std::env::var_os - Rust
Description: API documentation for the Rust `var_os` fn in crate `std`.
Keywords: rust, rustlang, rust-lang, var_os

# Function std::env::var_os 1.0.0 [−] [src]

    pub fn var_os<K: AsRef<OsStr>>(key: K) -> Option<OsString>

Fetches the environment variable `key` from the current process, returning `None` if the variable isn't set.

# Examples

    use std::env;

    let key = "HOME";
    match env::var_os(key) {
        Some(val) => println!("{}: {:?}", key, val),
        None => println!("{} is not defined in the environment.", key)
    }Run

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand 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`)