id options
              This  command  provides a means of getting, setting
              and converting user, group and process ids.  The id
              command has the following options:

            id user ?name?

            id userid ?uid?
                   Set  the real and effective user ID to name or
                   uid, if the name (or uid) is valid and permis-
                   sions  allow  it.  If the name (or uid) is not
                   specified,  the  current  name  (or  uid)   is
                   returned.

            id convert userid uid

            id convert user name
                   Convert  a  user  ID number to a user name, or
                   vice versa.

            id group ?name?

            id groupid ?gid?
                   Set the real and effective group ID to name or
                   gid, if the name (or gid) is valid and permis-
                   sions allow it.  If the group name (or gid) is
                   not specified, the current group name (or gid)
                   is returned.

            id convert groupid gid

            id convert group name
                   Convert a group ID number to a group name,  or
                   vice versa.

            id effective user

            id effective userid
                   Return  the  effective user name, or effective
                   user ID number, respectively.

            id effective group

            id effective groupid
                   Return the effective group name, or  effective
                   group ID number, respectively.

            id process
                   Return  the process ID of the current process.

            id process parent
                   Return the process ID of  the  parent  of  the
                   current process.
            id process group
                   Return  the  process  group  ID of the current
                   process.

            id process group set
                   Set the process group ID of the  current  pro-
                   cess to its process ID.

       This command is provided by Extended Tcl.