std::cfg - Rust
Description: API documentation for the Rust `cfg` macro in crate `std`.
Keywords: rust, rustlang, rust-lang, cfg

# 1.0.0[−][src]Macro std::cfg

    macro_rules! cfg {
        ($($cfg:tt)*) => { ... };
    }

Boolean evaluation of configuration flags, at compile-time.

In addition to the `#[cfg]` attribute, this macro is provided to allow boolean expression evaluation of configuration flags. This frequently leads to less duplicated code.

The syntax given to this macro is the same syntax as the `cfg` attribute.

# Examples

    let my_directory = if cfg!(windows) {
        "windows-specific-directory"
    } else {
        "unix-directory"
    };Run

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)