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HP-UX 11i Version 3: February 2007

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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 a space.

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 for portability.

-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 is used as the field separator for both input and output.

-v file_number

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 with 1.

-2 f

Join on field f of file 2. Fields are numbered starting with 1.


Environment Variables

LC_COLLATE determines the collating sequence join expects from input files.

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 character.

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 sorted_file2:

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.


join: SVID2, SVID3, XPG2, XPG3, XPG4, POSIX.2

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