cksum

file checksum and byte count calculator

TLDR

Calculate checksum of file

$ cksum [file.txt]

Calculate checksum of multiple files

$ cksum [file1] [file2]

Calculate from stdin

$ echo "data" | cksum

Use SHA256 algorithm

$ cksum --algorithm sha256 [file.txt]

Verify checksums from file

$ cksum -c [checksums.txt]

Output in base64

$ cksum --base64 [file.txt]

cksum computes a cyclic redundancy check (CRC) checksum and byte count for each specified file, or for standard input if no file is given. It is part of GNU coreutils and is commonly used to verify file integrity after transfers or copies.By default, cksum uses the POSIX-standard 32-bit CRC algorithm. Modern versions of cksum (GNU coreutils 9.0+) support additional algorithms including MD5, SHA1, SHA256, and SHA512 via the --algorithm option, making it a versatile replacement for separate checksum utilities.The output format includes the checksum value, byte count, and filename. When using the --check option, cksum can read previously generated checksum files and verify that the listed files have not been modified.

PARAMETERS

-a, --algorithm name

Select algorithm (crc, md5, sha1, sha256, sha512, etc.)

-c, --check

Read checksums and verify them

-l, --length bits

Digest length in bits

--base64

Output base64-encoded digest

--raw

Output raw binary digest

--tag

BSD-style checksum (default)

--untagged

Reversed style without digest type

-z, --zero

End lines with NUL instead of newline

--ignore-missing

Don't fail for missing files during check

--quiet

Don't print OK for verified files

--status

Silent mode, exit code shows result

-w, --warn

Warn about malformed checksum lines

OUTPUT FORMAT

$ checksum byte_count filename

INSTALL

sudo apt install coreutils

sudo dnf install coreutils

sudo pacman -S coreutils

sudo apk add coreutils

sudo zypper install coreutils

brew install coreutils

nix profile install nixpkgs#coreutils

CAVEATS

CRC32 is not cryptographically secure. Use SHA256 or stronger for security-critical verification. Reads stdin when no file given or file is -.

HISTORY

cksum was standardized in POSIX.2 (1992). It is part of GNU coreutils. The --algorithm option for SHA/MD5 was added in GNU coreutils 9.0 (2021).