setregid(2)

NAME

     setregid - set real and effective group IDs

SYNOPSIS

     #include <unistd.h>

     int setregid(gid_t rgid, gid_t egid);

DESCRIPTION

     The setregid() function is used to set the real  and  effec-
     tive  group  IDs of the calling process.  If rgid is -1, the
     real group ID is not changed; if egid is -1,  the  effective
     group  ID  is not changed.  The real and effective group IDs
     may be set to different values in the same call.

     If the effective user ID of the calling  process  is  super-
     user,  the  real  group ID and the effective group ID can be
     set to any legal value.

     If the effective user ID  of  the  calling  process  is  not
     super-user, either the real group ID can be set to the saved
     set-group-ID from execve(2), or the effective group  ID  can
     either  be  set  to the saved set-group-ID or the real group
     ID.

     In either case, if the real group ID is being changed  (that
     is,  if  rgid is not -1), or the effective group ID is being
     changed to a value not equal to the real group ID, the saved
     set-group-ID is set equal to the new effective group ID.

RETURN VALUES

     Upon successful completion, 0 is returned. Otherwise, -1  is
     returned, errno is set to indicate the error, and neither of
     the group IDs will be changed.

ERRORS

     The setregid() function will fail if:

     EINVAL
           The value of rgid or egid is less than  0  or  greater
           than UID_MAX (defined in <limits.h>).

     EPERM The calling process's effective UID is not the  super-
           user  and  a change other than changing the real group
           ID to the saved set-group-ID or changing the effective
           group  ID  to the real group ID or the saved group ID,
           was specified.

USAGE

     If a set-group-ID process sets its effective group ID to its
     real  group ID, it can still set its effective group ID back
     to the saved set-group-ID.

SEE ALSO

     execve(2), getgid(2), setreuid(2), setuid(2)