fork

Library for creating a new process detached from the controlling terminal (daemon).

Why?

• Minimal library to daemonize, fork, double-fork a process.
• daemon(3) has been deprecated in MacOSX 10.5, by using fork and setsid syscalls, new methods can be created to achieve the same goal.

Example:

Create a new test project:

$ cargo new --bin fork

To install cargo use: curl https://sh.rustup.rs -sSf | sh

Edit fork/Cargo.toml and add to [dependencies]:

fork = "0.1"

Add the following code to fork/main.rs

use fork::{daemon, Fork};
use std::process::Command;

fn main() {
    if let Ok(Fork::Child) = daemon(false, false) {
        Command::new("sleep")
            .arg("300")
            .output()
            .expect("failed to execute process");
    }
}

If using daemon(false, false),it will chdir to / and close the standard input, standard output, and standard error file descriptors.

Test running:

$ cargo run

Use ps to check the process, for example:

$ ps -axo ppid,pid,pgid,sess,tty,tpgid,stat,uid,%mem,%cpu,command, | egrep "fork|sleep|PID"

egrep is used to show the ps headers

Output should be something like:

 PPID   PID  PGID   SESS TTY      TPGID STAT   UID       %MEM  %CPU COMMAND
    1 48738 48737      0 ??           0 S      501        0.0   0.0 target/debug/fork
48738 48753 48737      0 ??           0 S      501        0.0   0.0 sleep 300

• PPID == 1 that's the parent process

• TTY = ?? no controlling terminal

• new PGID = 48737

  1 - root (init/launchd)
   \-- 48738 fork         PGID - 48737
    \--- 48753 sleep      PGID - 48737