---
name: "cksum"
section: "3tcl"
platform: "linux"
package: "tcllib"
version: "2.0+dfsg-4"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/cksum/3tcl"
---

# cksum(3tcl)

Calculate a cksum(1) compatible checksum

```

```

## NAME

cksum - Calculate a [cksum(1)](/cksum/1.md) compatible checksum

## SYNOPSIS

package require **Tcl 8.5 9**

package require **cksum ?1.1.5?**

**::crc::cksum** ?*-format format*? ?*-chunksize size*? \[ *-channel chan* \| *-filename file* \| *string* \]

**::crc::CksumInit**

**::crc::CksumUpdate** *token* *data*

**::crc::CksumFinal** *token*

```

```

## DESCRIPTION

This package provides a Tcl implementation of the [cksum(1)](/cksum/1.md) algorithm based upon information provided at in the GNU implementation of this program as part of the GNU Textutils 2.0 package.

## COMMANDS

- **::crc::cksum** ?*-format format*? ?*-chunksize size*? \[ *-channel chan* \| *-filename file* \| *string* \]

  The command takes string data or a channel or file name and returns a checksum value calculated using the **[cksum(1)](/cksum/1.md)** algorithm. The result is formatted using the [*format*(3tcl)](/format/3tcl.md) specifier provided or as an unsigned integer (%u) by default.

## OPTIONS

- \-channel *name*

  Return a checksum for the data read from a channel. The command will read data from the channel until the **eof** is true. If you need to be able to process events during this calculation see the **PROGRAMMING INTERFACE** section

- \-filename *name*

  This is a convenience option that opens the specified file, sets the encoding to binary and then acts as if the *-channel* option had been used. The file is closed on completion.

- \-format *string*

  Return the checksum using an alternative format template.

## PROGRAMMING INTERFACE

The cksum package implements the checksum using a context variable to which additional data can be added at any time. This is expecially useful in an event based environment such as a Tk application or a web server package. Data to be checksummed may be handled incrementally during a **fileevent** handler in discrete chunks. This can improve the interactive nature of a GUI application and can help to avoid excessive memory consumption.

- **::crc::CksumInit**

  Begins a new cksum context. Returns a token ID that must be used for the remaining functions. An optional seed may be specified if required.

- **::crc::CksumUpdate** *token* *data*

  Add data to the checksum identified by token. Calling *CksumUpdate $token "abcd"* is equivalent to calling *CksumUpdate $token "ab"* followed by *CksumUpdate $token "cb"*. See **EXAMPLES**.

- **::crc::CksumFinal** *token*

  Returns the checksum value and releases any resources held by this token. Once this command completes the token will be invalid. The result is a 32 bit integer value.

## EXAMPLES

```
% crc::cksum "Hello, World!"
2609532967
```

```
% crc::cksum -format 0x%X "Hello, World!"
0x9B8A5027
```

```
% crc::cksum -file cksum.tcl
1828321145
```

```
% set tok [crc::CksumInit]
% crc::CksumUpdate $tok "Hello, "
% crc::CksumUpdate $tok "World!"
% crc::CksumFinal $tok
2609532967
```

## AUTHORS

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

[crc32(3tcl)](/crc32/3tcl.md), [sum(3tcl)](/sum/3tcl.md)

## KEYWORDS

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

## CATEGORY

Hashes, checksums, and encryption

## COPYRIGHT

```
Copyright (c) 2002, Pat Thoyts
```