.TH SORT 1plan9 
.SH NAME
sort \- sort and/or merge files
.SH SYNOPSIS
.B sort
[
.BI -cmuMbdf\&inrwt x
]
[
.BI + pos1
[
.BI - pos2
] ...
] ...
[
.B -k
.I pos1
[
.I ,pos2
]
] ...
.br
\h'0.5in'
[
.B -o
.I output
]
[
.B -T
.I dir
\&...
]
[
.I option
\&...
]
[
.I file
\&...
]
.SH DESCRIPTION
.I Sort\^
sorts
lines of all the
.I files
together and writes the result on
the standard output.
If no input files are named, the standard input is sorted.
.PP
The default sort key is an entire line.
Default ordering is
lexicographic by runes.
The ordering is affected globally by the following options,
one or more of which may appear.
.TP
.B -M
Compare as months.
The first three
non-white space characters
of the field
are folded
to upper case
and compared
so that
.L JAN
precedes
.LR FEB ,
etc.
Invalid fields
compare low to
.LR JAN .
.TP
.B -b
Ignore leading white space (spaces and tabs) in field comparisons.
.TP
.B -d
`Phone directory' order:
only letters,
accented letters,
digits and white space
are significant in comparisons.
.TP
.B -f
Fold lower case
letters onto upper case.
Accented characters are folded to their
non-accented upper case form.
.TP
.B -i
Ignore characters outside the
.SM ASCII
range 040-0176
in non-numeric comparisons.
.TP
.B -w
Like
.BR -i ,
but ignore only tabs and spaces.
.TP
.B -n
An initial numeric string,
consisting of optional white space,
optional plus or minus sign,
and zero or more digits with optional decimal point,
is sorted by arithmetic value.
.TP
.B -g
Numbers, like
.B -n 
but with optional 
.BR e -style
exponents, are sorted by value.
.TP
.B -r
Reverse the sense of comparisons.
.TP
.BI -t x\^
`Tab character' separating fields is
.IR x .
.PP
The notation
.BI + "pos1\| " - pos2\^
restricts a sort key to a field beginning at
.I pos1\^
and ending just before
.IR pos2 .
.I Pos1\^
and
.I pos2\^
each have the form
.IB m . n\f1,
optionally followed by one or more of the flags
.BR Mbdfginr ,
where
.I m\^
tells a number of fields to skip from the beginning of the line and
.I n\^
tells a number of characters to skip further.
If any flags are present they override all the global
ordering options for this key.
A missing
.BI \&. n\^
means
.BR \&.0 ;
a missing
.BI - pos2\^
means the end of the line.
Under the
.BI -t x\^
option, fields are strings separated by
.IR x ;
otherwise fields are
non-empty strings separated by white space.
White space before a field
is part of the field, except under option
.BR -b .
A
.B b
flag may be attached independently to
.IR pos1
and
.IR pos2.
.PP
The notation
.B -k
.IR pos1 [, pos2 ]
is how POSIX
.I sort
defines fields:
.I pos1
and
.I pos2
have the same format but different meanings.
The value of
.I  m\^
is origin 1 instead of origin 0
and a missing
.BI \&. n\^
in
.I pos2
is the end of the field.
.PP
When there are multiple sort keys, later keys
are compared only after all earlier keys
compare equal.
Lines that otherwise compare equal are ordered
with all bytes significant.
.PP
These option arguments are also understood:
.TP \w'\fL-z\fIrecsize\fLXX'u
.B -c
Check that the single input file is sorted according to the ordering rules;
give no output unless the file is out of sort.
.TP
.B -m
Merge; assume the input files are already sorted.
.TP
.B -u
Suppress all but one in each
set of equal lines.
Ignored bytes
and bytes outside keys
do not participate in
this comparison.
.TP
.B -o
The next argument is the name of an output file
to use instead of the standard output.
This file may be the same as one of the inputs.
.TP
.BI -T dir
Put temporary files in
.I dir
rather than in
.BR /var/tmp .
.ne 4
.SH EXAMPLES
.TP
.L sort -u +0f +0 list
Print in alphabetical order all the unique spellings
in a list of words
where capitalized words differ from uncapitalized.
.TP
.L sort -t: +1 /adm/users
Print the users file
sorted by user name
(the second colon-separated field).
.TP
.L sort -umM dates
Print the first instance of each month in an already sorted file.
Options
.B -um
with just one input file make the choice of a
unique representative from a set of equal lines predictable.
.TP
.L
grep -n '^' input | sort -t: +1f +0n | sed 's/[0-9]*://'
A stable sort: input lines that compare equal will 
come out in their original order.
.SH FILES
.BI /var/tmp/sort. <pid>.<ordinal>
.SH SOURCE
.B \*9/src/cmd/sort.c
.SH SEE ALSO
.IR uniq (1),
.IR look (1)
.SH DIAGNOSTICS
.I Sort
comments and exits with non-null status for various trouble
conditions and for disorder discovered under option
.BR -c .
.SH BUGS
An external null character can be confused
with an internally generated end-of-field character.
The result can make a sub-field not sort
less than a longer field.
.PP
Some of the options, e.g.
.B -i
and
.BR -M ,
are hopelessly provincial.