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)