Spawn a sub-process from Swift

posix_spawnp.swift

import Glibc

var action = posix_spawn_file_actions_t()
posix_spawn_file_actions_init(&action);
defer { posix_spawn_file_actions_destroy(&action) }
posix_spawn_file_actions_addopen(&action, 1, "/tmp/foo-log", (O_WRONLY | O_CREAT | O_TRUNC), 0644)
posix_spawn_file_actions_adddup2(&action, 1, 2)

let args = [
  "ffmpeg",
  "-version"
]
let argv: [UnsafeMutablePointer<CChar>?] = args.map{ $0.withCString(strdup) }
defer { for case let arg? in argv { free(arg) } }

var pid = pid_t()
let rv = posix_spawnp(&pid, argv[0], &action, nil, argv + [nil], nil)
guard rv == 0 else {
  // Should get errno
  exit(1)
}
print(pid)

var exitCode: Int32 = 0
waitpid(pid, &exitCode, 0)

print("Process exited with code \(exitCode)")