). For example, by default all blank spaces at the beginning of a line are considered to be part of the first field.

Fields are specified by the `-k` field1[,field2] option. If field2 is missing, the end of the key defaults to the end of the line.

The arguments field1 and field2 have the form m.n (m,n > 0) and can be followed by one or more of the modifiers `b`, `d`, `f`, `i`, `n`, `g`, `M` and `r`, which correspond to the options discussed above. When `b` is specified, it applies only to field1 or field2 where it is specified while the rest of the modifiers apply to the whole key field regardless if they are specified only with field1 or field2 or both. A field1 position specified by m.n is interpreted as the nth character from the beginning of the mth field. A missing .n in field1 means ‘`.1`’, indicating the first character of the mth field; if the `-b` option is in effect, n is counted from the first non-blank character in the mth field; m.1b refers to the first non-blank character in the mth field. 1.n refers to the nth character from the beginning of the line; if n is greater than the length of the line, the field is taken to be empty.

nth positions are always counted from the field beginning, even if the field is shorter than the number of specified positions. Thus, the key can really start from a position in a subsequent field.

A field2 position specified by m.n is interpreted as the nth character (including separators) from the beginning of the mth field. A missing .n indicates the last character of the mth field; m = 0 designates the end of a line. Thus the option `-k` v.x,w.y is synonymous with the obsolete option `+`v-1.x-1 `-`w-1.y; when y is omitted, `-k` v.x,w is synonymous with `+`v-1.x-1 `-`w.0. The obsolete `+`pos1 `-`pos2 option is still supported, except for `-`w.0b, which has no `-k` equivalent.

# ENVIRONMENT

`TMPDIR`
  Path to the directory in which temporary files will be stored. Note that `TMPDIR` may be overridden by the `-T` option.

# FILES

/tmp/.bsdsort.PID.*
  Temporary files.

# EXIT STATUS

The `sort` utility exits with one of the following values:

0
  Successfully sorted the input files or if used with `-C` or `-c`, the input file already met the sorting criteria.
1
  On disorder (or non-uniqueness) with the `-C` or `-c` options.
2
  An error occurred.

# SEE ALSO

comm(1), join(1), uniq(1)

# STANDARDS

The `sort` utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification, except that it ignores the user's locale(1) and always assumes `LC_ALL`=C.

The flags [`-gHhiMRSsTVz`] are extensions to that specification.

All long options are extensions to the specification. Some are provided for compatibility with GNU `sort`, others are specific to this implementation.

Some implementations of `sort` honor the `-b` option even when no key fields are specified. This implementation follows historic practice and IEEE Std 1003.1-2008 (“POSIX.1”) in only honoring `-b` when it precedes a key field.

The historic practice of allowing the `-o` option to appear after the file is supported for compatibility with older versions of `sort`.

The historic key notations `+`pos1 and `-`pos2 are supported for compatibility with older versions of `sort` but their use is highly discouraged.

# HISTORY

A `sort` command appeared in Version 1 AT&T UNIX.

# AUTHORS

Gabor Kovesdan <gabor@FreeBSD.org>
Oleg Moskalenko <mom040267@gmail.com>

# CAVEATS

This implementation of `sort` has no limits on input line length (other than imposed by available memory) or any restrictions on bytes allowed within lines.

The performance depends highly on efficient choice of sort keys and key complexity. The fastest sort is on whole lines, with option `-s`. For the key specification, the simpler to process the lines the faster the search will be.

When sorting by arithmetic value, using `-n` results in much better performance than `-g` so its use is encouraged whenever possible.

April 1, 2025 | Debian