GETGRENT(3)            FreeBSD Library Functions Manual            GETGRENT(3)

NAME
     getgrent, getgrent_r, getgrnam, getgrnam_r, getgrgid, getgrgid_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 bufsize,
         struct group **result);

     struct group *
     getgrnam(const char *name);

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

     struct group *
     getgrgid(gid_t gid);

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

     int
     setgroupent(int stayopen);

     void
     setgrent(void);

     void
     endgrent(void);

DESCRIPTION
     These functions operate on the group database file /etc/group 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 gids 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.

     The functions getgrent_r(), getgrnam_r(), and getgrgid_r() are thread-
     safe versions of getgrent(), getgrnam(), and getgrgid(), respectively.
     The caller must provide storage for the results of the search in the grp,
     buffer, bufsize, and result arguments.  When these functions are
     successful, the grp argument will be filled-in, and a pointer to that
     argument will be stored in result.  If an entry is not found or an error
     occurs, result will be set to NULL.

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

     The setgroupent() function opens the file, or rewinds it if it is already
     open.  If stayopen is non-zero, file descriptors are left open,
     significantly speeding functions subsequent calls.  This functionality is
     unnecessary for getgrent() as it does not 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 identical to setgroupent() with an argument of
     zero.

     The endgrent() function closes any open files.

RETURN VALUES
     The functions getgrent(), getgrnam(), and getgrgid(), return a pointer to
     a group structure on success or NULL if the entry is not found or if an
     error occurs.  If an error does occur, errno will be set.  Note that
     programs must explicitly set errno to zero before calling any of these
     functions if they need to distinguish between a non-existent entry and an
     error.  The functions getgrent_r(), getgrnam_r(), and getgrgid_r() return
     0 if no error occurred, or an error number to indicate failure.  It is
     not an error if a matching entry is not found.  (Thus, if result is set
     to NULL and the return value is 0, no matching entry exists.)

     The function setgroupent() returns the value 1 if successful, otherwise
     the value 0 is returned.  The functions endgrent(), setgrent() and
     setgrfile() have no return value.

FILES
     /etc/group  group database file

COMPATIBILITY
     The historic function setgrfile(), which allowed the specification of
     alternate password databases, has been deprecated and is no longer
     available.

SEE ALSO
     getpwent(3), group(5), nsswitch.conf(5), yp(8)

STANDARDS
     The getgrent(), getgrnam(), getgrnam_r(), getgrgid(), getgrgid_r() and
     endgrent() functions conform to ISO/IEC 9945-1:1996 ("POSIX.1").  The
     setgrent() function differs from that standard in that its return type is
     int rather than void.

HISTORY
     The functions endgrent(), getgrent(), getgrnam(), getgrgid(), and
     setgrent() appeared in Version 7 AT&T UNIX.  The functions setgrfile()
     and setgroupent() appeared in 4.3BSD-Reno.  The functions getgrent_r(),
     getgrnam_r(), and getgrgid_r() appeared in FreeBSD 5.1.

BUGS
     The functions getgrent(), getgrnam(), getgrgid(), 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
     modify the same object.

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

FreeBSD 13.1-RELEASE-p6          July 31, 2016         FreeBSD 13.1-RELEASE-p6