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GETGRENT(3)              BSD Library Functions Manual              GETGRENT(3)

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

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <grp.h>

     void
     endgrent(void);

     struct group *
     getgrent(void);

     struct group *
     getgrgid(gid_t gid);

     int
     getgrgid_r(gid_t gid, 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);

     void
     setgrent(void);

     int
     setgroupent(int stayopen);

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 */
                   int     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.  Iden-tical Identical
     tical group names or group ids may result in undefined behavior.

     All of these routines are thread-safe.  The getgrent(), getgrgid(), and getgrnam() routines return a
     pointer to a result managed by the system library in a thread-specific data structure.  Every thread
     has space for a pointer to a struct group and allocates its own storage for the result.  Neither previ-ously previously
     ously returned values in memory nor a previously returned pointer value should be used by a thread
     after calling any one of these three routines.  Memory allocated by a thread is automatically released
     on subsequent calls by the same thread to any of these three routines, and when the thread exits.

     The functions getgrgid_r() and getgrnam_r() take additional arguments which supply storage space for
     the returned result.  The grp parameter is a pointer to a struct group, which must be allocated by the
     caller.  The buffer parameter is a pointer to a block of memory with a size specified by bufsize.  This
     buffer is used to hold the values which are pointed to by values filled in the grp structure.  Zero is
     returned on success.  If insufficient memory is supplied, these routines return ERANGE.

     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 routines 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, nonzero,
     zero, file descriptors are left open, significantly speeding functions' subsequent calls.  This func-tionality functionality
     tionality is unnecessary 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 identical to setgroupent() with an argument of zero.

     The endgrent() function closes any open files.

RETURN VALUES
     The functions getgrent(), getgrgid(), and getgrnam() each return a pointer to the group entry if suc-cessful; successful;
     cessful; if end-of-file is reached or an error occurs, a null pointer is returned.  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

LEGACY SYNOPSIS
     #include <grp.h>

     int
     setgrent(void);

     The function setgrent() returns the value 1 if successful; otherwise, the value 0 is returned.

SEE ALSO
     getpwent(3), yp(8), group(5)

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.

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

BUGS
     The functions getgrent(), getgrnam(), and getgrgid(), leave their results in internal thread-specific
     memory and return a pointer to that object.  Subsequent calls to any of these three routines by the
     same thread will release the object and return a new pointer value.

BSD                           September 29, 1994                           BSD