join - join lines of two files on a common field

       Written by Mike Haertel.

       Copyright  ©  2024  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.

       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 STRING
              replace  missing  (empty)  input  fields  with STRING; I.e., missing fields specified with '-12jo'
              options

       -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.  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.

       join - join lines of two files on a common field

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

comm(1), uniq(1)

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

GNU coreutils 9.5                                  April 2025                                            JOIN(1)

join [OPTION]... FILE1FILE2