NAME

       combine - combine sets of lines from two files using boolean operations

SYNOPSIS

       combine file1 and file2

       combine file1 not file2

       combine file1 or file2

       combine file1 xor file2

       _ file1 and file2 _

       _ file1 not file2 _

       _ file1 or file2 _

       _ file1 xor file2 _

DESCRIPTION

       combine combines the lines in two files. Depending on the boolean operation specified, the
       contents will be combined in different ways:

       and Outputs lines that are in file1 if they are also present in file2.

       not Outputs lines that are in file1 but not in file2.

       or  Outputs lines that are in file1 or file2.

       xor Outputs lines that are in either file1 or file2, but not in both files.

       "-" can be specified for either file to read stdin for that file.

       The input files need not be sorted, and the lines are output in the order they occur in
       file1 (followed by the order they occur in file2 for the two "or" operations). Bear in
       mind that this means that the operations are not commutative; "a and b" will not
       necessarily be the same as "b and a". To obtain commutative behavior sort and uniq the
       result.

       Note that this program can be installed as "_" to allow for the syntactic sugar shown in
       the latter half of the synopsis (similar to the test/[ command). It is not currently
       installed as "_" by default, but you can alias it to that if you like.

SEE ALSO

       join(1)

AUTHOR

       Copyright 2006 by Joey Hess <joey@kitenet.net>

       Licensed under the GNU GPL.