method

system

v2_6_3 - Show latest stable - Class: Kernel

system(*args)

public

Executes command… in a subshell. command… is one of following forms.

commandline                 : command line string which is passed to the standard shell
cmdname, arg1, ...          : command name and one or more arguments (no shell)
[cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)

system returns true if the command gives zero exit status, false for non zero exit status. Returns nil if command execution fails. An error status is available in $?. The arguments are processed in the same way as for Kernel.spawn.

The hash arguments, env and options, are same as exec and spawn. See Kernel.spawn for details.

system("echo *")
system("echo", "*")

produces:

config.h main.rb
*

See Kernel.exec for the standard shell.

static VALUE
rb_f_system(int argc, VALUE *argv)
{
    /*
     * n.b. using alloca for now to simplify future Thread::Light code
     * when we need to use malloc for non-native Fiber
     */
    struct waitpid_state *w = alloca(sizeof(struct waitpid_state));
    rb_pid_t pid; /* may be different from waitpid_state.pid on exec failure */
    VALUE execarg_obj;
    struct rb_execarg *eargp;
    int exec_errnum;

    execarg_obj = rb_execarg_new(argc, argv, TRUE, TRUE);
    eargp = rb_execarg_get(execarg_obj);
    w->ec = GET_EC();
    waitpid_state_init(w, 0, 0);
    eargp->waitpid_state = w;
    pid = rb_execarg_spawn(execarg_obj, 0, 0);
    exec_errnum = pid < 0 ? errno : 0;

#if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
    if (w->pid > 0) {
        /* `pid' (not w->pid) may be < 0 here if execve failed in child */
        if (WAITPID_USE_SIGCHLD) {
            rb_ensure(waitpid_sleep, (VALUE)w, waitpid_cleanup, (VALUE)w);
        }
        else {
            waitpid_no_SIGCHLD(w);
        }
        rb_last_status_set(w->status, w->ret);
    }
#endif
    if (w->pid < 0 /* fork failure */ || pid < 0 /* exec failure */) {
        if (eargp->exception) {
            int err = exec_errnum ? exec_errnum : w->errnum;
            VALUE command = eargp->invoke.sh.shell_script;
            RB_GC_GUARD(execarg_obj);
            rb_syserr_fail_str(err, command);
        }
        else {
            return Qnil;
        }
    }
    if (w->status == EXIT_SUCCESS) return Qtrue;
    if (eargp->exception) {
        VALUE command = eargp->invoke.sh.shell_script;
        VALUE str = rb_str_new_cstr("Command failed with");
        rb_str_cat_cstr(pst_message_status(str, w->status), ": ");
        rb_str_append(str, command);
        RB_GC_GUARD(execarg_obj);
        rb_exc_raise(rb_exc_new_str(rb_eRuntimeError, str));
    }
    else {
        return Qfalse;
    }
}

system

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