.\" Copyright (c) 1990 The Regents of the University of California.
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\" %sccs.include.redist.roff%
.\" @(#)join.1 6.9 (Berkeley) %G%
.Nd relational database operator
.Fl a Ar file_number | Fl v Ar file_number
.Op Fl j Ar file_number field
The join utility performs an ``equality join'' on the specified files
and writes the result to the standard output.
The ``join field'' is the field in each file by which the files are compared.
The first field in each line is used by default.
There is one line in the output for each pair of lines in
which have identical join fields.
Each output line consists of the join field, the remaining fields from
and then the remaining fields from
The default field separators are tab and space characters.
In this case, multiple tabs and spaces count as a single field separator,
and leading tabs and spaces are ignored.
The default output field separator is a single space character.
Many of the options use file and field numbers.
Both file numbers and field numbers are 1 based, i.e. the first file on
the command line is file number 1 and the first field is field number 1.
The following options are available:
In addition to the default output, produce a line for each unpairable
Replace empty output fields with
option specifies the fields that will be output from each file for
each line with matching join fields.
The elements of list must be either comma (``,'') or whitespace separated.
(The latter requires quoting to protect it from the shell, or, a simpler
approach is to use multiple
as a field delimiter for both input and output.
in a line is significant.
Do not display the default output, but display a line for each unpairable
may be specified at the same time.
When the default field delimiter characters are used, the files to be joined
should be ordered in the collating sequence of
option, on the fields on which they are to be joined, otherwise
may not report all field matches.
When the field delimiter characters are specified by the
option, the collating sequence should be the same as
is ``-'', the standard input is used.
utility exits 0 on success, and >0 if an error occurs.
For compatibility with historic versions of
the following options are available:
In addition to the default output, produce a line for each unpairable line
in both file 1 and file 2.
field of both file 1 and file 2.
Historical implementations of
permitted multiple arguments to the
These arguments were of the form ``file_number.field_number'' as described
This has obvious difficulties in the presence of files named ``1.2''.
These options are available only so historic shellscripts don't require
modification and should not be used.
command is expected to be
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