huschi.net

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

NAME
       getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry
SYNOPSIS
       #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():
           _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
           _SVID_SOURCE || _POSIX_SOURCE
DESCRIPTION
       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
           sysconf(_SC_GETGR_R_SIZE_MAX)
       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.)
RETURN VALUE
       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.
ERRORS
       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.
FILES
       /etc/group
              local group database file
ATTRIBUTES
   Multithreading (see pthreads(7))
       The getgrnam() and getgrgid() functions are not thread-safe.
       The getgrnam_r() and getgrgid_r() functions are thread-safe.
CONFORMING TO
       SVr4, 4.3BSD, POSIX.1-2001.
NOTES
       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 situation.  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 var-
       ious UNIX-like systems shows that lots of  different  values  occur  in
       this  situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and proba-
       bly others.
SEE ALSO
       endgrent(3),  fgetgrent(3),  getgrent(3),   getpwnam(3),   setgrent(3),
       group(5)
COLOPHON
       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 http://www.kernel.org/doc/man-pages/.

                                  2013-07-22                       GETGRNAM(3)