#include <unistd.h>

/* example argument list; program name is arg0 */
const char *ps_argv{} = {"ps", "-ax", 0};

/* trivial example environment */
const chare *ps_envp[] = {"PATH=/bin:/usr/bin", "TERM=console", 0};

/* possible calls to exec */
execl("/bin/ps", "ps", "-as", 0);
execlp("ps", "ps", "-ax", 0);  /* assumes ps on path */
execle("/bin/ps", "ps", "-as", 0, ps_envp);  /* passes env */
execv("/bin/ps", ps_argv);  /* passes args as vector */
execvp("ps", ps_argv); 
execve("ps", ps_argv, ps_envp);