.\"
.\" Derived from join(1), Unix 32V:
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.TH JOIN 1 "2/5/05" "Heirloom Toolchest" "User Commands"
.SH NAME
join \- relational database operator
.SH SYNOPSIS
\fBjoin\fR [\fIoptions\fR] [\fIfile1\fR] [\fIfile2\fR]
.SH DESCRIPTION
.I Join
forms, on the standard output,
a join
of the two relations specified by the lines of
.I file1
and
.IR file2 .
If either
.I file1
or
.I file2
is `\-', the standard input is used.
.PP
.I File1
and 
.I file2
must be sorted in increasing current collating
sequence on the fields
on which they are to be joined,
normally the first in each line.
.PP
There is one line in the output 
for each pair of lines in 
.I file1 
and 
.I file2
that have identical join fields.
The output line normally consists of the common field,
then the rest of the line from 
.IR file1 ,
then the rest of the line from
.IR file2 .
.PP
Fields are normally separated by blank, tab or newline.
In this case, multiple separators count as one, and
leading separators are discarded.
.PP
These options are recognized:
.TP
.BI \-a n
In addition to the normal output,
produce a line for each unpairable line in file
.IR n ,
where
.I n
is 1 or 2.
.TP
.BI \-e \ s
Replace empty output fields by string
.IR s .
.TP
.BI \-j n\ m
Join on the
.IR m th
field of file
.IR n .
If
.I n
is missing, use the
.IR m th
field in each file.
.TP
.BI \-o \ list
Each output line comprises the fields specified in
.IR list ,
each element of which has the form
.IR n . m ,
where
.I n
is a file number and
.I m
is a field number;
or
.BR 0 ,
which specifies the join field.
The
.I list
may either consist of multiple arguments,
or of a single argument with elements separated by spaces or commas.
.TP
.BI \-t c
Use character
.I c
as a separator (tab character).
Every appearance of
.I c
in a line is significant.
.PP
The following options have been introduced by POSIX.2:
.TP
.BI \-v n
Suppress normal output
and produce a line for each unpairable line in file
.IR n ,
where
.I n
is 1 or 2.
.TP
\fB\-1\fI\ m\fR
Join on the
.IR m th
field of file
.IR 1 .
.TP
\fB\-2\fI\ m\fR
Join on the
.IR m th
field of file
.IR 2 .
.SH "ENVIRONMENT VARIABLES"
.TP
.BR LANG ", " LC_ALL
See
.IR locale (7).
.TP
.B LC_CTYPE
Determines the mapping of bytes to characters.
.TP
.B LC_COLLATE
Specifies the collation sequence.
.SH "SEE ALSO"
sort(1),
comm(1),
awk(1),
locale(7)
.SH NOTES
With default field separation,
the collating sequence is that of
.IR sort\ \-b ;
with
.BR \-t ,
the sequence is that of a plain sort.
.PP
The conventions of
.I join, sort, comm, uniq
and
.IR awk (1)
are wildly incongruous.