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getgroups(2) - getgroups, setgroups, getgroups, setgroups - get/set list of supplementary group IDs - man 2 getgroups

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



NAME
       getgroups, setgroups - get/set(7,n,1 builtins) 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 (of the calling process) are
              returned in(1,8) list.  It is unspecified whether the effective group
              ID  of  the  calling  process  is included in(1,8) 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 modi-
              fied, but the total number of supplementary group  IDs  for  the
              process is returned.

       setgroups
              Sets  the  supplementary group IDs for the process.  Appropriate
              privileges (Linux: the CAP_SETGID capability) are required.

RETURN VALUE
       getgroups
              On success, the number of supplementary group IDs  is  returned.
              On error(8,n), -1 is returned, and errno is set(7,n,1 builtins) appropriately.

       setgroups
              On  success,  zero  is  returned.  On error(8,n), -1 is returned, and
              errno is set(7,n,1 builtins) appropriately.

ERRORS
       EFAULT list has an invalid address.

       EINVAL For setgroups, size  is  greater  than  NGROUPS  (32  for  Linux
              2.0.32).  For getgroups, size is less(1,3) than the number of supple-
              mentary group IDs, but is not zero.

       EPERM  The calling process has  insufficient  privilege  to  call  set-
              groups.

NOTES
       A  process  can have up to at least NGROUPS_MAX supplementary group IDs
       in(1,8) addition to the effective group ID. The set(7,n,1 builtins) 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(3,n) _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(1,8)  SVr3),
       X/OPEN, 4.3BSD.  The getgroups function is in(1,8) POSIX.1.  Since setgroups
       requires privilege, it is not covered by POSIX.1.

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



Linux 2.6.6                       2004-05-27                      GETGROUPS(2)

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