operating system services getgid(returns the real group id of the process (unixgetgroups(returns list of integer group ids to which the process owner belongs (unixgetlogin(returns the user name associated with the effective user id (unixgetpgid(pidreturns the process group id of the process with process id pid if pid is the process group of the calling process is returned (unixgetpgrp(returns the id of the current process group process groups are typically used in conjunction with job control the process group is not necessarily the same as the group id of the process (unixgetpid(returns the real process id of the current process (unix and windowsgetppid(returns the process id of the parent process (unixgetsid(pidreturns the process session identifier of process pid if pid is the identifier of the current process is returned (unixgetuid(returns the real user id of the current process (unixputenv(varnamevaluesets environment variable varname to value changes affect subprocesses started with os system()popen()fork()and execv(assignments to items in os environ automatically call putenv(howevercalls to putenv(don' update os environ (unix and windowssetegid(egidsets the effective group id (unixseteuid(euidsets the effective user id (unixsetgid(gidsets the group id of the current process (unixsetgroups(groupssets the group access list of the current process groups is sequence of integers specifying group identifiers can only be called by root (unixf lib fl ff