path: root/static/netbsd/man1/sort.1

.\"	$NetBSD: sort.1,v 1.51 2026/01/23 14:06:09 jkoshy Exp $
.\"
.\" Copyright (c) 2000-2003 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Ben Harris and Jaromir Dolecek.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.\" Copyright (c) 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)sort.1	8.1 (Berkeley) 6/6/93
.\"
.Dd January 23, 2026
.Dt SORT 1
.Os
.Sh NAME
.Nm sort
.Nd sort, merge or check the sortedness of text files
.Sh SYNOPSIS
.Nm
.Op Fl bdfHilnrSsu
.Oo
.Fl k
.Ar kstart Ns Oo Cm \&, Ns Ar kend Oc Ar ...
.Oc
.Op Fl o Ar output
.Op Fl R Ar char
.Op Fl T Ar dir
.Op Fl t Ar char
.Op Ar
.Nm
.Fl m
.Op Fl bdfHilnrSsu
.Oo
.Fl k
.Ar kstart Ns Oo Cm \&, Ns Ar kend Oc Ar ...
.Oc
.Op Fl o Ar output
.Op Fl R Ar char
.Op Fl T Ar dir
.Op Fl t Ar char
.Op Ar
.Nm
.Fl C Ns | Ns Fl c
.Op Fl bdfilnru
.Oo
.Fl k
.Ar kstart Ns Oo Cm \&, Ns Ar kend Oc Ar ...
.Oc
.Op Fl R Ar char
.Op Fl t Ar char
.Op Ar file
.Sh DESCRIPTION
The
.Nm
utility performs one of three operations on its input files:
.Bl -enum
.It
If none of the options
.Fl C ,
.Fl c
or
.Fl m
are specified, the
.Nm
utility will sort the lines of the specified input files together and
write the result to the specified output.
.It
If the
.Fl m
option is specified, the
.Nm
utility will merge the lines of the specified input files and
write the result to the specified output.
The input files are expected to be presorted for this mode of
operation.
.It
If either of the
.Fl C
or
.Fl c
options are specified, the
.Nm
utility will indicate by its exit status whether a single input file
is correctly sorted.
.El
.Pp
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,
.Nm
regards each input line as a single field.
.Pp
The following options are available:
.Bl -tag -width Fl
.It Fl C
Identical to
.Fl c
without the error messages in the case of unsorted input.
.It Fl c
Check that the single input file is sorted.
If the file is not sorted,
.Nm
produces the appropriate error messages and exits with code 1; otherwise,
.Nm
returns 0.
.Nm
.Fl c
produces no output.
See also
.Fl u .
.It Fl H
Ignored for compatibility with earlier versions of
.Nm .
.It Fl m
Merge only; the input files are assumed to be pre-sorted.
.It Fl o Ar output
The argument given is the name of an
.Ar output
file to be used instead of the standard output.
This file can be the same as one of the input files.
.It Fl S
Don't use stable sort.
Default is to use stable sort.
.It Fl s
Use stable sort, keeps records with equal keys in their original order.
This is the default.
Provided for compatibility with other
.Nm
implementations only.
.It Fl T Ar dir
Use
.Ar dir
as the directory for temporary files.
The default is the value specified in the environment variable
.Ev TMPDIR or
.Pa /tmp
if
.Ev TMPDIR
is not defined.
.It Fl u
Unique: suppress all but one in each set of lines having equal keys.
If used with the
.Fl c
option, check that there are no lines with duplicate keys.
.El
.Pp
The following options,
which should be given before any
.Fl k
options, override the default ordering rules.
When ordering options appear independent of,
and before, key field specifications,
the requested field ordering rules are
applied globally to all sort keys.
When attached to a specific key (see
.Fl k ) ,
the ordering options override
all global ordering options for that key.
.Bl -tag -width Fl
.It Fl d
Only blank space and alphanumeric characters
.\" according
.\" to the current setting of LC_CTYPE
are used
in making comparisons.
.It Fl f
Considers all lowercase characters that have uppercase
equivalents to be the same for purposes of comparison.
.It Fl i
Ignore all non-printable characters.
.It Fl l
Sort by the string length of the field, not by the field itself.
.It Fl n
An initial numeric string, consisting of optional blank space, optional
plus or minus sign, and zero or more digits
.Pq including decimal point
.\" with
.\" optional radix character and thousands
.\" separator
.\" (as defined in the current locale),
is sorted by arithmetic value.
.Po
The
.Fl n
option no longer implies the
.Fl b
option
.Pc .
.It Fl r
Reverse the sense of comparisons.
.El
.Pp
The treatment of field separators can be altered using these options:
.Bl -tag -width Fl
.It Fl b
Ignores leading blank space when determining the start
and end of a restricted sort key.
A
.Fl b
option specified before the first
.Fl k
option applies globally to all
.Fl k
options.
Otherwise, the
.Fl b
option can be attached independently to each field argument of the
.Fl k
option (see below).
Note that the
.Fl b
option has no effect unless key fields are specified.
.It Fl k Ar kstart Ns Op Cm \&, Ns Ar kend
Designates the starting position,
.Ar kstart ,
and optional ending position,
.Ar kend ,
of a key field.
The
.Fl k
option replaces the obsolescent options
.Cm \(pl Ns Ar pos1
and
.Fl Ns Ar pos2 .
.It Fl R Ar char
.Ar char
is used as the record separator character.
This should be used with discretion;
.Fl R Aq Ar 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
.Ar ddd ,
.Li 0 Ns Ar ooo ,
or
.Li 0x Ns Ar hh
ways,
or as an octal value preceded by a backslash
.Pq Ql \e .
.Em Caution :
do not attempt to specify
.Ql \e^A
.Pq Tn SOH
as
.Sq Fl R Li 1
which will not do what was intended at all!
The default record separator is newline.
.It Fl t Ar char
.Ar char
is used as the field separator character.
The initial
.Ar char
is not considered to be part of a field when determining
key offsets (see below).
Each occurrence of
.Ar char
is significant
.Po
for example,
.Sq Ao Ar char Ac Ns Aq Ar char
delimits an empty field
.Pc .
If
.Fl t
is not specified, the default field separator is a sequence of
blank-space characters, and consecutive blank spaces do
.Em not
delimit an empty field; further, the initial blank space
.Em is
considered part of a field when determining key offsets.
.El
.Pp
The following operands are available:
.Bl -tag -width Ar
.It Ar file
The pathname of a file to be sorted, merged, or checked.
If no
.Ar file
operands are specified, or if
a
.Ar file
operand is
.Fl ,
the standard input is used.
.El
.Pp
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.
.Pp
Fields are specified
by the
.Fl k
.Ar kstart Ns Op Cm \&, Ns Ar kend
argument.
A missing
.Ar kend
argument defaults to the end of a line.
.Pp
The arguments
.Ar kstart
and
.Ar kend
have the form
.Ar m Ns Op Cm \&. Ns Ar n
.Pq Ar m\^ , n No > 0
and can be followed by one or more of the letters
.Cm b , d , f , i ,
.Cm l , n ,
and
.Cm r ,
which correspond to the options discussed above.
.Pp
A
.Ar kstart
position specified by
.Ar m Ns Cm \&. Ns Ar n
is interpreted as the
.Ar n Ap th
character in the
.Ar m Ap th
field.
A missing
.Cm \&. Ns Ar n
in
.Ar kstart
means
.Sq Cm \&.1 ,
indicating the first character of the
.Ar m Ap th
field; if the
.Fl b
option is in effect,
.Ar n
is counted from the first non-blank character in the
.Ar m Ap th
field;
.Ar m Ns Cm \&.1b
refers to the first non-blank character in the
.Ar m Ap th
field.
.Pp
A
.Ar kend
position specified by
.Ar m Ns Cm \&. Ns Ar n
is interpreted as
the
.Ar n Ap th
character
.Pq including separators
of the
.Ar m Ap th
field.
A missing
.Cm \&. Ns Ar n
indicates the last character of the
.Ar m Ap th
field;
.Ar m
= \&0
designates the end of a line.
.Pp
Thus the option
.Fl k
.Sm off
.Ar v Cm \&. Ar x Cm \&, Ar w Cm \&. Ar y
.Sm on
is synonymous with the obsolescent options
.Sm off
.Cm \(pl Ar v\^ Li \-1 Cm \&. Ar x\^ Li \-1
.Sm on
.Sm off
.Fl Ar w\^ Li \-1 Cm \&. Ar y .
.Sm on
.
When
.Ar y
is omitted,
.Fl k
.Sm off
.Ar v Cm \&. Ar x Cm \&, Ar w
.Sm on
is synonymous with
.Sm off
.Cm \(pl Ar v\^ Li \-1 Cm \&. Ar x\^ Li \-1
.Sm on
.Sm off
.Fl Ar w\^ Li +1 Cm \&.0 .
.Sm on
The obsolescent
.Cm \(pl Ns Ar pos1
.Fl Ns Ar pos2
options are still supported, except for
.Fl Ar w Ns Cm \&.0b ,
which has no
.Fl k
equivalent.
.Pp
.Nm
compares records by comparing the key fields selected by
.Fl k
arguments,
from first given to last,
until discovering a difference.
If there are no
.Fl k
arguments, the whole record is treated as a single key.
After exhausting the
.Fl k
arguments, if no difference has been found,
then the result depends upon the
.Fl u
and
.Fl S
option settings.
With
.Fl u
the records are considered identical, and one is suppressed.
Otherwise with
.Fl s
set (default) the records are left in their original order,
or with
.Fl S
(POSIX mode) the whole record is considered as a tie breaker.
.\"
.\" If you fail to understand why it doesn't matter which order
.\" the records are output when they are wholly identical, there
.\" is nothing that this man page can say that wll help!
.\"
.Sh ENVIRONMENT
If the following environment variable exists, it is used by
.Nm .
.Bl -tag -width Ev
.It Ev TMPDIR
.Nm
uses the contents of the
.Ev TMPDIR
environment variable as the path in which to store
temporary files.
.El
.Sh FILES
.Bl -tag -width ".Ar output\^ Ns Aq Li NUMBER" -compact
.It Pa /tmp/sort.*
Default temporary files.
.It Ar output\^ Ns Aq Li NUMBER
Temporary file which is used for output if
.Ar output
already exists.
Once sorting is finished, this file replaces
.Ar output
.Po
via
.Xr link 2
and
.Xr unlink 2
.Pc .
.El
.Sh EXAMPLES
To silently check if the lines in a file are sorted lexicographically,
use:
.Pp
.Dl $ sort -C file
.Pp
To merge three pre-sorted files and write the merged result to stdout,
use:
.Pp
.Dl $ sort -m file1 file2 file3
.Pp
To sort lines lexicographically using the second whitespace-separated
field of each line as the sort key preserving leading whitespace in
the sort key, use:
.Bd -literal -offset indent
$ sort -k 2 <<EOF
  aa bb
  ab   bb
EOF
  ab   bb
  aa bb
$
.Ed
.Pp
To sort lines lexicographically using the second whitespace-separated
field on each line as the sort key ignoring any leading whitespace in
the sort key, use:
.Bd -literal -offset indent
$ sort -k 2b <<EOF
  aa bb
  ab   bb
EOF
  aa bb
  ab   bb
$
.Ed
.Pp
To sort lines numerically, using the second whitespace-separated field
on each line as the sort key, starting the sort key at the second
non-blank character within the field, use:
.Bd -literal -offset indent
$ sort -k 2.2nb <<EOF
  aa  X42
  ab Y24
EOF
  ab Y24
  aa  X42
$
.Ed
.Pp
To sort lines numerically with a sort key starting on the second
character of the second whitespace delimited field and to further sort
lines with equal keys lexicographically on the first whitespace
delimited field, use:
.Bd -literal -offset indent
$ sort -k 2.2n -k 1 <<EOF
  ab X42
  aa Y42
  ac Z43
EOF
  aa Y42
  ab X42
  ac Z43
.Ed
.Pp
To lexicographically sort the lines of a file in reverse order, use:
.Pp
.Dl $ sort -r -f file
.
.Sh EXIT STATUS
Sort exits with one of the following values:
.Bl -tag -width flag -compact
.It 0
Normal behavior.
.It 1
On disorder (or non-uniqueness) with the
.Fl c
(or
.Fl C )
option.
.It 2
An error occurred.
.El
.Sh SEE ALSO
.Xr comm 1 ,
.Xr join 1 ,
.Xr uniq 1 ,
.Xr qsort 3 ,
.Xr radixsort 3
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .
This
.Nm
implementation appeared in
.Bx 4.4
and is used since
.Nx 1.6 .
.Sh BUGS
POSIX requires the locale's thousands separator be ignored in numbers.
.Pp
It may be faster to sort very large files in pieces and then explicitly
merge them.
.Sh NOTES
This
.Nm
has no limits on input line length (other than imposed by available
memory) or any restrictions on bytes allowed within lines.
.Pp
To protect data
.Nm
.Fl o
calls
.Xr link 2
and
.Xr unlink 2 ,
and thus fails on protected directories.
.Pp
Input files should be text files.
If file doesn't end with record separator (which is typically newline), the
.Nm
utility silently supplies one.
.Pp
The current
.Nm
uses lexicographic radix sorting, which requires that sort keys be
kept in memory
.Po
as opposed to previous versions which used quick and merge sorts and
did not
.Pc .
Thus performance depends highly on efficient choice of sort keys, and the
.Fl b
option and the
.Ar kend
argument of the
.Fl k
option should be used whenever possible.
Similarly,
.Nm
.Fl k1f
is equivalent to
.Nm
.Fl f
and may take twice as long.