Operating system | Unix, Unix-like |
---|---|
Platform | Cross-platform |
Type | Command |
cksum
is a
command in
Unix and
Unix-like
operating systems that generates a
checksum value for a file or stream of data. The cksum command reads each file given in its arguments, or
standard input if no arguments are provided, and outputs the file's 32-bit
cyclic redundancy check (CRC) checksum and
byte count.
[1] The CRC output by cksum is different from the CRC-32 used in zip, PNG and zlib.
[2]
The cksum
command can be used to verify that files transferred by unreliable means arrived intact.
[1] However, the CRC checksum calculated by the cksum
command is not
cryptographically secure: While it guards against accidental corruption (it is unlikely that the corrupted data will have the same checksum as the intended data), it is not difficult for an attacker to deliberately corrupt the file in a specific way that its checksum is unchanged. Unix-like systems typically include other commands for cryptographically secure checksums, such as
sha256sum.
The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. [3]
Latest GNU Coreutils cksum provides additional checksum algorithms via -a option, as an extension beyond POSIX. [1]
The standard cksum
command, as found on most Unix and Unix-like operating systems (including
Linux,
*BSD,
[4]
[5]
[6]
macOS, and
Solaris
[7]) uses a CRC algorithm based on the
ethernet standard frame check
[8] and is therefore interoperable between implementations. This is in contrast to the
sum command, which is not as interoperable and not compatible with the CRC-32 calculation. On
Tru64 operating systems, the cksum
command returns a different CRC value, unless the
environment variable CMD_ENV
is set to xpg4
.[
citation needed]
cksum
uses the
generator polynomial 0x04C11DB7 and appends to the message its length in
little endian representation. That length has
null bytes trimmed on the right end.
[8]
cksum FILE...
cksum OPTION
$ cksum test.txt
4038471504 75 test.txt
where 4038471504
represents the checksum value and 75
represents the file size of test.txt
.
Operating system | Unix, Unix-like |
---|---|
Platform | Cross-platform |
Type | Command |
cksum
is a
command in
Unix and
Unix-like
operating systems that generates a
checksum value for a file or stream of data. The cksum command reads each file given in its arguments, or
standard input if no arguments are provided, and outputs the file's 32-bit
cyclic redundancy check (CRC) checksum and
byte count.
[1] The CRC output by cksum is different from the CRC-32 used in zip, PNG and zlib.
[2]
The cksum
command can be used to verify that files transferred by unreliable means arrived intact.
[1] However, the CRC checksum calculated by the cksum
command is not
cryptographically secure: While it guards against accidental corruption (it is unlikely that the corrupted data will have the same checksum as the intended data), it is not difficult for an attacker to deliberately corrupt the file in a specific way that its checksum is unchanged. Unix-like systems typically include other commands for cryptographically secure checksums, such as
sha256sum.
The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. [3]
Latest GNU Coreutils cksum provides additional checksum algorithms via -a option, as an extension beyond POSIX. [1]
The standard cksum
command, as found on most Unix and Unix-like operating systems (including
Linux,
*BSD,
[4]
[5]
[6]
macOS, and
Solaris
[7]) uses a CRC algorithm based on the
ethernet standard frame check
[8] and is therefore interoperable between implementations. This is in contrast to the
sum command, which is not as interoperable and not compatible with the CRC-32 calculation. On
Tru64 operating systems, the cksum
command returns a different CRC value, unless the
environment variable CMD_ENV
is set to xpg4
.[
citation needed]
cksum
uses the
generator polynomial 0x04C11DB7 and appends to the message its length in
little endian representation. That length has
null bytes trimmed on the right end.
[8]
cksum FILE...
cksum OPTION
$ cksum test.txt
4038471504 75 test.txt
where 4038471504
represents the checksum value and 75
represents the file size of test.txt
.