Admin: Created page with "'''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..."

2019-07-12T11:37:45Z

Created page with "'''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..."

New page

'''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 in most Unix-like operating systems.[citation needed] Variants include shasum (which permits SHA-1 through SHA-512 hash functions to be selected manually), sha224sum, sha256sum, sha384sum and sha512sum, which use a specific SHA-2 hash function, and sha3sum (which permits SHA-3 through SHA3-512, SHAKE, RawSHAKE and Keccak functions to be selected manually). Versions for Microsoft Windows also exist, and the ActivePerl distribution includes a perl implementation of shasum. On FreeBSD this utility is called sha512 and contains additional features.

The SHA-1 variants are proven vulnerable to collision attacks, and users should use for example a SHA-2 variant such as sha256sum instead to prevent tampering by an adversary.

It is included in GNU Core Utilities, Busybox and Toybox.

== Usage ==
Several [[Source Code Management|source code management]] systems, including [[Git (software)|Git]], [[Mercurial (software)|Mercurial]], [[Monotone (software)|Monotone]], and [[Fossil (software)|Fossil]], use the sha1sum of various types of content (file content, directory trees, ancestry information, etc.) to uniquely identify them.

== Examples ==
To create a file with an sha1 hash in it, if one is not provided:
<source lang="console">
$ sha1sum filename [filename2] ... > SHA1SUM
</source>

If distributing one file, ".sha1" may be appended to the filename e.g.:
<source lang="console">
$ sha1sum my-zip.tar.gz > my-zip.tar.gz.sha1
</source>

The output contains one line per file of the form "<code>{hash} SPACE ASTERISK [{directory} SLASH] {filename}</code>". For example:
<source lang="console">
$ sha1sum -b my-zip.tar.gz
d5db29cd03a2ed055086cef9c31c252b4587d6d0 *my-zip.tar.gz
$ sha1sum -b subdir/filename2
55086cef9c87d6d031cd5db29cd03a2ed0252b45 *subdir/filename2
</source>
To verify the file was downloaded correctly:
<source lang="console">
$ sha1sum -c SHA1SUM
filename: OK
filename2: OK
$ sha1sum -c my-zip.tar.gz.sha1
my-zip.tar.gz: OK
</source>

===Hash file trees===
sha1sum 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 sha1sum in combination with the commands <tt>find</tt> and <tt>xargs</tt> (and optionally with <tt>sort</tt> so that the files are sorted in the checksum file).

== See also ==
* <tt>[[cksum]]</tt>
* [[Comparison of file verification software]]

==Source==
[http://wikipedia.org/ http://wikipedia.org/]

[[Category:Cryptographic algorithms]]
[[Category:Software]]

Sha1sum - Revision history

Admin: Created page with "'''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..."