Crate realia

Realia provides attribute macros for conditional compilation, analogous to #[cfg(...)] and #[cfg_attr(...)].

Attribute Macros

all	Checks if multiple conditions are met.
any	Checks if at least one of multiple conditions is met.
attr	Applies an attribute when the condition is met. You can also specify const this way.
cmd	Checks whether an executable exists on the PATH.
dep	Checks whether a crate has a certain dependency and optionally if that dependency is a certain version.
dep_before	Checks whether a crate has a certain dependency below a certain version.
dep_from_registry	Checks whether a crate has a certain dependency installed from the registry (as opposed to being a Git dependency or a path dependency). This is useful if you have non-registry dependencies with a registry fallback for publishing.
dep_since	Checks whether a crate has a certain dependency at or above a certain version.
env	Checks whether an environment variable is defined and optionally what value it has.
not	Inverts another condition.