cmp
The cmp command compares two files, and if they differ, tells the
first byte and line number where they differ. Its arguments are as
follows:
cmp options... from-file [to-file]
The file name `-' is always the standard input. cmp also
uses the standard input if one file name is omitted.
An exit status of 0 means no differences were found, 1 means some differences were found, and 2 means trouble.
cmp.