SORT(1) General Commands Manual SORT(1)
sort - sort, merge, or sequence check text and binary files
sort [-bCcdfgHhiMmnRrsuVz] [-k field1[,field2]] [-o output] [-S size]
[-T dir] [-t char] [file ...]
The sort utility sorts text and binary files by lines. 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 of input, and are performed lexicographically,
according to the current locale's collating rules and the specified
command-line options that can tune the actual sorting behavior. By
default, if keys are not given, sort uses entire lines for comparison.
If no file is specified, or if file is `-', the standard input is used.
The options are as follows:
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.
Like -C, but additionally write a message to stderr if the input
file is not sorted.
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
Unique: suppress all but one in each set of lines having equal
keys. This option implies a stable sort (see below). If used
with -C or -c, sort also checks that there are no lines with
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.
Consider only blank spaces and alphanumeric characters in
Consider all lowercase characters that have uppercase equivalents
to be the same for purposes of comparison.
-g, --general-numeric-sort, --sort=general-numeric
Sort by general numerical value. As opposed to -n, this option
handles general floating points. It has a more permissive format
than that allowed by -n but it has a significant performance
-h, --human-numeric-sort, --sort=human-numeric
Sort by numerical value, but take into account the SI suffix, if
present. 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 'df' command with -h or -H options (human-
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
An initial numeric string, consisting of optional blank space,
optional minus sign, and zero or more digits (including decimal
point) is sorted by arithmetic value. Leading blank characters
-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.
Sort in reverse order.
Sort version numbers. The input lines are treated as file names
in form PREFIX VERSION SUFFIX, where SUFFIX matches the regular
expression "(.([A-Za-z~][A-Za-z0-9~]*)?)*". The files are
compared by their prefixes and versions (leading zeros are
ignored in version numbers, see example below). If an input
string does not match the pattern, then it is compared using the
byte compare function. All string comparisons are performed in
the C locale.
$ ls sort* | sort -V
The treatment of field separators can be altered using these options:
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
-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
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
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.
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
Print some extra information about the sorting process to the
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").
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.
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.
Try to use quick sort, if the sort specifications allow. This
sort algorithm cannot be used with -u and -s.
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.
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 will use produce the same
result if the input is also identical. By default, the
arc4random_buf(3) function is used instead.
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.
If defined -t will not override the locale numeric symbols,
that is, thousand separators and decimal separators. By
default, if we specify -t with the same symbol as the
thousand separator or decimal point, the symbol will be
treated as the field separator. Older behavior was less
definite: the symbol was treated as both field separator and
numeric separator, simultaneously. This environment variable
enables the old behavior.
LANG Used as a last resort to determine different kinds of locale-
specific behavior if neither the respective environment
variable nor LC_ALL are set.
LC_ALL Locale settings that override all of the other locale
settings. This environment variable can be used to set all
these settings to the same value at once.
LC_COLLATE Locale settings to be used to determine the collation for
LC_CTYPE Locale settings to be used to case conversion and
classification of characters, that is, which characters are
considered whitespaces, etc.
Locale settings that determine the language of output
messages that sort prints out.
LC_NUMERIC Locale settings that determine the number format used in
LC_TIME Locale settings that determine the month format used in month
TMPDIR Path to the directory in which temporary files will be
stored. Note that TMPDIR may be overridden by the -T option.
/tmp/.bsdsort.PID.* Temporary files.
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.
comm(1), join(1), uniq(1)
The sort utility is compliant with the IEEE Std 1003.1-2008 ("POSIX.1")
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
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
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
A sort command appeared in Version 3 AT&T UNIX.
Gabor Kovesdan <gabor@FreeBSD.org>
Oleg Moskalenko <email@example.com>
This implementation of sort has no limits on input line length (other
than imposed by available memory) or any restrictions on bytes allowed
The performance depends highly on locale settings, efficient choice of
sort keys and key complexity. The fastest sort is with the C locale, on
whole lines, with option -s. In general, the C locale is the fastest,
followed by single-byte locales with multi-byte locales being the
slowest. The correct collation order respected in all cases. For the
key specification, the simpler to process the lines the faster the search
When sorting by arithmetic value, using -n results in much better
performance than -g so its use is encouraged whenever possible.
OpenBSD 6.2 June 10, 2017 OpenBSD 6.2
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