6.2 sum: Print checksum and block counts

sum computes a 16-bit checksum for each given file, or standard input if none are given or for a file of ‘-’. Synopsis:

sum [option]… [file]…

sum prints the checksum for each file followed by the number of blocks in the file (rounded up). If at least one file is given, file names are also printed.

By default, GNU sum computes checksums using an algorithm compatible with BSD sum and prints file sizes in units of 1024-byte blocks.

The program accepts the following options. Also see Common options.


Use the default (BSD compatible) algorithm. This option is included for compatibility with the System V sum. Unless -s was also given, it has no effect.


Compute checksums using an algorithm compatible with System V sum’s default, and print file sizes in units of 512-byte blocks.

sum is provided for compatibility; the cksum program (see next section) is preferable in new applications.

An exit status of zero indicates success, and a nonzero value indicates failure.