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docs: fill out language/types.md#type-path
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@ -190,18 +190,13 @@ This section covers syntax and semantics of the Nix language.
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### Path {#path-literal}
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### Path {#path-literal}
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*Paths* are distinct from strings and can be expressed by path literals such as `./builder.sh`.
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*Paths* can be expressed by path literals such as `./builder.sh`.
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Paths are suitable for referring to local files, and are often preferable over strings.
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- Path values do not contain trailing slashes, `.` and `..`, as they are resolved when evaluating a path literal.
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- Path literals are automatically resolved relative to their [base directory](@docroot@/glossary.md#gloss-base-directory).
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- The files referred to by path values are automatically copied into the Nix store when used in a string interpolation or concatenation.
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- Tooling can recognize path literals and provide additional features, such as autocompletion, refactoring automation and jump-to-file.
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A path literal must contain at least one slash to be recognised as such.
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A path literal must contain at least one slash to be recognised as such.
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For instance, `builder.sh` is not a path:
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For instance, `builder.sh` is not a path:
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it's parsed as an expression that selects the attribute `sh` from the variable `builder`.
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it's parsed as an expression that selects the attribute `sh` from the variable `builder`.
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Path literals are resolved relative to their [base directory](@docroot@/glossary.md#gloss-base-directory).
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Path literals may also refer to absolute paths by starting with a slash.
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Path literals may also refer to absolute paths by starting with a slash.
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> **Note**
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> **Note**
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@ -215,15 +210,6 @@ This section covers syntax and semantics of the Nix language.
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For example, `~/foo` would be equivalent to `/home/edolstra/foo` for a user whose home directory is `/home/edolstra`.
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For example, `~/foo` would be equivalent to `/home/edolstra/foo` for a user whose home directory is `/home/edolstra`.
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Path literals that start with `~` are not allowed in [pure](@docroot@/command-ref/conf-file.md#conf-pure-eval) evaluation.
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Path literals that start with `~` are not allowed in [pure](@docroot@/command-ref/conf-file.md#conf-pure-eval) evaluation.
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Paths can be used in [string interpolation] and string concatenation.
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For instance, evaluating `"${./foo.txt}"` will cause `foo.txt` from the same directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
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Note that the Nix language assumes that all input files will remain _unchanged_ while evaluating a Nix expression.
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For example, assume you used a file path in an interpolated string during a `nix repl` session.
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Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new [store path], since Nix might not re-read the file contents. Use `:r` to reset the repl as needed.
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[store path]: @docroot@/store/store-path.md
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Path literals can also include [string interpolation], besides being [interpolated into other expressions].
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Path literals can also include [string interpolation], besides being [interpolated into other expressions].
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[interpolated into other expressions]: ./string-interpolation.md#interpolated-expressions
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[interpolated into other expressions]: ./string-interpolation.md#interpolated-expressions
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@ -50,8 +50,37 @@ The function [`builtins.isString`](builtins.md#builtins-isString) can be used to
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### Path {#type-path}
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### Path {#type-path}
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<!-- TODO(@rhendric, #10970): Incorporate content from syntax.md#path-literal -->
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A _path_ in the Nix language is an immutable, finite-length sequence of bytes starting with `/`, representing a POSIX-style, canonical file system path.
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Path values are distinct from string values, even if they contain the same sequence of bytes.
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Operations that produce paths will simplify the result as the standard C function [`realpath`] would, except that there is no symbolic link resolution.
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[`realpath`]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/realpath.html
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Paths are suitable for referring to local files, and are often preferable over strings.
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- Path values do not contain trailing or duplicate slashes, `.`, or `..`.
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- Relative path literals are automatically resolved relative to their [base directory].
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- Tooling can recognize path literals and provide additional features, such as autocompletion, refactoring automation and jump-to-file.
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[base directory]: @docroot@/glossary.md#gloss-base-directory
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A file is not required to exist at a given path in order for that path value to be valid, but a path that is converted to a string with [string interpolation] or [string-and-path concatenation] must resolve to a readable file or directory which will be copied into the Nix store.
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For instance, evaluating `"${./foo.txt}"` will cause `foo.txt` from the same directory to be copied into the Nix store and result in the string `"/nix/store/<hash>-foo.txt"`.
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Operations such as [`import`] can also expect a path to resolve to a readable file or directory.
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[string interpolation]: string-interpolation.md#interpolated-expression
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[string-and-path concatenation]: operators.md#string-and-path-concatenation
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[`import`]: builtins.md#builtins-import
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> **Note**
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>
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> The Nix language assumes that all input files will remain _unchanged_ while evaluating a Nix expression.
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> For example, assume you used a file path in an interpolated string during a `nix repl` session.
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> Later in the same session, after having changed the file contents, evaluating the interpolated string with the file path again might not return a new [store path], since Nix might not re-read the file contents.
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> Use `:r` to reset the repl as needed.
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[store path]: @docroot@/store/store-path.md
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Path values can be expressed as [path literals](syntax.md#path-literal).
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The function [`builtins.isPath`](builtins.md#builtins-isPath) can be used to determine if a value is a path.
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The function [`builtins.isPath`](builtins.md#builtins-isPath) can be used to determine if a value is a path.
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### Null {#type-null}
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### Null {#type-null}
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