mirror of
https://github.com/privatevoid-net/nix-super.git
synced 2024-11-28 16:46:16 +02:00
31313d1401
They are equivalent according to <https://spec.commonmark.org/0.29/#hard-line-breaks>, and the trailing spaces tend to be a pain (because the make git complain, editors tend to want to remove them − the `.editorconfig` actually specifies that − etc..).
158 lines
4.2 KiB
Markdown
158 lines
4.2 KiB
Markdown
# Name
|
||
|
||
`nix-instantiate` - instantiate store derivations from Nix expressions
|
||
|
||
# Synopsis
|
||
|
||
`nix-instantiate`
|
||
[`--parse` | `--eval` [`--strict`] [`--json`] [`--xml`] ]
|
||
[`--read-write-mode`]
|
||
[`--arg` *name* *value*]
|
||
[{`--attr`| `-A`} *attrPath*]
|
||
[`--add-root` *path*]
|
||
[`--expr` | `-E`]
|
||
*files…*
|
||
|
||
`nix-instantiate` `--find-file` *files…*
|
||
|
||
# Description
|
||
|
||
The command `nix-instantiate` generates [store
|
||
derivations](../glossary.md) from (high-level) Nix expressions. It
|
||
evaluates the Nix expressions in each of *files* (which defaults to
|
||
*./default.nix*). Each top-level expression should evaluate to a
|
||
derivation, a list of derivations, or a set of derivations. The paths
|
||
of the resulting store derivations are printed on standard output.
|
||
|
||
If *files* is the character `-`, then a Nix expression will be read from
|
||
standard input.
|
||
|
||
# Options
|
||
|
||
- `--add-root` *path*\
|
||
See the [corresponding option](nix-store.md) in `nix-store`.
|
||
|
||
- `--parse`\
|
||
Just parse the input files, and print their abstract syntax trees on
|
||
standard output in ATerm format.
|
||
|
||
- `--eval`\
|
||
Just parse and evaluate the input files, and print the resulting
|
||
values on standard output. No instantiation of store derivations
|
||
takes place.
|
||
|
||
- `--find-file`\
|
||
Look up the given files in Nix’s search path (as specified by the
|
||
`NIX_PATH` environment variable). If found, print the corresponding
|
||
absolute paths on standard output. For instance, if `NIX_PATH` is
|
||
`nixpkgs=/home/alice/nixpkgs`, then `nix-instantiate --find-file
|
||
nixpkgs/default.nix` will print `/home/alice/nixpkgs/default.nix`.
|
||
|
||
- `--strict`\
|
||
When used with `--eval`, recursively evaluate list elements and
|
||
attributes. Normally, such sub-expressions are left unevaluated
|
||
(since the Nix expression language is lazy).
|
||
|
||
> **Warning**
|
||
>
|
||
> This option can cause non-termination, because lazy data
|
||
> structures can be infinitely large.
|
||
|
||
- `--json`\
|
||
When used with `--eval`, print the resulting value as an JSON
|
||
representation of the abstract syntax tree rather than as an ATerm.
|
||
|
||
- `--xml`\
|
||
When used with `--eval`, print the resulting value as an XML
|
||
representation of the abstract syntax tree rather than as an ATerm.
|
||
The schema is the same as that used by the [`toXML`
|
||
built-in](../expressions/builtins.md).
|
||
|
||
- `--read-write-mode`\
|
||
When used with `--eval`, perform evaluation in read/write mode so
|
||
nix language features that require it will still work (at the cost
|
||
of needing to do instantiation of every evaluated derivation). If
|
||
this option is not enabled, there may be uninstantiated store paths
|
||
in the final output.
|
||
|
||
<!-- end list -->
|
||
|
||
# Examples
|
||
|
||
Instantiating store derivations from a Nix expression, and building them
|
||
using `nix-store`:
|
||
|
||
```console
|
||
$ nix-instantiate test.nix (instantiate)
|
||
/nix/store/cigxbmvy6dzix98dxxh9b6shg7ar5bvs-perl-BerkeleyDB-0.26.drv
|
||
|
||
$ nix-store -r $(nix-instantiate test.nix) (build)
|
||
...
|
||
/nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26 (output path)
|
||
|
||
$ ls -l /nix/store/qhqk4n8ci095g3sdp93x7rgwyh9rdvgk-perl-BerkeleyDB-0.26
|
||
dr-xr-xr-x 2 eelco users 4096 1970-01-01 01:00 lib
|
||
...
|
||
```
|
||
|
||
You can also give a Nix expression on the command line:
|
||
|
||
```console
|
||
$ nix-instantiate -E 'with import <nixpkgs> { }; hello'
|
||
/nix/store/j8s4zyv75a724q38cb0r87rlczaiag4y-hello-2.8.drv
|
||
```
|
||
|
||
This is equivalent to:
|
||
|
||
```console
|
||
$ nix-instantiate '<nixpkgs>' -A hello
|
||
```
|
||
|
||
Parsing and evaluating Nix expressions:
|
||
|
||
```console
|
||
$ nix-instantiate --parse -E '1 + 2'
|
||
1 + 2
|
||
```
|
||
|
||
```console
|
||
$ nix-instantiate --eval -E '1 + 2'
|
||
3
|
||
```
|
||
|
||
```console
|
||
$ nix-instantiate --eval --xml -E '1 + 2'
|
||
<?xml version='1.0' encoding='utf-8'?>
|
||
<expr>
|
||
<int value="3" />
|
||
</expr>
|
||
```
|
||
|
||
The difference between non-strict and strict evaluation:
|
||
|
||
```console
|
||
$ nix-instantiate --eval --xml -E 'rec { x = "foo"; y = x; }'
|
||
...
|
||
<attr name="x">
|
||
<string value="foo" />
|
||
</attr>
|
||
<attr name="y">
|
||
<unevaluated />
|
||
</attr>
|
||
...
|
||
```
|
||
|
||
Note that `y` is left unevaluated (the XML representation doesn’t
|
||
attempt to show non-normal forms).
|
||
|
||
```console
|
||
$ nix-instantiate --eval --xml --strict -E 'rec { x = "foo"; y = x; }'
|
||
...
|
||
<attr name="x">
|
||
<string value="foo" />
|
||
</attr>
|
||
<attr name="y">
|
||
<string value="foo" />
|
||
</attr>
|
||
...
|
||
```
|