sum

sum computes a small, old-style checksum of a file and reports it along with the file's size in blocks.

sum [options] [file...]

$ sum archive.tar
12345 84 archive.tar

The output is the checksum, the block count, and the file name. With no file, sum reads standard input.

Which algorithm

sum predates the modern hashes and offers two historical algorithms:

Option	Algorithm
`-r`	The BSD checksum, counted in 1 KiB blocks. This is the default.
`-s`, `--sysv`	The System V checksum, counted in 512-byte blocks.

When to use it

sum exists for compatibility — for reading checksums produced by old tools, and for scripts that still expect its output. Its checksum is short and weak: it catches some accidental corruption, but it is easily fooled and gives no protection against tampering.

For anything new, do not use sum. Use a checksum command such as sha256sum, or cksum — both of which cksum can still produce, via cksum -a bsd and cksum -a sysv, if you need the legacy values.

Exit status

Code	Meaning
`0`	The checksum was computed.
`1`	A file could not be read.

Which algorithm #

When to use it #

Exit status #

See also

Which algorithm

When to use it

Exit status