getgrnam_r(3) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       #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():
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION         top

       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;         /* NULL-terminated array of pointers
                                          to names of group members */

       For more information about the fields of this structure, see

       The getgrnam_r() and getgrgid_r() functions obtain the same informa‐
       tion 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 *re‐

       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.)

RETURN VALUE         top

       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         top

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

       EINTR  A signal was caught; see signal(7).

       EIO    I/O error.

       EMFILE The per-process limit on the number of open file descriptors
              has been reached.

       ENFILE The system-wide limit on the total number of open files has
              been reached.

       ENOMEM Insufficient memory to allocate group structure.

       ERANGE Insufficient buffer space supplied.

FILES         top

              local group database file

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface     Attribute     Value                       │
       │getgrnam()    │ Thread safety │ MT-Unsafe race:grnam locale │
       │getgrgid()    │ Thread safety │ MT-Unsafe race:grgid locale │
       │getgrnam_r(), │ Thread safety │ MT-Safe locale              │
       │getgrgid_r()  │               │                             │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.

NOTES         top

       The formulation given above under "RETURN VALUE" is from POSIX.1.  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
       various UNIX-like systems show that lots of different values occur in
       this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and
       probably others.

SEE ALSO         top

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

COLOPHON         top

       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2017-09-15                      GETGRNAM(3)