JOIN(1) JOIN(1)
NAME
join - relational database operator
SYNOPSIS
join [ options ] file1 file2
DESCRIPTION
Join forms, on the standard output, a join of the two rela-
tions specified by the lines of file1 and file2. If one of
the file names 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.
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.
Input fields are normally separated spaces or tabs; output
fields by space. In this case, multiple separators count as
one, and leading separators are discarded.
The following options are recognized, with POSIX syntax.
-a n In addition to the normal output, produce a line for
each unpairable line in file n, where n is 1 or 2.
-v n Like -a, omitting output for paired lines.
-e s Replace empty output fields by string s.
-1 m
-2 m Join on the mth field of file1 or file2.
-jn m
Archaic equivalent for -n m.
-ofields
Each output line comprises the designated fields. The
comma-separated field designators are either 0, meaning
the join field, or have the form n.m, where n is a file
number and m is a field number. Archaic usage allows
separate arguments for field designators.
-tc Use character c as the only separator (tab character)
on input and output. Every appearance of c in a line
is significant.
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JOIN(1) JOIN(1)
EXAMPLES
sort /adm/users | join -t: -a 1 -e "" - bdays
Add birthdays to password information, leaving unknown
birthdays empty. The layout of is given in users(6);
bdays contains sorted lines like `ken:Feb 4, 1953'.
tr : ' ' </adm/users | sort -k 3 3 >temp
join -1 3 -2 3 -o 1.1,2.1 temp temp | awk '$1 < $2'
Print all pairs of users with identical userids.
SOURCE
/sys/src/cmd/join.c
SEE ALSO
sort(1), comm(1), awk(1)
BUGS
With default field separation, the collating sequence is
that of sort -b -ky,y; with -t, the sequence is that of sort
-tx -ky,y.
One of the files must be randomly accessible.
Page 2 Plan 9 (printed 12/21/24)