Module env 

Process events, external directories and metadata.

This module contains functions and macros that operate on the executable level, not the app level. Zng apps can have multiple process instances, most common a view-process and app-process pair, plus the crash handler.

The app-process is the normal execution, the other processes use on_process_start! to takeover the process if specific environment variables are set. The process start handlers are called on init!, if a process takeover it exits without returning, so only the normal app-process code executes after init!().

fn main() {
    println!("print in all processes");
    zng::env::init!();
    println!("print only in the app-process");

    // get a path in the app config dir, the config dir is created if needed.
    let my_config = zng::env::config("my-config.txt");

    // read a config file, or create it
    if let Ok(c) = std::fs::read_to_string(&my_config) {
        println!("{c}");
    } else {
        std::fs::write(zng::env::config("my-config.txt"), b"Hello!").unwrap();
    }
}

Note that init must be called in main, it must be called in main to define the lifetime of the processes, this is needed to properly call on_process_exit handlers.

Also see init! docs for details init in "wasm32" and "android" target builds.

Full API

See zng_env for the full API.

Macros

init

Inits process metadata, calls process start handlers and defines the process lifetime in main.

on_process_start

Register a FnOnce(&ProcessStartArgs) closure to be called on init!.

Structs

About

Metadata about the app and main crate.

ProcessExitArgs

Arguments for on_process_exit handlers.

ProcessStartArgs

Arguments for on_process_start handlers.

Functions

about

Gets metadata about the application.

bin

Gets a path relative to the package binaries.

cache

Gets a path relative to the cache directory for the app.

clear_cache

Removes all cache files possible.

config

Gets a path relative to the user config directory for the app.

exit

Terminates the current process with the specified exit code.

init_built_res

Sets a custom path for the “built resources” override checked by res in debug builds.

init_cache

Sets a custom cache path.

init_config

Sets a custom original_config path.

init_res

Sets a custom res path.

migrate_cache

Save new_path as the new cache path and make a best effort to move existing cache files.

migrate_config

Copies all config to new_path and saves it as the config path.

on_process_exit

Register a handler to run once when the current process exits.

process_name

Gets a process runtime name.

res

Gets a path relative to the package resources.