md5sum

Calculate MD5 hash of a file

$ md5sum [file]

$ md5sum [file1] [file2] [file3]

$ echo "text" | md5sum

$ md5sum [*.iso] > checksums.md5

$ md5sum -c checksums.md5

$ md5sum -c --quiet checksums.md5

$ md5sum -c --status checksums.md5

$ md5sum --tag [file]

md5sum [options] [file...]

md5sum computes and verifies MD5 message digests (checksums). MD5 produces a 128-bit hash value, typically displayed as a 32-character hexadecimal number.
The tool is commonly used to verify file integrity after transfers, detect changes in files, and generate unique identifiers for content. Files can be checked against a previously generated checksum file.
Note that MD5 is cryptographically broken and should not be used for security purposes. Use SHA-256 or better for security-critical applications.

-c, --check

Read checksums and verify files.

Don't print OK for verified files.

Don't output, use exit status only.

Warn about malformed checksum lines.

Exit non-zero for malformed lines.

Create BSD-style checksum output.

Read files in binary mode.

Read files in text mode (default).

Ignore missing files when checking.

MD5 is cryptographically broken and vulnerable to collision attacks. Not suitable for security purposes. Different results for binary vs text mode on some systems. Empty file produces constant hash d41d8cd98f00b204e9800998ecf8427e.

md5sum is part of GNU coreutils, implementing the MD5 algorithm designed by Ronald Rivest in 1991. MD5 was widely used for file verification until cryptographic weaknesses were demonstrated in 2004-2005. While still commonly used for non-security checksums, SHA-2 family hashes are recommended for security applications.

sha256sum(1), sha1sum(1), cksum(1), b2sum(1)