Crate subst

source ·
Expand description

Shell-like variable substitution for strings and byte strings.

Features

  • Perform substitution in &str or in &[u8].
  • Provide a custom map of variables or use environment variables.
  • Short format: "Hello $name!"
  • Long format: "Hello ${name}!"
  • Default values: "Hello ${name:person}!"
  • Recursive substitution in default values: "${XDG_CONFIG_HOME:$HOME/.config}/my-app/config.toml"
  • Perform substitution on all string values in YAML data (optional, requires the yaml feature).

Variable names can consist of alphanumeric characters and underscores. They are allowed to start with numbers.

Examples

The substitute() function can be used to perform substitution on a &str. The variables can either be a HashMap or a BTreeMap.

let mut variables = HashMap::new();
variables.insert("name", "world");
assert_eq!(subst::substitute("Hello $name!", &variables)?, "Hello world!");

The variables can also be taken directly from the environment with the Env map.

assert_eq!(
  subst::substitute("$XDG_CONFIG_HOME/my-app/config.toml", &subst::Env)?,
  "/home/user/.config/my-app/config.toml",
);

Substitution can also be done on byte strings using the substitute_bytes() function.

let mut variables = HashMap::new();
variables.insert("name", b"world");
assert_eq!(subst::substitute_bytes(b"Hello $name!", &variables)?, b"Hello world!");

Re-exports

Modules

  • error
    Module containing error details.
  • yaml
    Support for variable substitution in YAML data.

Structs

  • Env
    A map that gives strings from the environment.
  • EnvBytes
    A map that gives byte strings from the environment.
  • NoSubstitution
    A “map” that never returns any values.

Enums

Traits

  • VariableMap
    Trait for types that can be used as a variable map.

Functions