getgrnam

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 *restrict name, struct group *restrict grp,
                      char *restrict buf, size_t buflen,
                      struct group **restrict result);
       int getgrgid_r(gid_t gid, struct group *restrict grp,
                      char *restrict buf, size_t buflen,
                      struct group **restrict result);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getgrnam_r(), getgrgid_r():
           _POSIX_C_SOURCE
               || /* Glibc <= 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 to indicate the error.  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 5.13 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/.



                                   2021-03-22                        GETGRNAM(3)