cmp command compares two files, and if they differ,
tells the first byte and line number where they differ or reports
that one file is a prefix of the other. Bytes and
lines are numbered starting with 1. The arguments of
are as follows:
cmp options… from-file [to-file [from-skip [to-skip]]]
The file name - is always the standard input.
also uses the standard input if one file name is omitted. The
from-skip and to-skip operands specify how many bytes to
ignore at the start of each file; they are equivalent to the
cmp outputs nothing if the two files have the
same contents. If the two files have bytes that differ,
reports the location of the first difference to standard output:
from-file to-file differ: char byte-number, line line-number
If one file is a prefix of the other,
cmp reports the
shorter file’s name to standard error, followed by a blank and extra
information about the shorter file:
cmp: EOF on shorter-file extra-info
The message formats can differ outside the POSIX locale. POSIX allows but does not require the EOF diagnostic’s file name to be followed by a blank and additional information.
An exit status of 0 means no differences were found, 1 means some differences were found, and 2 means trouble.