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SORT(1) DragonFly 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] [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.
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 produces 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" version
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. This file can be the same as one of the input files.
-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 processed 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 an 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
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. 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. 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 (human-
Ignore all non-printable characters.
-M, --month-sort, --sort=month
Sort by month abbreviations. Unknown strings are considered
smaller than the month names.
-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 decimal point and possible
-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 randomized 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 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 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.
-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 when 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 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 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, however,
the initial blank space is considered part of a field when
determining key offsets. To use NUL as field separator, use -t
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
Set the maximum number of execution threads. Default number
equals to the number of CPUs.
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
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', 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.
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
LC_ALL Locale settings that override all of the above locale
settings. This environment 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.
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")
The flags [-ghRMSsTVz] are extensions to the POSIX specification.
All long options are extensions to the specification, some of them are
provided for compatibility with GNU versions and some of them are own
The old key notations *pos1 and -pos2 come from older versions of sort
and are still supported 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 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 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 slowest but the
correct collation order is always respected. As 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.
DragonFly 5.7-DEVELOPMENT December 2, 2019 DragonFly 5.7-DEVELOPMENT