setgroups

GETGROUPS(2)		  Linux Programmer’s Manual		 GETGROUPS(2)



NAME
       getgroups, setgroups - get/set list of supplementary group IDs

SYNOPSIS
       #include <sys/types.h>
       #include <unistd.h>

       int getgroups(int size, gid_t list[]);

       #include <grp.h>

       int setgroups(size_t size, const gid_t *list);

DESCRIPTION
       getgroups
	      Up to size supplementary group IDs are returned in list.	It is
	      unspecified whether the effective group ID of the calling	 pro-
	      cess  is	included  in the returned list. (Thus, an application
	      should also call getegid(2) and add  or  remove  the  resulting
	      value.)	If  size is zero, list is not modified, but the total
	      number of supplementary group IDs for the process is  returned.

       setgroups
	      Sets  the	 supplementary	group  IDs for the process.  Only the
	      super-user may use this function.

RETURN VALUE
       getgroups
	      On success, the number of supplementary group IDs is  returned.
	      On error, -1 is returned, and errno is set appropriately.

       setgroups
	      On  success,  zero  is returned.	On error, -1 is returned, and
	      errno is set appropriately.

ERRORS
       EFAULT list has an invalid address.

       EPERM  For setgroups, the user is not the super-user.

       EINVAL For setgroups, size is  greater  than  NGROUPS  (32  for	Linux
	      2.0.32).	 For  getgroups, size is less than the number of sup-
	      plementary group IDs, but is not zero.

NOTES
       A process can have up to at least NGROUPS_MAX supplementary group  IDs
       in  addition to the effective group ID. The set of supplementary group
       IDs is inherited from the parent process and may be changed using set-
       groups.	 The  maximum  number of supplementary group IDs can be found
       using sysconf(3):
	   long ngroups_max;
	   ngroups_max = sysconf(_SC_NGROUPS_MAX);
       The maximal return value of getgroups cannot be larger than  one	 more
       than the value obtained this way.

       The  prototype  for  setgroups  is  only	 available  if _BSD_SOURCE is
       defined	(either	 explicitly,   or   implicitly,	  by   not   defining
       _POSIX_SOURCE or compiling with the -ansi flag).

CONFORMING TO
       SVr4,  SVID  (issue  4  only;  these  calls were not present in SVr3),
       X/OPEN,	4.3BSD.	  The  getgroups  function  is	in  POSIX.1.	Since
       setgroups requires privilege, it is not covered by POSIX.1.

SEE ALSO
       initgroups(3), getgid(2), setgid(2)



Linux 2.0.32			  1997-12-10			 GETGROUPS(2)