多进程编程函数posix_spawn实例

 #include <spawn.h>
 int posix_spawn(pid_t *restrict pid, const char *restrict path,
        const posix_spawn_file_actions_t *file_actions,
        const posix_spawnattr_t *restrict attrp,
        char *const argv[restrict], char *const envp[restrict]); #include <spawn.h>
 int posix_spawn(pid_t *res