os

Environment

env(name) is the variable’s value, or nil if unset; setEnv(name, v) and unsetEnv(name) change it, and environ() is all of it as an object. platform is "darwin", "linux", "windows", …

let port = int(os.env("PORT") ?? "8080");
print(port);                    // 8080

os.setEnv("APP_MODE", "test");
print(os.env("APP_MODE"));      // test
os.unsetEnv("APP_MODE");
print(os.env("APP_MODE"));      // nil

print(os.environ().has("PATH")); // true
let shell = os.platform == "windows" ? "cmd" : "sh";
print(shell);                   // sh

exec

exec(cmd[, args[, opts]]) runs cmd with the array of string args and waits; it returns ExecResult { code, stdout, stderr }. A non-zero exit is not an error; a command not found is an IOError with code notFound.

opts is an ExecOptions { input, dir, env }, or an object converted to one: input is stdin, dir the working directory, env an object added to the current environment; all are optional.

let r = os.exec("echo", ["hello", "world"]);
print(r);   // ExecResult {code: 0, stdout: "hello world\n", stderr: ""}

let up = os.exec("tr", ["a-z", "A-Z"], { input: "shout\n" });
print(up.stdout.trim());   // SHOUT

let greet = os.exec("sh", ["-c", "echo $GREETING"], { env: { GREETING: "hi" } });
print(greet.stdout.trim()); // hi

let ls = os.exec("ls", ["/no/such/dir"]);
print(ls.code);             // 1

try {
    os.exec("no-such-command");
} catch e is IOError {
    print(e.code);          // notFound
}

exit

exit([code]) exits with code, 0 to 255, default 0, at once; try does not catch it. To exit from the end of the program, return the code from main.

// status.rn
let r = os.exec("git", ["status", "--short"]);
if r.code != 0 {
    io.eprint(r.stderr.trim());
    os.exit(r.code);
}
io.write(r.stdout);

$ rune run status.rn; echo "exit $?"    # outside a git repository
fatal: not a git repository (or any of the parent directories): .git
exit 128