Man Pages

getgroups(2) - phpMan getgroups(2) - phpMan

Command: man perldoc info search(apropos)  


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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       setgroups(): _BSD_SOURCE

DESCRIPTION
       getgroups()  returns  the  supplementary group IDs of the calling process in list.  The argument size should be
       set to the maximum number of items that can be stored in the buffer pointed to by list.  If the calling process
       is  a  member  of  more  than  size supplementary groups, then an error results.  It is unspecified whether the
       effective group ID of the calling process 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.  This allows the caller to determine the size of a dynamically allocated list to be used in a further
       call to getgroups().

       setgroups()  sets  the  supplementary  group  IDs  for the calling process.  Appropriate privileges (Linux: the
       CAP_SETGID capability) are required.  The size argument specifies the number of supplementary group IDs in  the
       buffer pointed to by list.

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

       On success, setgroups() returns 0.  On error, -1 is returned, and errno is set appropriately.

ERRORS
       EFAULT list has an invalid address.

       getgroups() can additionally fail with the following error:

       EINVAL size is less than the number of supplementary group IDs, but is not zero.

       setgroups() can additionally fail with the following errors:

       EINVAL size is greater than NGROUPS_MAX (32 before Linux 2.6.4; 65536 since Linux 2.6.4).

       ENOMEM Out of memory.

       EPERM  The calling process has insufficient privilege.

CONFORMING TO
       SVr4, 4.3BSD.  The getgroups() function is in POSIX.1-2001.  Since setgroups() requires privilege,  it  is  not
       covered by POSIX.1-2001.

NOTES
       A process can have up to 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 preserved across an execve(2).

       The maximum number of supplementary group IDs can be found using sysconf(3):

           long ngroups_max;
           ngroups_max = sysconf(_SC_NGROUPS_MAX);

       The maximum return value of getgroups() cannot be larger than one more than this value.

SEE ALSO
       getgid(2), setgid(2), getgrouplist(3), initgroups(3), capabilities(7), credentials(7)

COLOPHON
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-06-03                      GETGROUPS(2)