join - relational database operator
] file1 file2
forms, on the standard output, a join of the two relations specified
by the lines of file1
. If one of the file names is the
standard input is used.
must be sorted in increasing ASCII
collating sequence on the fields on which they are to be joined, normally the
first in each line.
There is one line in the output for each pair of lines in file1
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
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.
- 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
- Use character c as the only separator (tab character) on input and
output. Every appearance of c in a line is significant.
- sort /etc/passwd | join -t: -1 1 -a 1 -e "" - bdays
- Add birthdays to the /etc/passwd file, leaving unknown birthdays
empty. The layout of /adm/users is given in passwd(5);
bdays contains sorted lines like
- tr : ' ' </etc/passwd | 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.
With default field separation, the collating sequence is that of sort -b
, the sequence is that of
sort -tx -ky,y.
One of the files must be randomly accessible.