Name

       nix-hash - compute the cryptographic hash of a path

Synopsis

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

       nix-hash [--to-base16|--to-base32|--to-base64|--to-sri] [--type hashAlgo] 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.  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.

       •  --base16
          Print the hash in a hexadecimal representation (default).

       •  --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).

       •  --base64
          Similar  to  –base32,  but  print the hash in a base-64 representation, which is more compact than the
          base-32 one.

       •  --sri
          Print the hash in SRI format with base-64 encoding.  The type of hash algorithm will be  prepended  to
          the hash string, followed by a hyphen (-) and the base-64 hash body.

       •  --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.

       •  --to-base64
          Don’t hash anything, but convert the hexadecimal hash representation hash to base-64.

       •  --to-sri
          Don’t hash anything, but convert the hexadecimal hash representation hash to SRI.

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 --base16 test/
       e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6

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

       $ nix-hash --type sha1 --base64 test/
       5P2Lpfe76upazon+ECVVNs1g2rY=

       $ nix-hash --type sha1 --sri test/
       sha1-5P2Lpfe76upazon+ECVVNs1g2rY=

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

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

       Converting between hexadecimal, base-32, base-64, and SRI:

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

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

       $ nix-hash --type sha1 --to-base64 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
       5P2Lpfe76upazon+ECVVNs1g2rY=

       $ nix-hash --type sha1 --to-sri nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
       sha1-5P2Lpfe76upazon+ECVVNs1g2rY=

       $ nix-hash --to-base16 sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
       e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6

                                                                                                     nix-hash(1)