Name

       nix-hash - compute the cryptographic hash of a path

Synopsis

       nix-hash [--flat] [--base32] [--truncate] [--type hashAlgo] path…

       nix-hash --to-base16 hash…

       nix-hash --to-base32 hash…

Description

       The  command  nix-hash  computes  the  cryptographic hash of the contents of each path and
       prints it on standard output. By  default,  it  computes  an  MD5  hash,  but  other  hash
       algorithms are available as well. The hash is printed in hexadecimal. To generate the same
       hash as nix-prefetch-url you have to specify multiple arguments, see below for an example.

       The hash is computed over a serialisation of each path: a dump of  the  file  system  tree
       rooted  at  the path. This allows directories and symlinks to be hashed as well as regular
       files.  The  dump  is  in  the   NAR   format   produced   by   nix-store   --dump   (nix-
       store.md#operation---dump).   Thus,  nix-hash  path  yields the same cryptographic hash as
       nix-store --dump path | md5sum.

Options

       • --flat
         Print the cryptographic hash of the contents of each regular file path. That is, do  not
         compute the hash over the dump of path.  The result is identical to that produced by the
         GNU commands md5sum and sha1sum.

       • --base32
         Print the hash in a  base-32  representation  rather  than  hexadecimal.   This  base-32
         representation  is  more compact and can be used in Nix expressions (such as in calls to
         fetchurl).

       • --truncate
         Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.

       • --type hashAlgo
         Use the specified cryptographic hash algorithm, which can be one of md5,  sha1,  sha256,
         and sha512.

       • --to-base16
         Don’t hash anything, but convert the base-32 hash representation hash to hexadecimal.

       • --to-base32
         Don’t hash anything, but convert the hexadecimal hash representation hash to base-32.

Examples

       Computing the same hash as nix-prefetch-url:

       $ nix-prefetch-url file://<(echo test)
       1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
       $ nix-hash --type sha256 --flat --base32 <(echo test)
       1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj

       Computing hashes:

       $ mkdir test
       $ echo "hello" > test/world

       $ nix-hash test/ (MD5 hash; default)
       8179d3caeff1869b5ba1744e5a245c04

       $ nix-store --dump test/ | md5sum (for comparison)
       8179d3caeff1869b5ba1744e5a245c04  -

       $ nix-hash --type sha1 test/
       e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6

       $ nix-hash --type sha1 --base32 test/
       nvd61k9nalji1zl9rrdfmsmvyyjqpzg4

       $ nix-hash --type sha256 --flat test/
       error: reading file `test/': Is a directory

       $ nix-hash --type sha256 --flat test/world
       5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03

       Converting between hexadecimal and base-32:

       $ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
       nvd61k9nalji1zl9rrdfmsmvyyjqpzg4

       $ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
       e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6

                                                                                      nix-hash(1)