SORT(1) BSD General Commands Manual SORT(1)
sort -- sort or merge records (lines) of text and binary files
sort [-bcCdfghiRMmnrsuVz] [-k field1[,field2]] [-S memsize] [-T dir] [-t char] [-o output]
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
The command line options are as follows:
-c, --check, -C, --check=silent|quiet
Check that the single input file is sorted. If the file is not sorted, sort pro-
duces the appropriate error messages and exits with code 1, otherwise returns 0. If
-C or --check=silent is specified, sort produces no output. This is a "silent" ver-
sion of -c.
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
Print the output to the output file instead of the standard output.
-S size, --buffer-size=size
Use size for the maximum size of the memory buffer. Size modifiers
%,b,K,M,G,T,P,E,Z,Y can be used. If a memory limit is not explicitly specified,
sort takes up to about 90% of available memory. If the file size is too big to fit
into the memory buffer, the temporary disk files are used to perform the sorting.
-T dir, --temporary-directory=dir
Store temporary files in the directory dir. The default path is the value of the
environment variable TMPDIR or /var/tmp if TMPDIR is not defined.
Unique keys. Suppress all lines that have a key that is equal to an already pro-
cessed one. This option, similarly to -s, implies a stable sort. If used with -c
or -C, sort also checks that there are no lines with duplicate keys.
-s Stable sort. This option maintains the original record order of records that have
and equal key. This is a non-standard feature, but it is widely accepted and used.
Print the version and silently exits.
--help Print the help text and silently exits.
The following options override the default ordering rules. When ordering options appear
independently of key field specifications, they apply globally to all sort keys. When
attached to a specific key (see -k), the ordering options override all global ordering
options for the key they are attached to.
Ignore leading blank characters when comparing lines.
Consider only blank spaces and alphanumeric characters in comparisons.
Convert all lowercase characters to their uppercase equivalent before comparison,
that is, perform case-independent sorting.
-g, --general-numeric-sort, --sort=general-numeric
Sort by general numerical value. As opposed to -n, this option handles general
floating points, which have a much permissive format than those allowed by -n, but
it has a significant performance drawback.
-h, --human-numeric-sort, --sort=human-numeric
Sort by numerical value, but take into account the SI suffix, if present. Sort
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
Ignore all non-printable characters.
-M, --month-sort, --sort=month
Sort by month abbreviations. Unknown strings are considered smaller than the month
-n, --numeric-sort, --sort=numeric
Sort fields numerically by arithmetic value. Fields are supposed to have optional
blanks in the beginning, an optional minus sign, zero or more digits (including dec-
imal point and possible thousand separators).
-R, --random-sort, --sort=random
Sort by a random order. This is a random permutation of the inputs except that the
equal keys sort together. It is implemented by hashing the input keys and sorting
the hash values. The hash function is chosen randomly. The hash function is ran-
domized by /dev/random content, or by file content if it is specified by
--random-source. Even 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 VER-
SION 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 C locale, the locale environment setting is ignored.
$ 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. -b.
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 when earlier keys compare equal.
The -k option replaces the obsolete options +pos1 and -pos2, but the old notation is
-t char, --field-separator=char
Use char as a field separator character. The initial char is not considered to be
part of a field when determining key offsets. Each occurrence of char is signifi-
cant (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, however, the initial blank space is con-
sidered part of a field when determining key offsets. To use NUL as field separa-
tor, use -t '\0'.
Use NUL as record separator. By default, records in the files are supposed to be
separated by the newline characters. With this option, NUL ('\0') is used as a
record separator character.
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 default
value is 16.
Use PROGRAM to compress temporary files. PROGRAM must compress standard input to
standard output, when called without arguments. When called with argument -d it
must decompress standard input to standard output. If PROGRAM fails, sort must exit
with error. An example of PROGRAM that can be used here is bzip2.
In random sort, the file content is used as the source of the 'seed' data for the
hash function choice. Two invocations of random sort with the same seed data will
use the same hash function and will produce the same result if the input is also
identical. By default, file /dev/random is used.
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 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.
Use mergesort. This is a universal algorithm that can always be used, but it is not
always the fastest.
Try to use quick sort, if the sort specifications allow. This sort algorithm cannot
be used with -u and -s.
Try to use heap sort, if the sort specifications allow. This sort algorithm cannot
be used with -u and -s.
--mmap Try to use file memory mapping system call. It may increase speed in some cases.
The following operands are available:
file The pathname of a file to be sorted, merged, or checked. If no file operands are
specified, or if a file operand is -, the standard input is used.
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, 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] command-line 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', indicat-
ing 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 sub-
A field2 position specified by m.n is interpreted as the nth character (including separa-
tors) 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.
LC_COLLATE Locale settings to be used to determine the collation for sorting records.
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
LC_NUMERIC Locale settings that determine the number format used in numeric sort.
LC_TIME Locale settings that determine the month format used in month sort.
LC_ALL Locale settings that override all of the above locale settings. This environ-
ment variable can be used to set all these settings to the same value at once.
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.
NLSPATH Path to NLS catalogs.
TMPDIR Path to the directory in which temporary files will be stored. Note that TMPDIR
may be overridden by the -T option.
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.
/var/tmp/.bsdsort.PID.* Temporary files.
/dev/random Default seed file for the random sort.
The sort utility shall exit 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'') specification.
The flags [-ghRMSsTVz] are extensions to the POSIX specification.
All long options are extensions to the specification, some of them are provided for compati-
bility with GNU versions and some of them are own extensions.
The old key notations +pos1 and -pos2 come from older versions of sort and are still sup-
ported but their use is highly discouraged.
A sort command first appeared in Version 3 AT&T UNIX.
Gabor Kovesdan <gabor@FreeBSD.org>,
Oleg Moskalenko <firstname.lastname@example.org>
This implementation of sort has no limits on input line length (other than imposed by avail-
able memory) or any restrictions on bytes allowed within lines.
The performance depends highly on locale settings, efficient choice of sort keys and key
complexity. The fastest sort is with locale C, on whole lines, with option -s. In general,
locale C is the fastest, then single-byte locales follow and multi-byte locales as the slow-
est but the correct collation order is always respected. As 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.
BSD July 3, 2012 BSD