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 blanks.

       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

       -z, --zero-terminated
              line delimiter is NUL, not newline

       --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

       GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
       Report any translation bugs to <https://translationproject.org/team/>

COPYRIGHT

       Copyright © 2020 Free Software Foundation, Inc.  License GPLv3+:  GNU  GPL  version  3  or
       later <https://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)

       Full documentation <https://www.gnu.org/software/coreutils/join>
       or available locally via: info '(coreutils) join invocation'