getgrgid

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
               || /* 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 bu-
       flen.  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 oc-
       curs.  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 re-
       turned, 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  at-
       tributes(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 sit-
       uation:  0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM, and probably oth-
       ers.

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

COLOPHON
       This  page  is  part of release 5.05 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)