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6.3 cksum: Print and verify file checksums

cksum by default computes a cyclic redundancy check (CRC) checksum for each given file, or standard input if none are given or for a file of ‘-’.

cksum also supports the -a,--algorithm option to select the digest algorithm to use. cksum is the preferred interface to these digests, subsuming the other standalone checksumming utilities, which can be emulated using cksum -a md5 --untagged "$@" etc. Synopsis:

cksum [option]… [file]…

cksum is typically used to ensure that files have not been corrupted, by comparing the cksum output for the received files with the cksum output for the original files (typically given in the distribution).

cksum by default prints the POSIX standard CRC checksum for each file along with the number of bytes in the file, and the file name unless no arguments were given.

The same usage and options as the b2sum command are supported. See b2sum invocation. In addition cksum supports the following options.


Compute checksums using the specified digest algorithm.

Supported legacy checksums (which are not supported by --check):

sysv’      equivalent to sum -sbsd’       equivalent to sum -rcrc’       equivalent to cksum (the default)

Supported more modern digest algorithms are:

md5’       equivalent to md5sumsha1’      equivalent to sha1sumsha224’    equivalent to sha224sumsha256’    equivalent to sha256sumsha384’    equivalent to sha384sumsha512’    equivalent to sha512sumblake2b’   equivalent to b2sumsm3’       only available through cksum

Output extra information to stderr, like the checksum implementation being used.


Output using the original coreutils format used by the other standalone checksum utilities like md5sum for example. This format has the checksum at the start of the line, and may be more amenable to further processing by other utilities, especially in combination with the --zero option. Note this does not identify the digest algorithm used for the checksum. See md5sum invocation for details of this format.

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