sort, merge, or sequence check text and
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 ‘
-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 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.
-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.
- Write the output to the output file instead of the standard output. This file can be the same as one of the input files.
- 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
sortmay use up to about 90% of available memory. If the input is too big to fit into the memory buffer, temporary files are used.
- 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.
- Store temporary files in the directory dir. The
default path is the value of the environment variable
TMPDIRor /tmp if
TMPDIRis not defined.
- Unique: suppress all but one in each set of lines having equal keys. This
option implies a stable sort (see below). If used with
sortalso checks that there are no lines with duplicate keys.
The following options override the default ordering rules. If
ordering options appear before the first
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 comparisons.
- Consider all lowercase characters that have uppercase equivalents to be the same for purposes of comparison.
- 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
-nbut it has a significant performance drawback.
- 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
- Ignore all non-printable characters.
- Sort by month abbreviations. Unknown strings are considered smaller than valid month names.
- 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 are ignored.
- 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
--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.
$ 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:
- Ignore leading blank space when determining the start and end of a
restricted sort key (see
-bis specified before the first
-koption, it applies globally to all key specifications. Otherwise,
-bcan be attached independently to each field argument of the key specifications. Note that
-bshould not appear after
-k, and that it has no effect unless key fields are specified.
- Define a restricted sort key that has the starting position
field1, and optional ending position
field2 of a key field. The
-koption may be specified multiple times, in which case subsequent keys are compared after earlier keys compare equal. The
-koption replaces the obsolete options
-pos2, but the old notation is also supported.
- 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).
-tis 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 character.
- Specify maximum number of files that can be opened by
sortat 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
-doption, it must decompress standard input to standard output. If program fails,
sortwill exit with an error. The compress(1) and gzip(1) utilities meet these requirements.
- Print some extra information about the sorting process to the standard output.
- 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
- 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.
- 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
- 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
Fields are specified by the
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
r, which correspond to the options discussed above.
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
.1’, indicating the first character
of the mth field; if the
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
v.x,w.y is synonymous with the obsolete option
y is omitted,
-k v.x,w is synonymous with
-w.0. The obsolete
-pos2 option is still
supported, except for
which has no
- Path to the directory in which temporary files will be stored. Note that
TMPDIRmay be overridden by the
- Temporary files.
sort utility exits with one of the
- Successfully sorted the input files or if used with
-c, the input file already met the sorting criteria.
- On disorder (or non-uniqueness) with the
- An error occurred.
comm(1), join(1), uniq(1)
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
The flags [
-gHhiMRSsTVz] are extensions to
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
option to appear after the file is supported for
compatibility with older versions of
The historic key notations
-pos2 are supported for
compatibility with older versions of
sort but their
use is highly discouraged.
sort command appeared in
Version 1 AT&T UNIX.
Oleg Moskalenko <firstname.lastname@example.org>
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
results in much better performance than
-g so its
use is encouraged whenever possible.