getgrent_r(3) - NetBSD Manual Pages

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GETGRENT(3)             NetBSD Library Functions Manual            GETGRENT(3)


NAME

     getgrent, getgrent_r, getgrgid, getgrgid_r, getgrnam, getgrnam_r,
     setgroupent, setgrent, endgrent -- group database operations


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <grp.h>

     struct group *
     getgrent(void);

     int
     getgrent_r(struct group *grp, char *buffer, size_t buflen,
         struct group **result);

     struct group *
     getgrgid(gid_t gid);

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

     struct group *
     getgrnam(const char *name);

     int
     getgrnam_r(const char *name, struct group *grp, char *buffer,
         size_t buflen, struct group **result);

     int
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);


DESCRIPTION

     These functions operate on the group database which is described in
     group(5).  Each line of the database is defined by the structure group
     found in the include file <grp.h>:

           struct group {
                   char    *gr_name;       /* group name */
                   char    *gr_passwd;     /* group password */
                   gid_t   gr_gid;         /* group id */
                   char    **gr_mem;       /* group members */
           };

     The functions getgrnam() and getgrgid() search the group database for the
     given group name pointed to by name or the group id pointed to by gid,
     respectively, returning the first one encountered.  Identical group names
     or group ids may result in undefined behavior.

     The getgrent() function sequentially reads the group database and is
     intended for programs that wish to step through the complete list of
     groups.

     All three functions will open the group file for reading, if necessary.

     The functions getgrnam_r(), getgrgid_r(), and getgrent_r() act like their
     non re-entrant counterparts respectively, updating the contents of grp
     and storing a pointer to that in result, and returning 0.  Storage used
     by grp is allocated from buffer, which is buflen bytes in size.  If the
     requested entry cannot be found, result will point to NULL and 0 will be
     returned.  If an error occurs, a non-zero error number will be returned
     and result will point to NULL.  Calling getgrent_r() from multiple
     threads will result in each thread reading a disjoint portion of the
     group database.

     The setgroupent() function opens the file, or rewinds it if it is already
     open.  If stayopen is non-zero, file descriptors are left open, signifi-
     cantly speeding functions subsequent calls.  This functionality is unnec-
     essary for getgrent() as it doesn't close its file descriptors by
     default.  It should also be noted that it is dangerous for long-running
     programs to use this functionality as the group file may be updated.

     The setgrent() function is equivalent to setgroupent() with an argument
     of zero.

     The endgrent() function closes any open files.


RETURN VALUES

     The functions getgrgid(), getgrnam(), and getgrent() return a valid
     pointer to a group structure on success and a NULL pointer if the entry
     was not found or an error occurred.  If an error occurred, the global
     variable errno is set to indicate the nature of the failure.

     The functions getgrgid_r(), getgrnam_r(), and getgrent_r() return 0 on
     success or entry not found, and non-zero on failure, setting the global
     variable errno to indicate the nature of the failure.

     The setgroupent() function returns the value 1 if successful, otherwise
     the value 0 is returned, setting the global variable errno to indicate
     the nature of the failure.

     The endgrent() and setgrent() functions have no return value.


FILES

     /etc/group  group database file


COMPATIBILITY

     The historic function setgrfile(), which allowed the specification of
     alternative group databases, has been deprecated and is no longer avail-
     able.


ERRORS

     The following error codes may be set in errno for getgrent, getgrent_r,
     getgrnam, getgrnam_r, getgrgid, getgrgid_r, and setgroupent:

     [EINTR]            A signal was caught during the database search.

     [EIO]              An I/O error has occurred.

     [EMFILE]           The limit on open files for this process has been
                        reached.

     [ENFILE]           The system limit on open files has been reached.

     The following error code may be set in errno for getgrent_r, getgrnam_r,
     and getgrgid_r:

     [ERANGE]           The resulting struct group does not fit in the space
                        defined by buffer and buflen

     Other errno values may be set depending on the specific database back-
     ends.


SEE ALSO

     getpwent(3), group(5), nsswitch.conf(5)


STANDARDS

     The getgrgid() and getgrnam() functions conform to ISO/IEC 9945-1:1990
     (``POSIX.1'').  The getgrgid_r() and getgrnam_r() functions conform to
     IEEE Std 1003.1c-1995 (``POSIX.1'').  The endgrent(), getgrent(), and
     setgrent() functions conform to X/Open Portability Guide Issue 4,
     Version 2 (``XPG4.2'') and IEEE Std 1003.1-2004 (``POSIX.1'') (XSI exten-
     sion).


HISTORY

     The functions endgrent(), getgrent(), getgrgid(), getgrnam(), and
     setgrent() appeared in Version 7 AT&T UNIX.  The functions setgrfile()
     and setgroupent() appeared in 4.3BSD-Reno.  The functions getgrgid_r()
     and getgrnam_r() appeared in NetBSD 3.0.


BUGS

     The functions getgrent(), getgrgid(), getgrnam(), setgroupent() and
     setgrent() leave their results in an internal static object and return a
     pointer to that object.  Subsequent calls to the same function will mod-
     ify the same object.

     The functions getgrent(), endgrent(), setgroupent(), and setgrent() are
     fairly useless in a networked environment and should be avoided, if pos-
     sible.  getgrent() makes no attempt to suppress duplicate information if
     multiple sources are specified in nsswitch.conf(5)

NetBSD 10.1                    February 7, 2018                    NetBSD 10.1