cksum - Calculate and display checksums and byte counts

Format

cksum [-ciprtT] [file ... file ...]

Description

cksum calculates and displays a checksum for each input file. A checksum is an error-checking technique used by many programs as a quick way to compare files that have been moved from one location to another to ensure that no data has been lost. It also displays the number of 8-bit bytes in each file.

If you do not specify any files on the command line, or if you specify - as the file name, cksum reads the standard input.

When _UNIX03 is YES, the cksum output has the space-separated form: 
checksum bytecount filename
When _UNIX03 is unset or not YES, the cksum output has the tab-separated form: 
checksum     bytecount     filename

If the file operand is not specified, the path name and its leading white space is omitted.

Read error messages are controlled by the _UNIX03 variable.
  • If cksum fails with a read error and _UNIX03 is YES, it sends a diagnostic message to standard error, and does not show a checksum for that file.
  • If _UNIX03 is unset or not YES, cksum displays the checksum up to that point and marks the output line with FSUM6199 [read error].
cksum continues processing files in either case.

All other error messages are sent to standard error.

Options

cksum can calculate checksums in a variety of ways. The default is compatible with the POSIX standard. You can specify other algorithms with the following options. The POSIX standard does not recognize these algorithms; they are provided for compatibility with the UNIX sum command.
-c
Uses a standard 16-bit cyclic redundancy check (CRC-16).
-i
Uses the CCITT standard cyclic redundancy check (CRC-CCITT). Data communication network protocols often use a cyclic redundancy check to ensure proper transmission. This algorithm is more likely to produce a different sum for inputs; the only difference is byte order.
-p
Uses the POSIX checksum algorithm. This is the default.
-r
Enables the use of an alternate checksum algorithm that has the advantage of being sensitive to byte order.
-t
Produces a line containing the total number of bytes of data read as well as the checksum of the concatenation of the input files.
-T
Enables the automatic conversion of tagged files.

Localization

cksum uses the following localization environment variables:
  • LANG
  • LC_ALL
  • LC_CTYPE
  • LC_MESSAGES
  • LC_TYPE
  • NLSPATH

Environment variables

  • _UNIX03

For more information about the effect of _UNIX03 on the cksum command, see Shell commands changed for UNIX03.

Exit values

0
Successful completion.
1
Failure due to any of the following reasons:
  • Inability to open input file.
  • An error reading the input file.
  • Error turning off the automatic conversion of the input file.
2
Unknown command-line option.

Portability

POSIX.2, X/Open Portability Guide.

All the listed options are extensions of the POSIX standard.

Related information

cmp, diff, ls, sum, wc