# endgrent

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           endgrent, getgrent, setgrent — group database entry functions
    


## SYNOPSIS



           #include <grp.h>
    
           void endgrent(void);
           struct group *getgrent(void);
           void setgrent(void);
    


## DESCRIPTION



           The _getgrent_() function shall return a pointer to a structure
           containing the broken-out fields of an entry in the group
           database. If the group database is not already open, _getgrent_()
           shall open it and return a pointer to a **group** structure containing
           the first entry in the database. Thereafter, it shall return a
           pointer to a **group** structure containing the next **group** structure
           in the group database, so successive calls may be used to search
           the entire database.
    
           An implementation that provides extended security controls may
           impose further implementation-defined restrictions on accessing
           the group database. In particular, the system may deny the
           existence of some or all of the group database entries associated
           with groups other than those groups associated with the caller and
           may omit users other than the caller from the list of members of
           groups in database entries that are returned.
    
           The _setgrent_() function shall rewind the group database so that
           the next _getgrent_() call returns the first entry, allowing
           repeated searches.
    
           The _endgrent_() function shall close the group database.
    
           The _setgrent_() and _endgrent_() functions shall not change the
           setting of _errno_ if successful.
    
           On error, the _setgrent_() and _endgrent_() functions shall set _errno_
           to indicate the error.
    
           Since no value is returned by the _setgrent_() and _endgrent_()
           functions, an application wishing to check for error situations
           should set _errno_ to 0, then call the function, then check _errno_.
    
           These functions need not be thread-safe.
    


## RETURN VALUE



           On successful completion, _getgrent_() shall return a pointer to a
           **group** structure. On end-of-file, _getgrent_() shall return a null
           pointer and shall not change the setting of _errno_.  On error,
           _getgrent_() shall return a null pointer and _errno_ shall be set to
           indicate the error.
    
           The application shall not modify the structure to which the return
           value points, nor any storage areas pointed to by pointers within
           the structure. The returned pointer, and pointers within the
           structure, might be invalidated or the structure or the storage
           areas might be overwritten by a subsequent call to _getgrgid_(),
           _getgrnam_(), or _getgrent_().  The returned pointer, and pointers
           within the structure, might also be invalidated if the calling
           thread is terminated.
    


## ERRORS



           These functions may fail if:
    
           **EINTR** A signal was caught during the operation.
    
           **EIO** An I/O error has occurred.
    
           In addition, the _getgrent_() and _setgrent_() functions may fail if:
    
           **EMFILE** All file descriptors available to the process are currently
                  open.
    
           **ENFILE** The maximum allowable number of files is currently open in
                  the system.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           These functions are provided due to their historical usage.
           Applications should avoid dependencies on fields in the group
           database, whether the database is a single file, or where in the
           file system name space the database resides. Applications should
           use _getgrnam_() and _getgrgid_() whenever possible because it avoids
           these dependencies.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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