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 supple-
              mentary 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.

SEE ALSO

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

Linux 2.0.32                      1997-12-10                      getgroups(2)