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Class: Process::Status

Relationships & Source Files
Inherits: Object
Defined in: process.c,
process.c

Overview

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

Instance Attribute Summary

Instance Method Summary

Instance Attribute Details

#coredump? ⇒ Boolean (readonly)

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

#exited? ⇒ Boolean (readonly)

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

#signaled? ⇒ Boolean (readonly)

Returns true if stat terminated because of an uncaught signal.

#stopped? ⇒ Boolean (readonly)

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

#success? ⇒ Boolean (readonly)

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

Instance Method Details

#&(num) ⇒ Integer

Logical AND of the bits in stat with num.

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

#==(other) ⇒ Boolean

Returns true if the integer value of stat equals other.

#>>(num) ⇒ Integer

Shift the bits in stat right num places.

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

#exitstatus ⇒ Integer?

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

#inspect ⇒ String

Override the inspection method.

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

#pid ⇒ Integer

Returns the process ID that this status object represents.

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

#stopsig ⇒ Integer?

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

#termsig ⇒ Integer?

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

#to_i ⇒ Integer #to_int ⇒ Integer

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

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

#to_s ⇒ String

Show pid and exit status as a string.

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