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1st chunk of `doc/manual/source/command-ref/nix-hash.md`
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# 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
*[Nix Archive (NAR)][Nix Archive] format* produced by [`nix-store
--dump`](@docroot@/command-ref/nix-store/dump.md).  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, instead of computing
  the hash of the [Nix Archive (NAR)](@docroot@/store/file-system-object/content-address.md#serial-nix-archive) of *path*,
  just [directly hash]((@docroot@/store/file-system-object/content-address.md#serial-flat) *path* as is.
  This requires *path* to resolve to a regular file rather than directory.
  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.
Title: nix-hash: Compute Cryptographic Hashes of Paths
Summary
The `nix-hash` command computes cryptographic hashes of files and directories. It serializes each path into a Nix Archive (NAR) format and then calculates the hash. Options allow specifying the hash algorithm, output format (hexadecimal, base32, base64, SRI), and whether to hash the file content directly (for regular files) instead of the NAR representation.