mirror of
https://github.com/NixOS/nix
synced 2025-07-07 10:11:47 +02:00
<replaceable> -> <emphasis>
Pandoc doesn't know <replaceable> so let's force it to be rendered as italics.
This commit is contained in:
Eelco Dolstra
parent
ee05108472
commit
802150f987
76 changed files with 1029 additions and 1020 deletions
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@ -9,42 +9,42 @@ scope. Instead, you can access them through the `builtins` built-in
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value, which is a set that contains all built-in functions and values.
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For instance, `derivation` is also available as `builtins.derivation`.
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- `abort` s; `builtins.abort` s
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Abort Nix expression evaluation, print error message s.
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- `abort` *s*; `builtins.abort` *s*
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Abort Nix expression evaluation, print error message *s*.
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- `builtins.add` e1 e2
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Return the sum of the numbers e1 and e2.
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- `builtins.add` *e1* *e2*
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Return the sum of the numbers *e1* and *e2*.
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- `builtins.all` pred list
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Return `true` if the function pred returns `true` for all elements
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of list, and `false` otherwise.
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- `builtins.all` *pred* *list*
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Return `true` if the function *pred* returns `true` for all elements
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of *list*, and `false` otherwise.
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- `builtins.any` pred list
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Return `true` if the function pred returns `true` for at least one
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element of list, and `false` otherwise.
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- `builtins.any` *pred* *list*
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Return `true` if the function *pred* returns `true` for at least one
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element of *list*, and `false` otherwise.
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- `builtins.attrNames` set
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Return the names of the attributes in the set set in an
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- `builtins.attrNames` *set*
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Return the names of the attributes in the set *set* in an
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alphabetically sorted list. For instance, `builtins.attrNames { y
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= 1; x = "foo"; }` evaluates to `[ "x" "y" ]`.
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- `builtins.attrValues` set
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Return the values of the attributes in the set set in the order
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- `builtins.attrValues` *set*
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Return the values of the attributes in the set *set* in the order
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corresponding to the sorted attribute names.
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- `baseNameOf` s
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Return the *base name* of the string s, that is, everything
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- `baseNameOf` *s*
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Return the *base name* of the string *s*, that is, everything
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following the final slash in the string. This is similar to the GNU
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`basename` command.
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- `builtins.bitAnd` e1 e2
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Return the bitwise AND of the integers e1 and e2.
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- `builtins.bitAnd` *e1* *e2*
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Return the bitwise AND of the integers *e1* and *e2*.
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- `builtins.bitOr` e1 e2
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Return the bitwise OR of the integers e1 and e2.
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- `builtins.bitOr` *e1* *e2*
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Return the bitwise OR of the integers *e1* and *e2*.
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- `builtins.bitXor` e1 e2
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Return the bitwise XOR of the integers e1 and e2.
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- `builtins.bitXor` *e1* *e2*
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Return the bitwise XOR of the integers *e1* and *e2*.
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- `builtins`
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The set `builtins` contains all the built-in functions and values.
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@ -56,17 +56,17 @@ For instance, `derivation` is also available as `builtins.derivation`.
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This allows a Nix expression to fall back gracefully on older Nix
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installations that don’t have the desired built-in function.
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- `builtins.compareVersions` s1 s2
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- `builtins.compareVersions` *s1* *s2*
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Compare two strings representing versions and return `-1` if version
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s1 is older than version s2, `0` if they are the same, and `1` if s1
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is newer than s2. The version comparison algorithm is the same as
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the one used by [`nix-env
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*s1* is older than version *s2*, `0` if they are the same, and `1`
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if *s1* is newer than *s2*. The version comparison algorithm is the
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same as the one used by [`nix-env
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-u`](#ssec-version-comparisons).
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- `builtins.concatLists` lists
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- `builtins.concatLists` *lists*
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Concatenate a list of lists into a single list.
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- `builtins.concatStringsSep` separator list
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- `builtins.concatStringsSep` *separator* *list*
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Concatenate a list of strings with a separator between each element,
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e.g. `concatStringsSep "/"
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["usr" "local" "bin"] == "usr/local/bin"`
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@ -76,37 +76,37 @@ For instance, `derivation` is also available as `builtins.derivation`.
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identifier for the Nix installation on which the expression is being
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evaluated, such as `"i686-linux"` or `"x86_64-darwin"`.
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- `builtins.deepSeq` e1 e2
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- `builtins.deepSeq` *e1* *e2*
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This is like `seq
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e1
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e2`, except that e1 is evaluated *deeply*: if it’s a list or set,
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e2`, except that *e1* is evaluated *deeply*: if it’s a list or set,
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its elements or attributes are also evaluated recursively.
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- `derivation` attrs; `builtins.derivation` attrs
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- `derivation` *attrs*; `builtins.derivation` *attrs*
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`derivation` is described in [???](#ssec-derivation).
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- `dirOf` s; `builtins.dirOf` s
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Return the directory part of the string s, that is, everything
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- `dirOf` *s*; `builtins.dirOf` *s*
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Return the directory part of the string *s*, that is, everything
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before the final slash in the string. This is similar to the GNU
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`dirname` command.
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- `builtins.div` e1 e2
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Return the quotient of the numbers e1 and e2.
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- `builtins.div` *e1* *e2*
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Return the quotient of the numbers *e1* and *e2*.
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- `builtins.elem` x xs
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Return `true` if a value equal to x occurs in the list xs, and
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- `builtins.elem` *x* *xs*
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Return `true` if a value equal to *x* occurs in the list *xs*, and
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`false` otherwise.
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- `builtins.elemAt` xs n
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Return element n from the list xs. Elements are counted starting
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- `builtins.elemAt` *xs* *n*
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Return element *n* from the list *xs*. Elements are counted starting
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from 0. A fatal error occurs if the index is out of bounds.
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- `builtins.fetchurl` url
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- `builtins.fetchurl` *url*
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Download the specified URL and return the path of the downloaded
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file. This function is not available if [restricted evaluation
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mode](#conf-restrict-eval) is enabled.
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- `fetchTarball` url; `builtins.fetchTarball` url
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- `fetchTarball` *url*; `builtins.fetchTarball` *url*
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Download the specified URL, unpack it and return the path of the
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unpacked tree. The file must be a tape archive (`.tar`) compressed
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with `gzip`, `bzip2` or `xz`. The top-level path component of the
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@ -142,10 +142,10 @@ For instance, `derivation` is also available as `builtins.derivation`.
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This function is not available if [restricted evaluation
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mode](#conf-restrict-eval) is enabled.
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- `builtins.fetchGit` args
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Fetch a path from git. args can be a URL, in which case the HEAD of
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the repo at that URL is fetched. Otherwise, it can be an attribute
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with the following attributes (all except `url` optional):
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- `builtins.fetchGit` *args*
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Fetch a path from git. *args* can be a URL, in which case the HEAD
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of the repo at that URL is fetched. Otherwise, it can be an
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attribute with the following attributes (all except `url` optional):
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- url
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The URL of the repo.
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@ -240,11 +240,11 @@ For instance, `derivation` is also available as `builtins.derivation`.
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>
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> This behavior is disabled in *Pure evaluation mode*.
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- `builtins.filter` f xs
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Return a list consisting of the elements of xs for which the
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function f returns `true`.
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- `builtins.filter` *f* *xs*
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Return a list consisting of the elements of *xs* for which the
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function *f* returns `true`.
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- `builtins.filterSource` e1 e2
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- `builtins.filterSource` *e1* *e2*
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This function allows you to copy sources into the Nix store while
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filtering certain files. For instance, suppose that you want to use
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the directory `source-dir` as an input to a Nix expression, e.g.
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@ -266,9 +266,9 @@ For instance, `derivation` is also available as `builtins.derivation`.
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./source-dir;
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```
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Thus, the first argument e1 must be a predicate function that is
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Thus, the first argument *e1* must be a predicate function that is
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called for each regular file, directory or symlink in the source
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tree e2. If the function returns `true`, the file is copied to the
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tree *e2*. If the function returns `true`, the file is copied to the
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Nix store, otherwise it is omitted. The function is called with two
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arguments. The first is the full path of the file. The second is a
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string that identifies the type of the file, which is either
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@ -276,19 +276,19 @@ For instance, `derivation` is also available as `builtins.derivation`.
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kinds of files such as device nodes or fifos — but note that those
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cannot be copied to the Nix store, so if the predicate returns
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`true` for them, the copy will fail). If you exclude a directory,
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the entire corresponding subtree of e2 will be excluded.
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the entire corresponding subtree of *e2* will be excluded.
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- `builtins.foldl’` op nul list
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- `builtins.foldl’` *op* *nul* *list*
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Reduce a list by applying a binary operator, from left to right,
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e.g. `foldl’ op nul [x0 x1 x2 ...] = op (op
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(op nul x0) x1) x2) ...`. The operator is applied strictly, i.e.,
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its arguments are evaluated first. For example, `foldl’ (x: y: x +
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y) 0 [1 2 3]` evaluates to 6.
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- `builtins.functionArgs` f
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- `builtins.functionArgs` *f*
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Return a set containing the names of the formal arguments expected
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by the function f. The value of each attribute is a Boolean denoting
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whether the corresponding argument has a default value. For
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by the function *f*. The value of each attribute is a Boolean
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denoting whether the corresponding argument has a default value. For
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instance, `functionArgs ({ x, y ? 123}: ...) = { x = false; y =
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true; }`.
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@ -296,7 +296,7 @@ For instance, `derivation` is also available as `builtins.derivation`.
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the function. Plain lambdas are not included, e.g. `functionArgs (x:
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...) = { }`.
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- `builtins.fromJSON` e
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- `builtins.fromJSON` *e*
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Convert a JSON string to a Nix value. For example,
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builtins.fromJSON ''{"x": [1, 2, 3], "y": null}''
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@ -304,21 +304,22 @@ For instance, `derivation` is also available as `builtins.derivation`.
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returns the value `{ x = [ 1 2 3 ]; y = null;
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}`.
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- `builtins.genList` generator length
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Generate list of size length, with each element i equal to the value
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returned by generator `i`. For example,
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- `builtins.genList` *generator* *length*
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Generate list of size *length*, with each element *i* equal to the
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value returned by *generator* `i`. For example,
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builtins.genList (x: x * x) 5
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returns the list `[ 0 1 4 9 16 ]`.
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- `builtins.getAttr` s set
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`getAttr` returns the attribute named s from set. Evaluation aborts
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if the attribute doesn’t exist. This is a dynamic version of the `.`
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operator, since s is an expression rather than an identifier.
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- `builtins.getAttr` *s* *set*
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`getAttr` returns the attribute named *s* from *set*. Evaluation
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aborts if the attribute doesn’t exist. This is a dynamic version of
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the `.` operator, since *s* is an expression rather than an
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identifier.
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- `builtins.getEnv` s
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`getEnv` returns the value of the environment variable s, or an
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- `builtins.getEnv` *s*
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`getEnv` returns the value of the environment variable *s*, or an
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empty string if the variable doesn’t exist. This function should be
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used with care, as it can introduce all sorts of nasty environment
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dependencies in your Nix expression.
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@ -328,29 +329,29 @@ For instance, `derivation` is also available as `builtins.derivation`.
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Packages. (That is, it does a `getEnv "HOME"` to locate the user’s
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home directory.)
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- `builtins.hasAttr` s set
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`hasAttr` returns `true` if set has an attribute named s, and
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- `builtins.hasAttr` *s* *set*
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`hasAttr` returns `true` if *set* has an attribute named *s*, and
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`false` otherwise. This is a dynamic version of the `?` operator,
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since s is an expression rather than an identifier.
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since *s* is an expression rather than an identifier.
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- `builtins.hashString` type s
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- `builtins.hashString` *type* *s*
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Return a base-16 representation of the cryptographic hash of string
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s. The hash algorithm specified by type must be one of `"md5"`,
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*s*. The hash algorithm specified by *type* must be one of `"md5"`,
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`"sha1"`, `"sha256"` or `"sha512"`.
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- `builtins.hashFile` type p
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- `builtins.hashFile` *type* *p*
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Return a base-16 representation of the cryptographic hash of the
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file at path p. The hash algorithm specified by type must be one of
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`"md5"`, `"sha1"`, `"sha256"` or `"sha512"`.
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file at path *p*. The hash algorithm specified by *type* must be one
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of `"md5"`, `"sha1"`, `"sha256"` or `"sha512"`.
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- `builtins.head` list
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- `builtins.head` *list*
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Return the first element of a list; abort evaluation if the argument
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isn’t a list or is an empty list. You can test whether a list is
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empty by comparing it with `[]`.
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- `import` path; `builtins.import` path
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Load, parse and return the Nix expression in the file path. If path
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is a directory, the file ` default.nix
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- `import` *path*; `builtins.import` *path*
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Load, parse and return the Nix expression in the file *path*. If
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*path* is a directory, the file ` default.nix
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` in that directory is loaded. Evaluation aborts if the file
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doesn’t exist or contains an incorrect Nix expression. `import`
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implements Nix’s module system: you can put any Nix expression (such
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@ -361,7 +362,8 @@ For instance, `derivation` is also available as `builtins.derivation`.
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>
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> Unlike some languages, `import` is a regular function in Nix.
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> Paths using the angle bracket syntax (e.g., `
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> > > > > import` \<foo\>) are normal path values (see [???](#ssec-values)).
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> > > > > import` *\<foo\>*) are normal path values (see
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> [???](#ssec-values)).
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A Nix expression loaded by `import` must not contain any *free
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variables* (identifiers that are not defined in the Nix expression
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@ -393,50 +395,50 @@ For instance, `derivation` is also available as `builtins.derivation`.
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(The function argument doesn’t have to be called `x` in `foo.nix`;
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any name would work.)
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- `builtins.intersectAttrs` e1 e2
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Return a set consisting of the attributes in the set e2 that also
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exist in the set e1.
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- `builtins.intersectAttrs` *e1* *e2*
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Return a set consisting of the attributes in the set *e2* that also
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exist in the set *e1*.
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- `builtins.isAttrs` e
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Return `true` if e evaluates to a set, and `false` otherwise.
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- `builtins.isAttrs` *e*
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Return `true` if *e* evaluates to a set, and `false` otherwise.
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- `builtins.isList` e
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Return `true` if e evaluates to a list, and `false` otherwise.
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- `builtins.isList` *e*
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Return `true` if *e* evaluates to a list, and `false` otherwise.
|
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- `builtins.isFunction` e
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Return `true` if e evaluates to a function, and `false` otherwise.
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- `builtins.isFunction` *e*
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Return `true` if *e* evaluates to a function, and `false` otherwise.
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- `builtins.isString` e
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Return `true` if e evaluates to a string, and `false` otherwise.
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- `builtins.isString` *e*
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Return `true` if *e* evaluates to a string, and `false` otherwise.
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||||
- `builtins.isInt` e
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||||
Return `true` if e evaluates to an int, and `false` otherwise.
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- `builtins.isInt` *e*
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||||
Return `true` if *e* evaluates to an int, and `false` otherwise.
|
||||
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||||
- `builtins.isFloat` e
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||||
Return `true` if e evaluates to a float, and `false` otherwise.
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- `builtins.isFloat` *e*
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||||
Return `true` if *e* evaluates to a float, and `false` otherwise.
|
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- `builtins.isBool` e
|
||||
Return `true` if e evaluates to a bool, and `false` otherwise.
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- `builtins.isBool` *e*
|
||||
Return `true` if *e* evaluates to a bool, and `false` otherwise.
|
||||
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||||
- `builtins.isPath` e
|
||||
Return `true` if e evaluates to a path, and `false` otherwise.
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||||
- `builtins.isPath` *e*
|
||||
Return `true` if *e* evaluates to a path, and `false` otherwise.
|
||||
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||||
- `isNull` e; `builtins.isNull` e
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||||
Return `true` if e evaluates to `null`, and `false` otherwise.
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- `isNull` *e*; `builtins.isNull` *e*
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||||
Return `true` if *e* evaluates to `null`, and `false` otherwise.
|
||||
|
||||
> **Warning**
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||||
>
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||||
> This function is *deprecated*; just write `e == null` instead.
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- `builtins.length` e
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Return the length of the list e.
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||||
- `builtins.length` *e*
|
||||
Return the length of the list *e*.
|
||||
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- `builtins.lessThan` e1 e2
|
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Return `true` if the number e1 is less than the number e2, and
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`false` otherwise. Evaluation aborts if either e1 or e2 does not
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- `builtins.lessThan` *e1* *e2*
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Return `true` if the number *e1* is less than the number *e2*, and
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`false` otherwise. Evaluation aborts if either *e1* or *e2* does not
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||||
evaluate to a number.
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||||
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||||
- `builtins.listToAttrs` e
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||||
- `builtins.listToAttrs` *e*
|
||||
Construct a set from a list specifying the names and values of each
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||||
attribute. Each element of the list should be a set consisting of a
|
||||
string-valued attribute `name` specifying the name of the attribute,
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|
|
@ -451,19 +453,20 @@ For instance, `derivation` is also available as `builtins.derivation`.
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|||
|
||||
{ foo = 123; bar = 456; }
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- `map` f list; `builtins.map` f list
|
||||
Apply the function f to each element in the list list. For example,
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- `map` *f* *list*; `builtins.map` *f* *list*
|
||||
Apply the function *f* to each element in the list *list*. For
|
||||
example,
|
||||
|
||||
map (x: "foo" + x) [ "bar" "bla" "abc" ]
|
||||
|
||||
evaluates to `[ "foobar" "foobla" "fooabc"
|
||||
]`.
|
||||
|
||||
- `builtins.match` regex str
|
||||
- `builtins.match` *regex* *str*
|
||||
Returns a list if the [extended POSIX regular
|
||||
expression](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04)
|
||||
regex matches str precisely, otherwise returns `null`. Each item in
|
||||
the list is a regex group.
|
||||
*regex* matches *str* precisely, otherwise returns `null`. Each item
|
||||
in the list is a regex group.
|
||||
|
||||
builtins.match "ab" "abc"
|
||||
|
||||
|
|
@ -481,21 +484,21 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
|
||||
Evaluates to `[ "foo" ]`.
|
||||
|
||||
- `builtins.mul` e1 e2
|
||||
Return the product of the numbers e1 and e2.
|
||||
- `builtins.mul` *e1* *e2*
|
||||
Return the product of the numbers *e1* and *e2*.
|
||||
|
||||
- `builtins.parseDrvName` s
|
||||
Split the string s into a package name and version. The package name
|
||||
is everything up to but not including the first dash followed by a
|
||||
digit, and the version is everything following that dash. The result
|
||||
is returned in a set `{ name, version }`. Thus,
|
||||
- `builtins.parseDrvName` *s*
|
||||
Split the string *s* into a package name and version. The package
|
||||
name is everything up to but not including the first dash followed
|
||||
by a digit, and the version is everything following that dash. The
|
||||
result is returned in a set `{ name, version }`. Thus,
|
||||
`builtins.parseDrvName "nix-0.12pre12876"` returns `{ name = "nix";
|
||||
version = "0.12pre12876";
|
||||
}`.
|
||||
|
||||
- `builtins.path` args
|
||||
- `builtins.path` *args*
|
||||
An enrichment of the built-in path type, based on the attributes
|
||||
present in args. All are optional except `path`:
|
||||
present in *args*. All are optional except `path`:
|
||||
|
||||
- path
|
||||
The underlying path.
|
||||
|
|
@ -523,20 +526,20 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
providing a hash allows `builtins.path` to be used even when the
|
||||
`pure-eval` nix config option is on.
|
||||
|
||||
- `builtins.pathExists` path
|
||||
Return `true` if the path path exists at evaluation time, and
|
||||
- `builtins.pathExists` *path*
|
||||
Return `true` if the path *path* exists at evaluation time, and
|
||||
`false` otherwise.
|
||||
|
||||
- `builtins.placeholder` output
|
||||
Return a placeholder string for the specified output that will be
|
||||
- `builtins.placeholder` *output*
|
||||
Return a placeholder string for the specified *output* that will be
|
||||
substituted by the corresponding output path at build time. Typical
|
||||
outputs would be `"out"`, `"bin"` or `"dev"`.
|
||||
|
||||
- `builtins.readDir` path
|
||||
Return the contents of the directory path as a set mapping directory
|
||||
entries to the corresponding file type. For instance, if directory
|
||||
`A` contains a regular file `B` and another directory `C`, then
|
||||
`builtins.readDir
|
||||
- `builtins.readDir` *path*
|
||||
Return the contents of the directory *path* as a set mapping
|
||||
directory entries to the corresponding file type. For instance, if
|
||||
directory `A` contains a regular file `B` and another directory `C`,
|
||||
then `builtins.readDir
|
||||
./A` will return the set
|
||||
|
||||
{ B = "regular"; C = "directory"; }
|
||||
|
|
@ -544,33 +547,33 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
The possible values for the file type are `"regular"`,
|
||||
`"directory"`, `"symlink"` and `"unknown"`.
|
||||
|
||||
- `builtins.readFile` path
|
||||
Return the contents of the file path as a string.
|
||||
- `builtins.readFile` *path*
|
||||
Return the contents of the file *path* as a string.
|
||||
|
||||
- `removeAttrs` set list; `builtins.removeAttrs` set list
|
||||
Remove the attributes listed in list from set. The attributes don’t
|
||||
have to exist in set. For instance,
|
||||
- `removeAttrs` *set* *list*; `builtins.removeAttrs` *set* *list*
|
||||
Remove the attributes listed in *list* from *set*. The attributes
|
||||
don’t have to exist in *set*. For instance,
|
||||
|
||||
removeAttrs { x = 1; y = 2; z = 3; } [ "a" "x" "z" ]
|
||||
|
||||
evaluates to `{ y = 2; }`.
|
||||
|
||||
- `builtins.replaceStrings` from to s
|
||||
Given string s, replace every occurrence of the strings in from with
|
||||
the corresponding string in to. For example,
|
||||
- `builtins.replaceStrings` *from* *to* *s*
|
||||
Given string *s*, replace every occurrence of the strings in *from*
|
||||
with the corresponding string in *to*. For example,
|
||||
|
||||
builtins.replaceStrings ["oo" "a"] ["a" "i"] "foobar"
|
||||
|
||||
evaluates to `"fabir"`.
|
||||
|
||||
- `builtins.seq` e1 e2
|
||||
Evaluate e1, then evaluate and return e2. This ensures that a
|
||||
computation is strict in the value of e1.
|
||||
- `builtins.seq` *e1* *e2*
|
||||
Evaluate *e1*, then evaluate and return *e2*. This ensures that a
|
||||
computation is strict in the value of *e1*.
|
||||
|
||||
- `builtins.sort` comparator list
|
||||
Return list in sorted order. It repeatedly calls the function
|
||||
comparator with two elements. The comparator should return `true` if
|
||||
the first element is less than the second, and `false` otherwise.
|
||||
- `builtins.sort` *comparator* *list*
|
||||
Return *list* in sorted order. It repeatedly calls the function
|
||||
*comparator* with two elements. The comparator should return `true`
|
||||
if the first element is less than the second, and `false` otherwise.
|
||||
For example,
|
||||
|
||||
builtins.sort builtins.lessThan [ 483 249 526 147 42 77 ]
|
||||
|
|
@ -581,12 +584,12 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
This is a stable sort: it preserves the relative order of elements
|
||||
deemed equal by the comparator.
|
||||
|
||||
- `builtins.split` regex str
|
||||
- `builtins.split` *regex* *str*
|
||||
Returns a list composed of non matched strings interleaved with the
|
||||
lists of the [extended POSIX regular
|
||||
expression](http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04)
|
||||
regex matches of str. Each item in the lists of matched sequences is
|
||||
a regex group.
|
||||
*regex* matches of *str*. Each item in the lists of matched
|
||||
sequences is a regex group.
|
||||
|
||||
builtins.split "(a)b" "abc"
|
||||
|
||||
|
|
@ -604,44 +607,44 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
|
||||
Evaluates to `[ " " [ "FOO" ] " " ]`.
|
||||
|
||||
- `builtins.splitVersion` s
|
||||
- `builtins.splitVersion` *s*
|
||||
Split a string representing a version into its components, by the
|
||||
same version splitting logic underlying the version comparison in
|
||||
[`nix-env -u`](#ssec-version-comparisons).
|
||||
|
||||
- `builtins.stringLength` e
|
||||
Return the length of the string e. If e is not a string, evaluation
|
||||
is aborted.
|
||||
- `builtins.stringLength` *e*
|
||||
Return the length of the string *e*. If *e* is not a string,
|
||||
evaluation is aborted.
|
||||
|
||||
- `builtins.sub` e1 e2
|
||||
Return the difference between the numbers e1 and e2.
|
||||
- `builtins.sub` *e1* *e2*
|
||||
Return the difference between the numbers *e1* and *e2*.
|
||||
|
||||
- `builtins.substring` start len s
|
||||
Return the substring of s from character position start (zero-based)
|
||||
up to but not including start + len. If start is greater than the
|
||||
length of the string, an empty string is returned, and if start +
|
||||
len lies beyond the end of the string, only the substring up to the
|
||||
end of the string is returned. start must be non-negative. For
|
||||
example,
|
||||
- `builtins.substring` *start* *len* *s*
|
||||
Return the substring of *s* from character position *start*
|
||||
(zero-based) up to but not including *start + len*. If *start* is
|
||||
greater than the length of the string, an empty string is returned,
|
||||
and if *start + len* lies beyond the end of the string, only the
|
||||
substring up to the end of the string is returned. *start* must be
|
||||
non-negative. For example,
|
||||
|
||||
builtins.substring 0 3 "nixos"
|
||||
|
||||
evaluates to `"nix"`.
|
||||
|
||||
- `builtins.tail` list
|
||||
- `builtins.tail` *list*
|
||||
Return the second to last elements of a list; abort evaluation if
|
||||
the argument isn’t a list or is an empty list.
|
||||
|
||||
- `throw` s; `builtins.throw` s
|
||||
Throw an error message s. This usually aborts Nix expression
|
||||
- `throw` *s*; `builtins.throw` *s*
|
||||
Throw an error message *s*. This usually aborts Nix expression
|
||||
evaluation, but in `nix-env -qa` and other commands that try to
|
||||
evaluate a set of derivations to get information about those
|
||||
derivations, a derivation that throws an error is silently skipped
|
||||
(which is not the case for `abort`).
|
||||
|
||||
- `builtins.toFile` name s
|
||||
Store the string s in a file in the Nix store and return its path.
|
||||
The file has suffix name. This file can be used as an input to
|
||||
- `builtins.toFile` *name* *s*
|
||||
Store the string *s* in a file in the Nix store and return its path.
|
||||
The file has suffix *name*. This file can be used as an input to
|
||||
derivations. One application is to write builders “inline”. For
|
||||
instance, the following Nix expression combines [???](#ex-hello-nix)
|
||||
and [???](#ex-hello-builder) into one file:
|
||||
|
|
@ -705,20 +708,20 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
you are using Nixpkgs, the `writeTextFile` function is able to do
|
||||
that.
|
||||
|
||||
- `builtins.toJSON` e
|
||||
Return a string containing a JSON representation of e. Strings,
|
||||
- `builtins.toJSON` *e*
|
||||
Return a string containing a JSON representation of *e*. Strings,
|
||||
integers, floats, booleans, nulls and lists are mapped to their JSON
|
||||
equivalents. Sets (except derivations) are represented as objects.
|
||||
Derivations are translated to a JSON string containing the
|
||||
derivation’s output path. Paths are copied to the store and
|
||||
represented as a JSON string of the resulting store path.
|
||||
|
||||
- `builtins.toPath` s
|
||||
- `builtins.toPath` *s*
|
||||
DEPRECATED. Use `/. + "/path"` to convert a string into an absolute
|
||||
path. For relative paths, use `./. + "/path"`.
|
||||
|
||||
- `toString` e; `builtins.toString` e
|
||||
Convert the expression e to a string. e can be:
|
||||
- `toString` *e*; `builtins.toString` *e*
|
||||
Convert the expression *e* to a string. *e* can be:
|
||||
|
||||
- A string (in which case the string is returned unmodified).
|
||||
|
||||
|
|
@ -735,8 +738,8 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
|
||||
- `null`, which yields the empty string.
|
||||
|
||||
- `builtins.toXML` e
|
||||
Return a string containing an XML representation of e. The main
|
||||
- `builtins.toXML` *e*
|
||||
Return a string containing an XML representation of *e*. The main
|
||||
application for `toXML` is to communicate information with the
|
||||
builder in a more structured format than plain environment
|
||||
variables.
|
||||
|
|
@ -822,22 +825,23 @@ For instance, `derivation` is also available as `builtins.derivation`.
|
|||
of the stylesheet is spliced into the builder using the syntax
|
||||
`xsltproc ${stylesheet}`.
|
||||
|
||||
- `builtins.trace` e1 e2
|
||||
Evaluate e1 and print its abstract syntax representation on standard
|
||||
error. Then return e2. This function is useful for debugging.
|
||||
- `builtins.trace` *e1* *e2*
|
||||
Evaluate *e1* and print its abstract syntax representation on
|
||||
standard error. Then return *e2*. This function is useful for
|
||||
debugging.
|
||||
|
||||
- `builtins.tryEval` e
|
||||
Try to shallowly evaluate e. Return a set containing the attributes
|
||||
`success` (`true` if e evaluated successfully, `false` if an error
|
||||
was thrown) and `value`, equalling e if successful and `false`
|
||||
otherwise. Note that this doesn't evaluate e deeply, so ` let e = {
|
||||
x = throw ""; }; in (builtins.tryEval e).success
|
||||
- `builtins.tryEval` *e*
|
||||
Try to shallowly evaluate *e*. Return a set containing the
|
||||
attributes `success` (`true` if *e* evaluated successfully, `false`
|
||||
if an error was thrown) and `value`, equalling *e* if successful and
|
||||
`false` otherwise. Note that this doesn't evaluate *e* deeply, so
|
||||
` let e = { x = throw ""; }; in (builtins.tryEval e).success
|
||||
` will be `true`. Using ` builtins.deepSeq
|
||||
` one can get the expected result: `let e = { x = throw "";
|
||||
}; in (builtins.tryEval (builtins.deepSeq e e)).success` will be
|
||||
`false`.
|
||||
|
||||
- `builtins.typeOf` e
|
||||
Return a string representing the type of the value e, namely
|
||||
- `builtins.typeOf` *e*
|
||||
Return a string representing the type of the value *e*, namely
|
||||
`"int"`, `"bool"`, `"string"`, `"path"`, `"null"`, `"set"`,
|
||||
`"list"`, `"lambda"` or `"float"`.
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue