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.
The Process::UID module contains a collection of module functions which can be used to portably get, set, and switch the current process’s real, effective, and saved user IDs.
The Process::GID module contains a collection of module functions which can be used to portably get, set, and switch the current process’s real, effective, and saved group IDs.