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 *gbuf,
                 char *buf, size_t buflen, struct group **gbufp);

       int getgrgid_r(gid_t gid, struct group *gbuf,
                 char *buf, size_t buflen, struct group **gbufp);

DESCRIPTION
       The  getgrnam() function returns a pointer to a structure containing the group information
       from /etc/group for the entry that matches the group name name.

       The getgrgid() function returns a pointer to a structure containing the group  information
       from /etc/group for the entry that matches the group gid gid.

       The  getgrnam_r()  and  getgrgid_r()  functions  find  the same information, but store the
       retrieved group structure in the space pointed to by gbuf.  This group structure  contains
       pointers  to  strings,  and  these strings 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 *gbufp.

       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;      /* group members */
              };

       The   maximum   needed   size   for   buf   can   be   found  using  sysconf(3)  with  the
       _SC_GETGR_R_SIZE_MAX parameter. A call to sysconf( _SC_GETGR_R_SIZE_MAX )  returns  either
       -1 without changing errno or an initial value suggested for the size of this buffer.

RETURN VALUE
       The  getgrnam()  and getgrgid() functions return a pointer to the group information struc-
       ture, 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 static area, and may be overwritten by subsequent  calls  to
       getgrent(), getgrgid(), or getgrnam().

       The   getgrnam_r() and getgrgid_r() functions return zero on success. In case of error, an
       error value is returned.

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

       ENOMEM Insufficient memory.

       EIO    I/O error.

       EINTR  A signal was caught.

       EMFILE The maximum number (OPEN_MAX) of files was open already in the calling process.

       ENFILE The maximum number of files was open already in the system.

       ERANGE Insufficient buffer space supplied.

FILES
       /etc/group
              group database file

CONFORMING TO
       SVID 3, BSD 4.3, POSIX 1003.1-2003

NOTES
       The formulation given above under "RETURN VALUE" is from POSIX 1003.1-2001.  It  does  not
       call "not found" an error, hence does not specify what value errno might have in this sit-
       uation. 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 shows that lots of different values occur in this situation: 0,  ENOENT,
       EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.

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



                                            2003-11-15                                GETGRNAM(3)