NAME

       join - join lines of two files on a common field

SYNOPSIS

       join [OPTION]... FILE1 FILE2

DESCRIPTION

       For  each  pair  of input lines with identical join fields, write a line to standard output.  The default
       join field is the first, delimited by whitespace.  When FILE1 or FILE2 (not both)  is  -,  read  standard
       input.

       -a FILENUM
              also  print unpairable lines from file FILENUM, where FILENUM is 1 or 2, corresponding to FILE1 or
              FILE2

       -e EMPTY
              replace missing input fields with EMPTY

       -i, --ignore-case
              ignore differences in case when comparing fields

       -j FIELD
              equivalent to '-1 FIELD -2 FIELD'

       -o FORMAT
              obey FORMAT while constructing output line

       -t CHAR
              use CHAR as input and output field separator

       -v FILENUM
              like -a FILENUM, but suppress joined output lines

       -1 FIELD
              join on this FIELD of file 1

       -2 FIELD
              join on this FIELD of file 2

       --check-order
              check that the input is correctly sorted, even if all input lines are pairable

       --nocheck-order
              do not check that the input is correctly sorted

       --header
              treat the first line in each file as field headers, print them without trying to pair them

       --help display this help and exit

       --version
              output version information and exit

       Unless -t CHAR is given, leading blanks separate fields and are ignored, else  fields  are  separated  by
       CHAR.   Any  FIELD  is  a  field  number  counted from 1.  FORMAT is one or more comma or blank separated
       specifications, each being 'FILENUM.FIELD' or '0'.  Default FORMAT outputs the join field, the  remaining
       fields  from  FILE1,  the  remaining  fields from FILE2, all separated by CHAR.  If FORMAT is the keyword
       'auto', then the first line of each file determines the number of fields output for each line.

       Important: FILE1 and FILE2 must be sorted on the join fields.  E.g., use "sort -k 1b,1" if 'join' has  no
       options,  or  use  "join -t ''" if 'sort' has no options.  Note, comparisons honor the rules specified by
       'LC_COLLATE'.  If the input is not sorted and some lines cannot be joined,  a  warning  message  will  be
       given.

AUTHOR

       Written by Mike Haertel.

REPORTING BUGS

       Report join bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report join translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright  ©  2013  Free  Software  Foundation,  Inc.   License  GPLv3+:  GNU  GPL  version  3  or  later
       <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to  the  extent
       permitted by law.

SEE ALSO

       comm(1), uniq(1)

       The  full  documentation  for  join is maintained as a Texinfo manual.  If the info and join programs are
       properly installed at your site, the command

              info coreutils 'join invocation'

       should give you access to the complete manual.