Platform and Processes

std.platform queries system resources, while std.process handles environment variables and child processes.

System Information

import std.platform;

let host = SystemInfo.hostName();
let os = SystemInfo.os();
let arch = SystemInfo.arch();
let parallelism = CpuInfo.availableParallelism();
let total_memory = MemoryInfo.totalBytes();

SystemInfo.os() and arch() return the underlying system's native lowercase values, such as darwin, linux, arm64, aarch64, or x86_64. These are not the canonical platform names used by Feng build options. Code that checks multiple platforms should account for possible native aliases.

MemoryInfo also provides queries for free, available, and constrained memory, as well as the current process's resident memory.

Environment and Current Process

import std.process;

if Process.hasEnv("HOME") {
  let home = Process.getEnv("HOME");
}

let pid = Process.currentId();
let parent = Process.parentId();

getEnv returns an empty string for a missing environment variable. To distinguish a missing variable from one whose value is empty, call hasEnv first.

Start a Child Process

let child = Process.spawn("printf", "%s", "hello");
let output = child.output();
let code = child.exitCode();

spawn accepts a program path followed by variadic string arguments. The current implementation captures standard output and waits for the process to finish. Use outputBytes() to read raw bytes and isFinished() to confirm that the call has completed.

Do not concatenate untrusted input into a shell command. Pass the program and each argument separately to spawn.