class Process::Status

Process::Status encapsulates the information on the status of a running or terminated system process. The built-in variable $? is either nil or a Process::Status object.

fork { exit 99 }   #=> 26557
Process.wait       #=> 26557
$?.class           #=> Process::Status
$?.to_i            #=> 25344
$? >> 8            #=> 99
$?.stopped?        #=> false
$?.exited?         #=> true
$?.exitstatus      #=> 99

Posix systems record information on processes using a 16-bit integer. The lower bits record the process status (stopped, exited, signaled) and the upper bits possibly contain additional information (for example the program’s return code in the case of exited processes). Pre Ruby 1.8, these bits were exposed directly to the Ruby program. Ruby now encapsulates these in a Process::Status object. To maximize compatibility, however, these objects retain a bit-oriented interface. In the descriptions that follow, when we talk about the integer value of stat, we’re referring to this 16 bit value.

Public Class Methods

Process::Status.wait(pid=-1, flags=0) → Process::Status click to toggle source

Waits for a child process to exit and returns a Process::Status object containing information on that process. Which child it waits on depends on the value of pid:

> 0: Waits for the child whose process ID equals pid.
0: Waits for any child whose process group ID equals that of the calling process.
-1: Waits for any child process (the default if no pid is given).
< -1: Waits for any child whose process group ID equals the absolute value of pid.

The flags argument may be a logical or of the flag values Process::WNOHANG (do not block if no child available) or Process::WUNTRACED (return stopped children that haven’t been reported). Not all flags are available on all platforms, but a flag value of zero will work on all platforms.

Returns nil if there are no child processes. Not available on all platforms.

May invoke the scheduler hook process_wait.

fork { exit 99 }                              #=> 27429
Process::Status.wait                          #=> pid 27429 exit 99
$?                                            #=> nil

pid = fork { sleep 3 }                        #=> 27440
Time.now                                      #=> 2008-03-08 19:56:16 +0900
Process::Status.wait(pid, Process::WNOHANG)   #=> nil
Time.now                                      #=> 2008-03-08 19:56:16 +0900
Process::Status.wait(pid, 0)                  #=> pid 27440 exit 99
Time.now                                      #=> 2008-03-08 19:56:19 +0900

This is an EXPERIMENTAL FEATURE.

VALUE
rb_process_status_waitv(int argc, VALUE *argv, VALUE _)
{
    rb_check_arity(argc, 0, 2);

    rb_pid_t pid = -1;
    int flags = 0;

    if (argc >= 1) {
        pid = NUM2PIDT(argv[0]);
    }

    if (argc >= 2) {
        flags = RB_NUM2INT(argv[1]);
    }

    return rb_process_status_wait(pid, flags);
}

Public Instance Methods

stat & num → integer click to toggle source

Logical AND of the bits in stat with num.

fork { exit 0x37 }
Process.wait
sprintf('%04x', $?.to_i)       #=> "3700"
sprintf('%04x', $? & 0x1e00)   #=> "1600"

static VALUE
pst_bitand(VALUE st1, VALUE st2)
{
    int status = PST2INT(st1) & NUM2INT(st2);

    return INT2NUM(status);
}

stat == other → true or false click to toggle source

Returns true if the integer value of stat equals other.

static VALUE
pst_equal(VALUE st1, VALUE st2)
{
    if (st1 == st2) return Qtrue;
    return rb_equal(pst_to_i(st1), st2);
}

stat >> num → integer click to toggle source

Shift the bits in stat right num places.

fork { exit 99 }   #=> 26563
Process.wait       #=> 26563
$?.to_i            #=> 25344
$? >> 8            #=> 99

static VALUE
pst_rshift(VALUE st1, VALUE st2)
{
    int status = PST2INT(st1) >> NUM2INT(st2);

    return INT2NUM(status);
}

coredump? → true or false click to toggle source

Returns true if stat generated a coredump when it terminated. Not available on all platforms.

static VALUE
pst_wcoredump(VALUE st)
{
#ifdef WCOREDUMP
    int status = PST2INT(st);

    return RBOOL(WCOREDUMP(status));
#else
    return Qfalse;
#endif
}

exited? → true or false click to toggle source

Returns true if stat exited normally (for example using an exit() call or finishing the program).

static VALUE
pst_wifexited(VALUE st)
{
    int status = PST2INT(st);

    return RBOOL(WIFEXITED(status));
}

exitstatus → integer or nil click to toggle source

Returns the least significant eight bits of the return code of stat. Only available if exited? is true.

fork { }           #=> 26572
Process.wait       #=> 26572
$?.exited?         #=> true
$?.exitstatus      #=> 0

fork { exit 99 }   #=> 26573
Process.wait       #=> 26573
$?.exited?         #=> true
$?.exitstatus      #=> 99

static VALUE
pst_wexitstatus(VALUE st)
{
    int status = PST2INT(st);

    if (WIFEXITED(status))
        return INT2NUM(WEXITSTATUS(status));
    return Qnil;
}

inspect → string click to toggle source

Override the inspection method.

system("false")
p $?.inspect #=> "#<Process::Status: pid 12861 exit 1>"

static VALUE
pst_inspect(VALUE st)
{
    rb_pid_t pid;
    int status;
    VALUE str;

    pid = pst_pid(st);
    if (!pid) {
        return rb_sprintf("#<%s: uninitialized>", rb_class2name(CLASS_OF(st)));
    }
    status = PST2INT(st);

    str = rb_sprintf("#<%s: ", rb_class2name(CLASS_OF(st)));
    pst_message(str, pid, status);
    rb_str_cat2(str, ">");
    return str;
}

pid → integer click to toggle source

Returns the process ID that this status object represents.

fork { exit }   #=> 26569
Process.wait    #=> 26569
$?.pid          #=> 26569

static VALUE
pst_pid_m(VALUE self)
{
    rb_pid_t pid = pst_pid(self);
    return PIDT2NUM(pid);
}

signaled? → true or false click to toggle source

Returns true if stat terminated because of an uncaught signal.

static VALUE
pst_wifsignaled(VALUE st)
{
    int status = PST2INT(st);

    return RBOOL(WIFSIGNALED(status));
}

stopped? → true or false click to toggle source

Returns true if this process is stopped. This is only returned if the corresponding wait call had the Process::WUNTRACED flag set.

static VALUE
pst_wifstopped(VALUE st)
{
    int status = PST2INT(st);

    return RBOOL(WIFSTOPPED(status));
}

stopsig → integer or nil click to toggle source

Returns the number of the signal that caused stat to stop (or nil if self is not stopped).

static VALUE
pst_wstopsig(VALUE st)
{
    int status = PST2INT(st);

    if (WIFSTOPPED(status))
        return INT2NUM(WSTOPSIG(status));
    return Qnil;
}

success? → true, false or nil click to toggle source

Returns true if stat is successful, false if not. Returns nil if exited? is not true.

static VALUE
pst_success_p(VALUE st)
{
    int status = PST2INT(st);

    if (!WIFEXITED(status))
        return Qnil;
    return RBOOL(WEXITSTATUS(status) == EXIT_SUCCESS);
}

termsig → integer or nil click to toggle source

Returns the number of the signal that caused stat to terminate (or nil if self was not terminated by an uncaught signal).

static VALUE
pst_wtermsig(VALUE st)
{
    int status = PST2INT(st);

    if (WIFSIGNALED(status))
        return INT2NUM(WTERMSIG(status));
    return Qnil;
}

to_i → integer click to toggle source

Returns the bits in stat as an Integer. Poking around in these bits is platform dependent.

fork { exit 0xab }         #=> 26566
Process.wait               #=> 26566
sprintf('%04x', $?.to_i)   #=> "ab00"

static VALUE
pst_to_i(VALUE self)
{
    int status = pst_status(self);
    return RB_INT2NUM(status);
}

to_s → string click to toggle source

Show pid and exit status as a string.

system("false")
p $?.to_s         #=> "pid 12766 exit 1"

static VALUE
pst_to_s(VALUE st)
{
    rb_pid_t pid;
    int status;
    VALUE str;

    pid = pst_pid(st);
    status = PST2INT(st);

    str = rb_str_buf_new(0);
    pst_message(str, pid, status);
    return str;
}