sha256sum

TLDR

Calculate the SHA256 checksum of a file

$ sha256sum [file]

Calculate checksums for multiple files

$ sha256sum [file1] [file2]

Read from stdin and calculate checksum

$ echo "text" | sha256sum

Generate a checksum file for later verification

$ sha256sum [file1] [file2] > [checksums.sha256]

Verify files against a checksum file

$ sha256sum -c [checksums.sha256]

Verify silently (only show failures)

$ sha256sum -c --quiet [checksums.sha256]

SYNOPSIS

sha256sum [-bctwz] [--tag] [--strict] [FILE...]

sha256sum computes and verifies SHA-256 cryptographic hash values. SHA-256 (Secure Hash Algorithm 256-bit) is part of the SHA-2 family and produces a 256-bit (32-byte) hash value, typically rendered as a 64-character hexadecimal number.
The command is commonly used to verify file integrity and authenticity. Software distributors often provide SHA256 checksums alongside downloads, allowing users to verify that files were not corrupted during transfer or tampered with.
When checking files with -c, the input file should contain lines in the format produced by sha256sum: the hash, two spaces (or a space and asterisk for binary mode), and the filename.

PARAMETERS

-b, --binary

Read in binary mode

-c, --check

Read checksums from file and verify them

-t, --text

Read in text mode (default)

--tag

Create a BSD-style checksum output

-z, --zero

End each output line with NUL, not newline

--quiet

Don't print OK for each verified file

--status

Don't output anything, exit code shows success

-w, --warn

Warn about improperly formatted checksum lines

--strict

Exit non-zero for improperly formatted checksum lines

--ignore-missing

Don't fail for missing files during verification

--help

Display help information

--version

Display version information

CAVEATS

SHA-256 is not designed for password hashing; use bcrypt or argon2 for that purpose. While SHA-256 is cryptographically secure against collisions, identical files always produce identical hashes, making it unsuitable for detecting small modifications with any probability of missing them. On macOS, the equivalent command is shasum -a 256.

HISTORY

SHA-256 was designed by the NSA and published by NIST in 2001 as part of the SHA-2 family of hash functions. The sha256sum command was added to GNU Coreutils to provide a standard Unix utility for computing these hashes. It has become essential for software distribution verification, replacing MD5 and SHA-1 which have known weaknesses. SHA-256 is widely used in security applications, including Bitcoin's proof-of-work system.