-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

--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