JOIN(1) INTERACTIVE UNIX System JOIN(1)
NAME
join - relational data base operator
SYNOPSIS
join [ options ] file1 file2
DESCRIPTION
The join command forms, on the standard output, a join of
the two relations specified by the lines of file1 and file2.
If file1 is -, the standard input is used.
File1 and file2 must be sorted in increasing ASCII collating
sequence on the fields on which they are to be joined, nor-
mally the first in each line [see sort(1)].
There is one line in the output for each pair of lines in
file1 and file2 that have identical join fields. The output
line normally consists of the common field, then the rest of
the line from file1, then the rest of the line from file2.
The default input field separators are blank, 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 blank.
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. The following options are recognized:
-an 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.
-jn m Join on the mth field of file n. If n is missing,
use the mth field in each file. Fields are num-
bered starting with 1.
-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.
-tc 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.
EXAMPLE
The following command line will join the password file and
the group file, matching on the numeric group ID, and
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JOIN(1) INTERACTIVE UNIX System JOIN(1)
outputting the login name, the group name, and the login
directory. It is assumed that the files have been sorted in
ASCII collating sequence on the group ID fields.
join -j1 4 -j2 3 -o 1.1 2.1 1.6 -t: /etc/passwd
/etc/group
SEE ALSO
awk(1), comm(1), sort(1), uniq(1).
BUGS
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(1) are
wildly incongruous.
File names that are numeric may cause conflict when the -o
option is used right before listing file names.
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