In order:
pid: The is the process ID (PID) of the process you call theProcess.pidmethod in.ppid: The PID of the parent process (the process that spawned the current one). For example, if you runruby test.rbin a bash shell, PPID in that process would be the PID of Bash.uid: The UNIX ID of the user the process is running under.euid: The effective user ID that the process is running under. The EUID determines what a program is allowed to do, based on what the user with this UID is allowed to do. Typically the same asuid, but can be different with commands likesudo.gid: The UNIX group ID the program is running under.egid: Likeeuid, but for groups.