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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).

       ┌──────────────┬───────────────┬─────────────────────────────┐
       │InterfaceAttributeValue                       │
       ├──────────────┼───────────────┼─────────────────────────────┤
       │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 5.01 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)