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SORT(1) NetBSD General Commands Manual SORT(1)
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sort -- sort or merge text files
sort [-bdfHilmnrSsu] [-k kstart[,kend]] [-o output] [-R char] [-T dir]
[-t char] [file ...]
sort -C|-c [-bdfilnru] [-k kstart[,kend] [-t char]] [-R char] [file]
The sort utility sorts text files by lines. Comparisons are based on one
or more sort keys extracted from each line of input, and are performed
lexicographically. By default, if keys are not given, sort regards each
input line as a single field.
The following options are available:
-C Identical to -c without the error messages in the case of
-c 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, sort returns 0. sort -c pro-
duces no output. See also -u.
-H Ignored for compatibility with earlier versions of sort.
-m Merge only; the input files are assumed to be pre-sorted.
-o output The argument given is the name of an output file to be used
instead of the standard output. This file can be the same as
one of the input files.
-S Don't use stable sort. Default is to use stable sort.
-s Use stable sort, keeps records with equal keys in their orig-
inal order. This is the default. Provided for compatibility
with other sort implementations only.
-T dir Use dir as the directory for temporary files. The default is
the value specified in the environment variable TMPDIR or
/tmp if TMPDIR is not defined.
-u Unique: suppress all but one in each set of lines having
equal keys. If used with the -c option, check that there are
no lines with duplicate keys.
The following options, which should be given before any -k options, over-
ride the default ordering rules. When ordering options appear indepen-
dent of, and before, key field specifications, the requested field order-
ing rules are applied globally to all sort keys. When attached to a spe-
cific key (see -k), the ordering options override all global ordering
options for that key.
-d Only blank space and alphanumeric characters are used in mak-
-f Considers all lowercase characters that have uppercase equiv-
alents to be the same for purposes of comparison.
-i Ignore all non-printable characters.
-l Sort by the string length of the field, not by the field
-n An initial numeric string, consisting of optional blank
space, optional plus or minus sign, and zero or more digits
(including decimal point) is sorted by arithmetic value.
(The -n option no longer implies the -b option.)
-r Reverse the sense of comparisons.
The treatment of field separators can be altered using these options:
-b Ignores leading blank space when determining the start and
end of a restricted sort key. A -b option specified before
the first -k option applies globally to all -k options. Oth-
erwise, the -b option can be attached independently to each
field argument of the -k option (see below). Note that the
-b option has no effect unless key fields are specified.
Designates the starting position, kstart, and optional ending
position, kend, of a key field. The -k option replaces the
obsolescent options +pos1 and -pos2.
-R char char is used as the record separator character. This should
be used with discretion; -R <alphanumeric> usually produces
undesirable results. If char is not a single character, then
it specifies the value of the desired record separator as an
integer specified in any of the normal NNN, 0ooo, or 0xXXX
ways, or as an octal value preceded by \. Caution: do not
attempt to specify Ctl-A as ``-R 1'' which will not do what
was intended at all! The default record separator is new-
-t char char is used as the field separator character. The initial
char is not considered to be part of a field when determining
key offsets (see below). 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; further, the initial
blank space is considered part of a field when determining
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 minimal sequence of characters followed by a
field separator or a newline character. By default, the first blank
space of a sequence of blank spaces acts as the field separator. All
blank spaces in a sequence of blank spaces are considered as part of the
next field; 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 kstart[,kend] argument. A missing kend
argument defaults to the end of a line.
The arguments kstart and kend have the form m.n and can be followed by
one or more of the letters b, d, f, i, l, n, and r, which correspond to
the options discussed above. A kstart position specified by m.n (m, n >
0) is interpreted as the nth character in the mth field. A missing .n in
kstart 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 charac-
ter in the mth field; m.1b refers to the first non-blank character in the
A kend position specified by m.n is interpreted as the nth character
(including separators) 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 obsolescent option
+v-1.x-1-w-1.y; when y is omitted, -k v.x,w is synonymous with
+v-1.x-1-w+1.0. The obsolescent +pos1 -pos2 option is still supported,
except for -w.0b, which has no -k equivalent.
sort compares records by comparing the key fields selected by -k argu-
ments, from first given to last, until discovering a difference. If
there are no -k arguments, the whole record is treated as a single key.
After exhausting the -k arguments, if no difference has been found, then
the result depends upon the -u and -S option settings. With -u the
records are considered identical, and one is suppressed. Otherwise with
-s set (default) the records are left in their original order, or with -S
(posix mode) the whole record is considered as a tie breaker.
If the following environment variable exists, it is used by sort.
TMPDIR sort uses the contents of the TMPDIR environment vari-
able as the path in which to store temporary files.
/tmp/sort.* Default temporary files.
outputNUMBER Temporary file which is used for output if output
already exists. Once sorting is finished, this file
replaces output (via link(2) and unlink(2)).
Sort exits with one of the following values:
0 Normal behavior.
1 On disorder (or non-uniqueness) with the -c (or -C) option.
2 An error occurred.
comm(1), join(1), uniq(1), qsort(3), radixsort(3)
A sort command appeared in Version 1 AT&T UNIX. This sort implementation
appeared in 4.4BSD and is used since NetBSD 1.6.
Posix requires the locale's thousands separator be ignored in numbers.
It may be faster to sort very large files in pieces and then explicitly
This sort has no limits on input line length (other than imposed by
available memory) or any restrictions on bytes allowed within lines.
To protect data sort -o calls link(2) and unlink(2), and thus fails on
Input files should be text files. If file doesn't end with record sepa-
rator (which is typically newline), the sort utility silently supplies
The current sort uses lexicographic radix sorting, which requires that
sort keys be kept in memory (as opposed to previous versions which used
quick and merge sorts and did not.) Thus performance depends highly on
efficient choice of sort keys, and the -b option and the kend argument of
the -k option should be used whenever possible. Similarly, sort -k1f is
equivalent to sort -f and may take twice as long.
NetBSD 9.2 September 1, 2019 NetBSD 9.2