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sum - Man Page

Calculate a sum(1) compatible checksum


package require Tcl  8.2

package require sum  ?1.1.2?

::crc::sum ?-bsd | -sysv? ?-format fmt? ?-chunksize size? [ -filename file | -channel chan | string ]


This package provides a Tcl-only implementation of the sum(1) command which calculates a 16 bit checksum value from the input data.  The BSD sum algorithm is used by default but the SysV algorithm is also available.


::crc::sum ?-bsd | -sysv? ?-format fmt? ?-chunksize size? [ -filename file | -channel chan | string ]

The command takes string data or a file name or a channel and returns a checksum value calculated using the sum(1) algorithm. The result is formatted using the format(n) specifier provided or as an unsigned integer (%u) by default.



The SysV algorithm is fairly naive. The byte values are summed and any overflow is discarded. The lowest 16 bits are returned as the checksum.  Input with the same content but different ordering will give the same result.


This algorithm is similar to the SysV version but includes a bit rotation step which provides a dependency on the order of the data values.

-filename name

Return a checksum for the file contents instead of for parameter data.

-channel chan

Return a checksum for the contents of the specified channel. The channel must be open for reading and should be configured for binary translation. The channel will no be closed on completion.

-chunksize size

Set the block size used when reading data from either files or channels. This value defaults to 4096.

-format string

Return the checksum using an alternative format template.


% crc::sum "Hello, World!"
% crc::sum -format 0x%X "Hello, World!"
% crc::sum -file sum.tcl


Pat Thoyts

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category crc of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.

See Also

cksum(n), crc32(n), sum(1)


checksum, cksum, crc, crc32, cyclic redundancy check, data integrity, security, sum


Hashes, checksums, and encryption

Referenced By

cksum(n), crc16(n), crc32(n).

1.1.2 tcllib Cyclic Redundancy Checks