join - join lines of two files on a common field

SYNOPSIS

       join  [-a  1|2]  [-v  1|2]  [-e  empty-string]  [-o field-
       list...] [-t char] [-j[1|2] field] [-1 field]  [-2  field]
       file1 file2
       join {--help,--version}

DESCRIPTION

       This  manual page documents the GNU version of join.  join
       prints to the standard output a  line  for  each  pair  of
       input  lines,  one  each  from  file1 and file2, that have
       identical join fields.  Either filename (but not both) can
       be  `-',  meaning  the  standard  input.   file1 and file2
       should be already sorted in increasing order (not  numeri-
       cally)  on the join fields; unless the -t option is given,
       they should be sorted ignoring blanks at the start of  the
       line, as sort does when given the -b option.

       The  defaults  are:  the  join field is the first field in
       each line; fields in the input are  separated  by  one  or
       more  blanks,  with  leading  blanks  on the line ignored;
       fields in the output are separated by a space; each output
       line consists of the join field, the remaining fields from
       file1, then the remaining fields from file2.

   OPTIONS
       -a file-number
              Print a line for each unpairable line in file file-
              number  (either  1 or 2), in addition to the normal
              output.

       -e string
              Replace empty output fields (those that are missing
              in the input) with string.

       -1, -j1 field
              Join on field field (a positive integer) of file 1.

       -2, -j2 field
              Join on field field (a positive integer) of file 2.

       -j field
              Equivalent to -1 field -2 field.

       -o field-list...
              Construct  each output line according to the format
              in field-list.  Each element in field-list consists
              of  a  file number (either 1 or 2), a period, and a
              field number (a positive integer).  The elements in
              the list are separated by commas or blanks.  Multi-
              ple field-list arguments can be given after a  sin-

       -t char
              Use character char as the input  and  output  field
              separator.

       -v file-number
              Print a line for each unpairable line in file file-
              number (either 1 or 2), instead of the normal  out-
              put.

       In  addition,  when  GNU  join is invoked with exactly one
       argument, the following options are recognized:

       --help Print a usage message on standard output  and  exit
              successfully.

       --version
              Print  version  information on standard output then
              exit successfully.