sha1sum

Calculate the SHA1 checksum of a file

$ sha1sum [path/to/file]

$ sha1sum [file1] [file2] [file3]

$ sha1sum [*.iso] > [checksums.sha1]

$ sha1sum -c [checksums.sha1]

$ sha1sum -c --quiet [checksums.sha1]

$ echo -n "[text]" | sha1sum

sha1sum [OPTION]... [FILE]...

sha1sum computes and verifies SHA1 (160-bit) message digests as described in FIPS-180-1. It generates a unique 40-character hexadecimal hash for file contents, useful for verifying file integrity and detecting modifications.
With no FILE argument or when FILE is -, sha1sum reads from standard input. Output format is: checksum, space, mode indicator (* for binary, space for text), and filename.
When checking with -c, input should be previous sha1sum output. Each line is verified and reported as OK or FAILED.

-b, --binary

Read in binary mode

Read checksums from FILEs and verify them

Read in text mode (default)

Create a BSD-style checksum output

End each output line with NUL instead of newline

Don't fail for missing files when checking

Don't print OK for each successfully verified file

Don't output anything; use exit status for result

Exit non-zero for improperly formatted checksum lines

Warn about improperly formatted checksum lines

SHA-1 is cryptographically broken and vulnerable to collision attacks. It should not be used for security-sensitive applications like digital signatures. For stronger security, use sha256sum or sha512sum instead.

sha1sum is part of GNU coreutils, written by Ulrich Drepper, Scott Miller, and David Madore. SHA-1 was designed by the NSA and published by NIST in 1995. Collision vulnerabilities were demonstrated in 2017, leading to deprecation for cryptographic purposes.

sha256sum(1), sha512sum(1), md5sum(1), cksum(1)