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This is needed to avoid this https://github.com/mesonbuild/meson/issues/13774 when we go back to making our subproject directory `src`.
154 lines
4.5 KiB
Markdown
154 lines
4.5 KiB
Markdown
# Name
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`nix-hash` - compute the cryptographic hash of a path
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# Synopsis
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`nix-hash` [`--flat`] [`--base32`] [`--truncate`] [`--type` *hashAlgo*] *path…*
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`nix-hash` [`--to-base16`|`--to-base32`|`--to-base64`|`--to-sri`] [`--type` *hashAlgo*] *hash…*
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# Description
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The command `nix-hash` computes the cryptographic hash of the contents
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of each *path* and prints it on standard output. By default, it computes
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an MD5 hash, but other hash algorithms are available as well. The hash
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is printed in hexadecimal. To generate the same hash as
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`nix-prefetch-url` you have to specify multiple arguments, see below for
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an example.
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The hash is computed over a *serialisation* of each path: a dump of
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the file system tree rooted at the path. This allows directories and
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symlinks to be hashed as well as regular files. The dump is in the
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*[Nix Archive (NAR)][Nix Archive] format* produced by [`nix-store
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--dump`](@docroot@/command-ref/nix-store/dump.md). Thus, `nix-hash path`
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yields the same cryptographic hash as `nix-store --dump path |
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md5sum`.
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[Nix Archive]: @docroot@/store/file-system-object/content-address.md#serial-nix-archive
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# Options
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- `--flat`
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Print the cryptographic hash of the contents of each regular file *path*.
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That is, instead of computing
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the hash of the [Nix Archive (NAR)](@docroot@/store/file-system-object/content-address.md#serial-nix-archive) of *path*,
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just [directly hash]((@docroot@/store/file-system-object/content-address.md#serial-flat) *path* as is.
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This requires *path* to resolve to a regular file rather than directory.
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The result is identical to that produced by the GNU commands
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`md5sum` and `sha1sum`.
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- `--base16`
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Print the hash in a hexadecimal representation (default).
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- `--base32`
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Print the hash in a base-32 representation rather than hexadecimal.
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This base-32 representation is more compact and can be used in Nix
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expressions (such as in calls to `fetchurl`).
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- `--base64`
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Similar to --base32, but print the hash in a base-64 representation,
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which is more compact than the base-32 one.
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- `--sri`
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Print the hash in SRI format with base-64 encoding.
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The type of hash algorithm will be prepended to the hash string,
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followed by a hyphen (-) and the base-64 hash body.
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- `--truncate`
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Truncate hashes longer than 160 bits (such as SHA-256) to 160 bits.
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- `--type` *hashAlgo*
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Use the specified cryptographic hash algorithm, which can be one of
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`md5`, `sha1`, `sha256`, and `sha512`.
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- `--to-base16`
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Don’t hash anything, but convert the base-32 hash representation
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*hash* to hexadecimal.
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- `--to-base32`
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Don’t hash anything, but convert the hexadecimal hash representation
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*hash* to base-32.
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- `--to-base64`
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Don’t hash anything, but convert the hexadecimal hash representation
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*hash* to base-64.
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- `--to-sri`
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Don’t hash anything, but convert the hexadecimal hash representation
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*hash* to SRI.
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# Examples
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Computing the same hash as `nix-prefetch-url`:
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```console
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$ nix-prefetch-url file://<(echo test)
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1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
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$ nix-hash --type sha256 --flat --base32 <(echo test)
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1lkgqb6fclns49861dwk9rzb6xnfkxbpws74mxnx01z9qyv1pjpj
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```
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Computing hashes:
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```console
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$ mkdir test
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$ echo "hello" > test/world
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$ nix-hash test/ (MD5 hash; default)
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8179d3caeff1869b5ba1744e5a245c04
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$ nix-store --dump test/ | md5sum (for comparison)
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8179d3caeff1869b5ba1744e5a245c04 -
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$ nix-hash --type sha1 test/
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e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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$ nix-hash --type sha1 --base16 test/
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e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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$ nix-hash --type sha1 --base32 test/
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nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
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$ nix-hash --type sha1 --base64 test/
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5P2Lpfe76upazon+ECVVNs1g2rY=
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$ nix-hash --type sha1 --sri test/
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sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
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$ nix-hash --type sha256 --flat test/
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error: reading file `test/': Is a directory
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$ nix-hash --type sha256 --flat test/world
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5891b5b522d5df086d0ff0b110fbd9d21bb4fc7163af34d08286a2e846f6be03
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```
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Converting between hexadecimal, base-32, base-64, and SRI:
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```console
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$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
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$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
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e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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$ nix-hash --type sha1 --to-base64 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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5P2Lpfe76upazon+ECVVNs1g2rY=
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$ nix-hash --type sha1 --to-sri nvd61k9nalji1zl9rrdfmsmvyyjqpzg4
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sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
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$ nix-hash --to-base16 sha1-5P2Lpfe76upazon+ECVVNs1g2rY=
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e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6
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```
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