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diff --git a/doc/manual/nix-hash.xml b/doc/manual/nix-hash.xml new file mode 100644 index 000000000000..3a28fe4c6b64 --- /dev/null +++ b/doc/manual/nix-hash.xml @@ -0,0 +1,153 @@ +<refentry xmlns="http://docbook.org/ns/docbook" + xmlns:xlink="http://www.w3.org/1999/xlink"> + +<refnamediv> + <refname>nix-hash</refname> + <refpurpose>compute the cryptographic hash of a path</refpurpose> +</refnamediv> + +<refsynopsisdiv> + <cmdsynopsis> + <command>nix-hash</command> + <arg><option>--flat</option></arg> + <arg><option>--base32</option></arg> + <arg><option>--truncate</option></arg> + <arg><option>--type</option> <replaceable>hashAlgo</replaceable></arg> + <arg choice='plain' rep='repeat'><replaceable>path</replaceable></arg> + </cmdsynopsis> + <cmdsynopsis> + <command>nix-hash</command> + <arg choice='plain'><option>--to-base16</option></arg> + <arg choice='plain' rep='repeat'><replaceable>hash</replaceable></arg> + </cmdsynopsis> + <cmdsynopsis> + <command>nix-hash</command> + <arg choice='plain'><option>--to-base32</option></arg> + <arg choice='plain' rep='repeat'><replaceable>hash</replaceable></arg> + </cmdsynopsis> +</refsynopsisdiv> + + +<refsection><title>Description</title> + +<para>The command <command>nix-hash</command> computes the +cryptographic hash of the contents of each +<replaceable>path</replaceable> 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.</para> + +<para>The hash is computed over a <emphasis>serialisation</emphasis> +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 <emphasis>NAR format</emphasis> produced by +<command>nix-store</command> <option>--dump</option>. Thus, +<literal>nix-hash <replaceable>path</replaceable></literal> yields the +same cryptographic hash as <literal>nix-store --dump +<replaceable>path</replaceable> | md5sum</literal>.</para> + +</refsection> + + +<refsection><title>Options</title> + +<variablelist> + + <varlistentry><term><option>--flat</option></term> + + <listitem><para>Print the cryptographic hash of the contents of + each regular file <replaceable>path</replaceable>. That is, do + not compute the hash over the dump of + <replaceable>path</replaceable>. The result is identical to that + produced by the GNU commands <command>md5sum</command> and + <command>sha1sum</command>.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--base32</option></term> + + <listitem><para>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 + <function>fetchurl</function>).</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--truncate</option></term> + + <listitem><para>Truncate hashes longer than 160 bits (such as + SHA-256) to 160 bits.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--type</option> <replaceable>hashAlgo</replaceable></term> + + <listitem><para>Specify a cryptographic hash, which can be one of + <literal>md5</literal>, <literal>sha1</literal>, and + <literal>sha256</literal>.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--to-base16</option></term> + + <listitem><para>Don’t hash anything, but convert the base-32 hash + representation <replaceable>hash</replaceable> to + hexadecimal.</para></listitem> + + </varlistentry> + + <varlistentry><term><option>--to-base32</option></term> + + <listitem><para>Don’t hash anything, but convert the hexadecimal + hash representation <replaceable>hash</replaceable> to + base-32.</para></listitem> + + </varlistentry> + +</variablelist> + +</refsection> + + +<refsection><title>Examples</title> + +<para>Computing hashes: + +<screen> +$ mkdir test +$ echo "hello" > test/world + +$ nix-hash test/ <lineannotation>(MD5 hash; default)</lineannotation> +8179d3caeff1869b5ba1744e5a245c04 + +$ nix-store --dump test/ | md5sum <lineannotation>(for comparison)</lineannotation> +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</screen> + +</para> + +<para>Converting between hexadecimal and base-32: + +<screen> +$ nix-hash --type sha1 --to-base32 e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6 +nvd61k9nalji1zl9rrdfmsmvyyjqpzg4 + +$ nix-hash --type sha1 --to-base16 nvd61k9nalji1zl9rrdfmsmvyyjqpzg4 +e4fd8ba5f7bbeaea5ace89fe10255536cd60dab6</screen> + +</para> + +</refsection> + + +</refentry> |