sum (Unix)

sum is a core utility available on 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.[1]

Original author(s)Ken Thompson
Developer(s)AT&T Bell Laboratories
Initial releaseNovember 3, 1971; 49 years ago (1971-11-03)
Operating systemUnix, Unix-like, Inferno
Licensecoreutils: GPLv3+


There is a GNU utility written by Kayvan Aghaiepour and David MacKenzie and distributed with the Unix- and Linux-based operating systems.

According to the manual page,[1] sum uses two different algorithms for calculating the checksum and blocks, the SYSV checksum algorithm and the BSD checksum (default) algorithm. Switching between the two algorithms is done via command line options.

The algorithms implemented in this program are less sensitive than more modern checksum methods; the SYSV algorithm does not even depend on the order of the data. The GNU manual page states: "sum is provided for compatibility; the cksum program is preferable in new applications".


The sum utility is invoked from the command line according to the following syntax:

sum [OPTION]... [FILE]...

with the possible option parameters being:

  • -r
  • -s, --sysv
  • --help
    • display the help screen and exit
  • --version
    • output version information and exit

When no file parameter is given, or when FILE is -, the standard input is used as input file.

See alsoEdit


  1. ^ a b sum(1) — manual pages from GNU coreutils

External linksEdit