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API Documentation

API Documentation

version 2.110.0

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Function std.process.environment.opBinaryRight

Identify whether a variable is defined in the environment.

bool opBinaryRight(string op : "in")(
  scope const(char)[] name
) @trusted;

Because it doesn't return the value, this function is cheaper than get. However, if you do need the value as well, you should just check the return of get for null instead of using this function first.

Example

// good usage
if ("MY_ENV_FLAG" in environment)
    doSomething();

// bad usage
if ("MY_ENV_VAR" in environment)
    doSomething(environment["MY_ENV_VAR"]);

// do this instead
if (auto var = environment.get("MY_ENV_VAR"))
    doSomething(var);

Authors

Lars Tandle Kyllingstad, Steven Schveighoffer, Vladimir Panteleev

License

Boost License 1.0.