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
               || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_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;         /* NULL-terminated array of pointers
                                          to names of 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; 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

       /etc/group
              local group database file

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────┬───────────────┬─────────────────────────────┐
       │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

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

NOTES

       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

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

COLOPHON

       This  page  is  part  of  release  5.10  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
       https://www.kernel.org/doc/man-pages/.

                                                   2017-09-15                                        GETGRNAM(3)