Sum (Unix)

codice_1 is a legacy utility available on some Unix and Unix-like operating systems. This utility outputs the checksum of each argument file, as well as the number of blocks they take on disk.
Overview.
The program is generally only useful for historical interest. It is not part of POSIX. Two algorithms are typically available: a 16-bit BSD checksum and a 32-bit SYSV checksum. Both are weaker than the (already weak) CRC32 used by cksum.
The default algorithm on FreeBSD and GNU implementations is the weaker BSD checksum. Switching between the two algorithms is done via command line options.
Syntax.
The sum utility is invoked from the command line according to the following syntax:
 sum [OPTION]... [FILE]...
with the possible option parameters being:
When no file parameter is given, or when FILE is codice_7, the standard input is used as input file.