.TH COMM 1 
.CT 1 files
.SH NAME
comm \- select or reject lines common to two sorted files
.SH SYNOPSIS
.B comm
[
.B -123
]
.I file1 file2
.SH DESCRIPTION
.I Comm
reads
.I file1
and
.I file2,
which are ordered in
.SM ASCII 
collating sequence,
and produces a three column output: lines only in
.IR file1 ;
lines only in
.IR file2 ;
and lines in both files.
The file name
.L -
means the standard input.
.PP
Flag
.LR 1 ,
.LR 2 ,
or
.LR 3
suppresses printing of the corresponding
column.
.SH EXAMPLES
.TP
.L
comm -12 file1 file2
Print lines common to two sorted files.
.TP
.L
deroff -w /mail/lib/names.last | tr a-z A-Z | sort -u >temp
.br
.ns
.TP
.L
spell temp | comm -13 - temp
Print names that are known both to
.IR mail (1)
and
.IR spell (1)
.SH "SEE ALSO"
.IR sort (1),
.IR cmp (1), 
.IR diff (1), 
.IR uniq (1)
