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CentOS 7.0 - man page for getgrnam_r (centos section 3)

GETGRNAM(3)			    Linux Programmer's Manual			      GETGRNAM(3)

       getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry

       #include <sys/types.h>
       #include <grp.h>

       struct group *getgrnam(const char *name);

       struct group *getgrgid(gid_t gid);

       int getgrnam_r(const char *name, struct group *grp,
		 char *buf, size_t buflen, struct group **result);

       int getgrgid_r(gid_t gid, struct group *grp,
		 char *buf, size_t buflen, struct group **result);

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

       getgrnam_r(), getgrgid_r():

       The  getgrnam() function returns a pointer to a structure containing the broken-out fields
       of the record in the group database (e.g., the local group file /etc/group, NIS, and LDAP)
       that matches the group name name.

       The  getgrgid() function returns a pointer to a structure containing the broken-out fields
       of the record in the group database that matches the group ID gid.

       The group structure is defined in <grp.h> as follows:

	   struct group {
	       char   *gr_name;       /* group name */
	       char   *gr_passwd;     /* group password */
	       gid_t   gr_gid;	      /* group ID */
	       char  **gr_mem;	      /* group members */

       For more information about the fields of this structure, see group(5).

       The getgrnam_r() and getgrgid_r() functions obtain the same information as getgrnam()  and
       getgrgid(),  but  store the retrieved group structure in the space pointed to by grp.  The
       string fields pointed to by the members of the group structure are stored  in  the  buffer
       buf  of	size  buflen.	A  pointer to the result (in case of success) or NULL (in case no
       entry was found or an error occurred) is stored in *result.

       The call


       returns either -1, without changing errno, or an initial suggested size for buf.  (If this
       size  is  too small, the call fails with ERANGE, in which case the caller can retry with a
       larger buffer.)

       The getgrnam() and getgrgid() functions return a pointer to a group structure, or NULL  if
       the  matching  entry  is  not  found or an error occurs.  If an error occurs, errno is set
       appropriately.  If one wants to check errno after the call,  it	should	be  set  to  zero
       before the call.

       The return value may point to a static area, and may be overwritten by subsequent calls to
       getgrent(3), getgrgid(), or getgrnam().	(Do not pass the returned pointer to free(3).)

       On success, getgrnam_r() and getgrgid_r() return zero, and set  *result	to  grp.   If  no
       matching  group	record was found, these functions return 0 and store NULL in *result.  In
       case of error, an error number is returned, and NULL is stored in *result.

       0 or ENOENT or ESRCH or EBADF or EPERM or ...
	      The given name or gid was not found.

       EINTR  A signal was caught.

       EIO    I/O error.

       EMFILE The maximum number (OPEN_MAX) of files was open already in the calling process.

       ENFILE The maximum number of files was open already in the system.

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

	      local group database file

   Multithreading (see pthreads(7))
       The getgrnam() and getgrgid() functions are not thread-safe.

       The getgrnam_r() and getgrgid_r() functions are thread-safe.

       SVr4, 4.3BSD, POSIX.1-2001.

       The formulation given above under "RETURN VALUE" is from POSIX.1-2001.  It does	not  call
       "not  found"  an  error, hence does not specify what value errno might have in this situa-
       tion.  But that makes it impossible to recognize errors.  One might argue  that	according
       to  POSIX errno should be left unchanged if an entry is not found.  Experiments on various
       UNIX-like systems shows that lots of different values occur in this situation: 0,  ENOENT,
       EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.

       endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3), group(5)

       This  page  is  part of release 3.53 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

					    2013-07-22				      GETGRNAM(3)

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