sha1sum

is a computer program that calculates and verifies SHA-1 hashes. It is commonly used to verify the integrity of files. It (or a variant) is installed by default on most Linux distributions. Typically distributed alongside are , , and , which use a specific SHA-2 hash function and , which uses the BLAKE2 cryptographic hash function. The SHA-1 variants are proven vulnerable to collision attacks, and users should instead use, for example, a SHA-2 variant such as or the BLAKE2 variant to prevent tampering by an adversary. It is included in GNU Core Utilities, Busybox (excluding ), and Toybox (excluding ). Ports to a wide variety of systems are available, including Microsoft Windows.

is a computer program that calculates and verifies SHA-1 hashes. It is commonly used to verify the integrity of files. It (or a variant) is installed by default on most Linux distributions. Typically distributed alongside are , , and , which use a specific SHA-2 hash function and , which uses the BLAKE2 cryptographic hash function. The SHA-1 variants are proven vulnerable to collision attacks, and users should instead use, for example, a SHA-2 variant such as or the BLAKE2 variant to prevent tampering by an adversary. It is included in GNU Core Utilities, Busybox (excluding ), and Toybox (excluding ). Ports to a wide variety of systems are available, including Microsoft Windows. $ sha1sum filename [filename2] ... > SHA1SUM If distributing one file, the file extension may be appended to the filename e.g.: $ sha1sum --binary my-zip.tar.gz > my-zip.tar.gz.sha1 The output contains one line per file of the form " {hash} SPACE (ASTERISK|SPACE) [{directory} SLASH] {filename} ". (Note well, if the hash digest creation is performed in text mode instead of binary mode, then there will be two space characters instead of a single space character and an asterisk.) For example: $ sha1sum -b my-zip.tar.gz d5db29cd03a2ed055086cef9c31c252b4587d6d0 *my-zip.tar.gz $ sha1sum -b subdir/filename2 55086cef9c87d6d031cd5db29cd03a2ed0252b45 *subdir/filename2 To verify that a file was downloaded correctly or that it has not been tampered with: $ sha1sum -c SHA1SUM filename: OK filename2: OK $ sha1sum -c my-zip.tar.gz.sha1 my-zip.tar.gz: OK

Hash file trees

can only create checksums of one or multiple files inside a directory, but not of a directory tree, i.e. of subdirectories, sub-subdirectories, etc. and the files they contain. This is possible by using in combination with the find command with the option, or by piping the output from into xargs . can create checksums of a directory tree. To use with : $ find s_* -type f -exec sha1sum '{}' \; 65c23f142ff6bcfdddeccebc0e5e63c41c9c1721 s_1/file_s11 d3d59905cf5fc930cd4bf5b709d5ffdbaa9443b2 s_2/file_s21 5590e00ea904568199b86aee4b770fb1b5645ab8 s_a/file_02 Likewise, piping the output from into yields the same output: $ find s_* -type f | xargs sha1sum 65c23f142ff6bcfdddeccebc0e5e63c41c9c1721 s_1/file_s11 d3d59905cf5fc930cd4bf5b709d5ffdbaa9443b2 s_2/file_s21 5590e00ea904568199b86aee4b770fb1b5645ab8 s_a/file_02

References

FreeBSD Manual Pages md5 OpenBSD General Commands Manual md5

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