join - relational database operator
join [options] file1 file2
join forms, on the standard output, a join of the two relations
specified by the lines of file1 and file2. If file1 or file2 is -,
the standard input is used.
file1 and file2 must be sorted in increasing collating sequence (see
Environment Variables below) on the fields on which they are to be
joined; normally the first in each line.
The output contains one line for each pair of lines in file1 and file2
that have identical join fields. The output line normally consists of
the common field followed by the rest of the line from file1, then the
rest of the line from file2.
The default input field separators are space, tab, or new-line. In
this case, multiple separators count as one field separator, and
leading separators are ignored. The default output field separator is
Some of the below options use the argument n. This argument should be
a 1 or a 2 referring to either file1 or file2, respectively.
-a n In addition to the normal output, produce a line for each
unpairable line in file n, where n is 1 or 2.
-e s Replace empty output fields by string s.
-j m Join on field m of both files. The argument m must be
delimited by space characters. This option and the
following two are provided for backward compatibility.
Use of the -1 and -2 options ( see below ) is recommended
-j1 m Join on field m of file1.
-j2 m Join on field m of file2.
-o list Each output line comprises the fields specified in list,
each element of which has the form n.m, where n is a file
number and m is a field number. The common field is not
printed unless specifically requested.
-t c Use character c as a separator (tab character). Every
appearance of c in a line is significant. The character c
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is used as the field separator for both input and output.
Instead of the default output, produce a line only for
each unpairable line in file_number, where file_number is
1 or 2.
-1 f Join on field f of file 1. Fields are numbered starting
-2 f Join on field f of file 2. Fields are numbered starting
LC_COLLATE determines the collating sequence join expects from input
LC_CTYPE determines the alternative blank character as an input field
separator, and the interpretation of data within files as single
and/or multi-byte characters. LC_CTYPE also determines whether the
separator defined through the -t option is a single- or multi-byte
If LC_COLLATE or LC_CTYPE is not specified in the environment or is
set to the empty string, the value of LANG is used as a default for
each unspecified or empty variable. If LANG is not specified or is
set to the empty string, a default of ``C'' (see lang(5)) is used
instead of LANG. If any internationalization variable contains an
invalid setting, join behaves as if all internationalization variables
are set to ``C'' (see environ(5)).
International Code Set Support
Single- and multi-byte character code sets are supported with the
exception that multi-byte-character file names are not supported.
The following command line joins the password file and the group file,
matching on the numeric group ID, and outputting the login name, the
group name, and the login directory. It is assumed that the files
have been sorted in the collating sequence defined by the LC_COLLATE
or LANG environment variable on the group ID fields.
join -1 4 -2 3 -o 1.1 2.1 1.6 -t: /etc/passwd /etc/group
The following command produces an output consisting all possible
combinations of lines that have identical first fields in the two
sorted files sf1 and sf2, with each line consisting of the first and
third fields from sorted_file1 and the second and fourth fields from
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join -j1 1 -j2 1 -o 1.1,2.2,1.3,2.4 sorted_file1 sorted_file2
With default field separation, the collating sequence is that of sort
-b; with -t, the sequence is that of a plain sort.
The conventions of join, sort, comm, uniq, and awk are incongruous.
Numeric filenames may cause conflict when the -o option is used
immediately before listing filenames.
join was developed by OSF and HP.
awk(1), comm(1), sort(1), uniq(1).
join: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2
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