Usage: join [OPTION]... FILE1 FILE2

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        print unpairable lines coming 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
    --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.

Important: FILE1 and FILE2 must be sorted on the join fields.