NAME

       join - relational database operator

SYNOPSIS

       join [ options ] file1 file2

DESCRIPTION

       Join  forms, on the standard output, a join of the two relations 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, normally 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.

EXAMPLES

       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.

SOURCE

       /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.

                                                                                     JOIN(1plan9)