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 (stdin).

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 (stderr).

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 POSIXchecksum 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 autoconversion of tagged files.

Localization

cksum uses the following localization environment variables:

LANG
LC_ALL
LC_CTYPE
LC_MESSAGES
LC_TYPE
NLSPATH

See Localization for more information.

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:

Inability to open input file
An error reading the input file
Error turning off the autoconversion 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