.\"	$OpenBSD: sort.1,v 1.69 2025/04/01 00:18:28 schwarze Exp $
.\"
.\" Copyright (c) 1991, 1993
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.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\" are met:
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.\"    may be used to endorse or promote products derived from this software
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.\"     @(#)sort.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: April 1 2025 $
.Dt SORT 1
.Os
.Sh NAME
.Nm sort
.Nd sort, merge, or sequence check text and binary files
.Sh SYNOPSIS
.Nm sort
.Op Fl bCcdfgHhiMmnRrsuVz
.Op Fl k Ar field1 Ns Op , Ns Ar field2
.Op Fl o Ar output
.Op Fl S Ar size
.Op Fl T Ar dir
.Op Fl t Ar char
.Op Ar
.Sh DESCRIPTION
The
.Nm
utility sorts the lines of text or binary files.
A line is a record separated from the subsequent record by a
newline (default) or NUL
.Ql \e0
character
.Po
.Fl z
option
.Pc .
A record can contain any printable or unprintable characters.
Comparisons are based on one or more sort keys extracted from
each line according to the specified command line options.
By default,
.Nm
uses entire lines for comparison and sorts in
.Xr ascii 7
order.
.Pp
If no
.Ar file
is specified, or if
.Ar file
is
.Sq - ,
the standard input is used.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl C , Fl Fl check Ns = Ns Cm silent Ns | Ns Cm quiet
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.
.It Fl c , Fl Fl check
Like
.Fl C ,
but additionally write a message to
.Em stderr
if the input file is not sorted.
.It Fl m , Fl Fl merge
Merge only; the input files are assumed to be pre-sorted.
If they are not sorted, the output order is undefined.
.It Fl o Ar output , Fl Fl output Ns = Ns Ar output
Write the output to the
.Ar output
file instead of the standard output.
This file can be the same as one of the input files.
.It Fl S Ar size , Fl Fl buffer-size Ns = Ns Ar size
Use a memory buffer no larger than
.Ar size .
The modifiers %, b, K, M, G, T, P, E, Z, and Y can be used.
If no memory limit is specified,
.Nm
may use up to about 90% of available memory.
If the input is too big to fit into the memory buffer,
temporary files are used.
.It Fl s
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.
.It Fl T Ar dir , Fl Fl temporary-directory Ns = Ns Ar dir
Store temporary files in the directory
.Ar dir .
The default path is the value of the environment variable
.Ev TMPDIR
or
.Pa /tmp
if
.Ev TMPDIR
is not defined.
.It Fl u , Fl Fl unique
Unique: suppress all but one in each set of lines having equal keys.
This option implies
.Fl s .
If used with
.Fl C
or
.Fl c ,
.Nm
also checks that there are no lines with duplicate keys.
.El
.Pp
The following options override the default ordering rules.
If ordering options appear before the first
.Fl k
option, they apply 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.
Note that the ordering options intended to apply globally should not
appear after
.Fl k
or results may be unexpected.
.Bl -tag -width indent
.It Fl d , Fl Fl dictionary-order
Consider only blank spaces and alphanumeric characters in comparisons.
.It Fl f , Fl Fl ignore-case
Consider all lowercase characters that have uppercase
equivalents to be the same for purposes of comparison.
.It Fl g , Fl Fl general-numeric-sort , Fl Fl sort Ns = Ns Cm general-numeric
Use an initial numeric string as the key and sort numerically.
As opposed to
.Fl n ,
this option handles general floating point numbers.
It has a more
permissive format than that allowed by
.Fl n
but it has a significant performance drawback.
.It Fl h , Fl Fl human-numeric-sort , Fl Fl sort Ns = Ns Cm human-numeric
Use an initial numeric string with an optional SI suffix as the key.
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 a
.Xr df 1
command with
.Fl h
or
.Fl H
options (human-readable).
.It Fl i , Fl Fl ignore-nonprinting
Ignore all non-printable characters.
.It Fl M , Fl Fl month-sort , Fl Fl sort Ns = Ns Cm month
Sort by month abbreviations.
Unknown strings are considered smaller than valid month names.
.It Fl n , Fl Fl numeric-sort , Fl Fl sort Ns = Ns Cm numeric
Use an initial numeric string as the key, consisting of optional
blank space, an optional minus sign, and zero or more digits including
an optional decimal point, and sort numerically.
Leading blank characters are ignored.
.It Fl R , Fl Fl random-sort , Fl Fl sort Ns = Ns Cm random
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
.Xr arc4random_buf 3 ,
or by file content if one is specified via
.Fl Fl random-source .
If multiple sort fields are specified,
the same random hash function is used for all of them.
.It Fl r , Fl Fl reverse
Sort in reverse order.
.It Fl V , Fl Fl version-sort
This option is intended to sort strings that contain version numbers
but it can be used for other purposes as well, for example to sort
IPv4 addresses in dotted quad notation.
.Pp
When comparing two strings, both strings are split into substrings
such that the first and every other odd-numbered substring
consists of non-digit characters only,
while every even-numbered substring consists of digits only.
These substrings are compared in turn from left to right
until a difference is found.
The first substring can be empty; all others cannot.
.Pp
Non-digit substrings are compared alphabetically, with upper case
letters sorting before lower case letters, letters sorting before
non-letters, and non-letters sorting in
.Xr ascii 7
order.
Substrings consisting of digits are compared as integer numbers.
.Pp
At the end of each string, zero or more suffixes that start with a dot,
consist only of letters, digits, and tilde characters, and do not
start with a digit are ignored, equivalent to the regular expression
"(\e.([A-Za-z~][A-Za-z0-9~]*)?)*".
This is intended for ignoring filename suffixes such as
.Dq .tar.bz2 .
.Pp
In the following example, the first substring is
.Qq sort\-
and the other odd-numbered substrings are all
.Qq \&. :
.Bd -literal -offset indent
$ 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
.Ed
.El
.Pp
The treatment of field separators can be altered using these options:
.Bl -tag -width indent
.It Fl b , Fl Fl ignore-leading-blanks
Ignore leading blank space when determining the start
and end of a restricted sort key (see
.Fl k ) .
If
.Fl b
is specified before the first
.Fl k
option, it applies globally to all key specifications.
Otherwise,
.Fl b
can be attached independently to each
.Ar field
argument of the key specifications.
Note that
.Fl b
should not appear after
.Fl k ,
and that it has no effect unless key fields are specified.
.It Xo
.Fl k Ar field1 Ns Op , Ns Ar field2 ,
.Fl Fl key Ns = Ns Ar field1 Ns Op , Ns Ar field2
.Xc
Define a restricted sort key that has the starting position
.Ar field1 ,
and optional ending position
.Ar field2
of a key field.
The
.Fl k
option may be specified multiple times,
in which case subsequent keys are compared after earlier keys compare equal.
The
.Fl k
option replaces the obsolete options
.Cm \(pl Ns Ar pos1
and
.Fl Ns Ar pos2 ,
but the old notation is also supported.
.It Fl t Ar char , Fl Fl field-separator Ns = Ns Ar char
Use
.Ar char
as the field separator character.
The initial
.Ar char
is not considered to be part of a field when determining key offsets.
Each occurrence of
.Ar char
is significant (for example,
.Dq Ar charchar
delimits an empty field).
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.
To use NUL as field separator, use
.Fl t
\(aq\e0\(aq.
.It Fl z , Fl Fl zero-terminated
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
.Pq Ql \e0
is used as the record separator character.
.El
.Pp
Other options:
.Bl -tag -width indent
.It Fl Fl batch-size Ns = Ns Ar num
Specify maximum number of files that can be opened by
.Nm
at once.
This option affects behavior when having many input files or using
temporary files.
The minimum value is 2.
The default value is 16.
.It Fl Fl compress-program Ns = Ns Ar program
Use
.Ar program
to compress temporary files.
When invoked with no arguments,
.Ar program
must compress standard input to standard output.
When called with the
.Fl d
option, it must decompress standard input to standard output.
If
.Ar program
fails,
.Nm
will exit with an error.
The
.Xr compress 1
and
.Xr gzip 1
utilities meet these requirements.
.It Fl Fl debug
Print some extra information about the sorting process to the
standard output.
.It Fl Fl files0-from Ns = Ns Ar filename
Take the input file list from the file
.Ar filename .
The file names must be separated by NUL
(like the output produced by the command
.Dq find ... -print0 ) .
.It Fl Fl heapsort
Try to use heap sort, if the sort specifications allow.
This sort algorithm cannot be used with
.Fl u
and
.Fl s .
.It Fl Fl help
Print the help text and exit.
.It Fl H , Fl Fl mergesort
Use mergesort.
This is a universal algorithm that can always be used,
but it is not always the fastest.
.It Fl Fl mmap
Try to use file memory mapping system call.
It may increase speed in some cases.
.It Fl Fl qsort
Try to use quick sort, if the sort specifications allow.
This sort algorithm cannot be used with
.Fl u
and
.Fl s .
.It Fl Fl radixsort
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.
.It Fl Fl random-source Ns = Ns Ar filename
For random sort, the contents of
.Ar filename
are used as the source of the
.Sq seed
data for the hash function.
Two invocations of random sort with the same seed data
produce the same result if the input is also identical.
By default, the
.Xr arc4random_buf 3
function is used instead.
.It Fl Fl version
Print the version and exit.
.El
.Pp
A field is defined as a maximal sequence of characters other than the
field separator and record separator
.Pq newline by default .
Initial blank spaces are included in the field unless
.Fl 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
.Fl t
is specified).
For example, by default 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 field1 Ns Op , Ns Ar field2
option.
If
.Ar field2
is missing, the end of the key defaults to the end of the line.
.Pp
The arguments
.Ar field1
and
.Ar field2
have the form
.Em m.n
.Em (m,n > 0)
and can be followed by one or more of the modifiers
.Cm b , d , f , i ,
.Cm n , g , M
and
.Cm r ,
which correspond to the options discussed above.
When
.Cm b
is specified, it applies only to
.Ar field1
or
.Ar field2
where it is specified while the rest of the modifiers
apply to the whole key field regardless if they are
specified only with
.Ar field1
or
.Ar field2
or both.
A
.Ar field1
position specified by
.Em m.n
is interpreted as the
.Em n Ns th
character from the beginning of the
.Em m Ns th
field.
A missing
.Em \&.n
in
.Ar field1
means
.Ql \&.1 ,
indicating the first character of the
.Em m Ns th
field; if the
.Fl b
option is in effect,
.Em n
is counted from the first non-blank character in the
.Em m Ns th
field;
.Em m Ns \&.1b
refers to the first non-blank character in the
.Em m Ns th
field.
.No 1\&. Ns Em n
refers to the
.Em n Ns th
character from the beginning of the line;
if
.Em n
is greater than the length of the line, the field is taken to be empty.
.Pp
.Em n Ns th
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.
.Pp
A
.Ar field2
position specified by
.Em m.n
is interpreted as the
.Em n Ns th
character (including separators) from the beginning of the
.Em m Ns th
field.
A missing
.Em \&.n
indicates the last character of the
.Em m Ns th
field;
.Em m
= \&0
designates the end of a line.
Thus the option
.Fl k Ar v.x,w.y
is synonymous with the obsolete option
.Cm \(pl Ns Ar v-\&1.x-\&1
.Fl Ns Ar w-\&1.y ;
when
.Em y
is omitted,
.Fl k Ar v.x,w
is synonymous with
.Cm \(pl Ns Ar v-\&1.x-\&1
.Fl Ns Ar w\&.0 .
The obsolete
.Cm \(pl Ns Ar pos1
.Fl Ns Ar pos2
option is still supported, except for
.Fl Ns Ar w\&.0b ,
which has no
.Fl k
equivalent.
.Sh ENVIRONMENT
.Bl -tag -width Ds
.It Ev TMPDIR
Path to the directory in which temporary files will be stored.
Note that
.Ev TMPDIR
may be overridden by the
.Fl T
option.
.El
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /tmp/.bsdsort.PID.*
Temporary files.
.El
.Sh EXIT STATUS
The
.Nm
utility exits with one of the following values:
.Pp
.Bl -tag -width Ds -offset indent -compact
.It 0
Successfully sorted the input files or if used with
.Fl C
or
.Fl c ,
the input file already met the sorting criteria.
.It 1
On disorder (or non-uniqueness) with the
.Fl C
or
.Fl c
options.
.It 2
An error occurred.
.El
.Sh SEE ALSO
.Xr comm 1 ,
.Xr join 1 ,
.Xr uniq 1
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification, except that it ignores the user's
.Xr locale 1
and always assumes
.Ev LC_ALL Ns =C.
.Pp
The flags
.Op Fl gHhiMRSsTVz
are extensions to that specification.
.Pp
All long options are extensions to the specification.
Some are provided for compatibility with GNU
.Nm ,
others are specific to this implementation.
.Pp
Some implementations of
.Nm
honor the
.Fl b
option even when no key fields are specified.
This implementation follows historic practice and
.St -p1003.1-2008
in only honoring
.Fl b
when it precedes a key field.
.Pp
The historic practice of allowing the
.Fl o
option to appear after the
.Ar file
is supported for compatibility with older versions of
.Nm .
.Pp
The historic key notations
.Cm \(pl Ns Ar pos1
and
.Fl Ns Ar pos2
are supported for compatibility with older versions of
.Nm
but their use is highly discouraged.
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .
.Sh AUTHORS
.An Gabor Kovesdan Aq Mt gabor@FreeBSD.org
.An Oleg Moskalenko Aq Mt mom040267@gmail.com
.Sh CAVEATS
This implementation of
.Nm
has no limits on input line length (other than imposed by available
memory) or any restrictions on bytes allowed within lines.
.Pp
The performance depends highly on
efficient choice of sort keys and key complexity.
The fastest sort is on whole lines, with option
.Fl s .
For the key specification, the simpler to process the
lines the faster the search will be.
.Pp
When sorting by arithmetic value, using
.Fl n
results in much better performance than
.Fl g
so its use is encouraged whenever possible.