# fclose

## 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



           fclose — close a stream
    


## SYNOPSIS



           #include <stdio.h>
    
           int fclose(FILE *_stream_);
    


## DESCRIPTION



           The functionality described on this reference page is aligned with
           the ISO C standard. Any conflict between the requirements
           described here and the ISO C standard is unintentional. This
           volume of POSIX.1‐2017 defers to the ISO C standard.
    
           The _fclose_() function shall cause the stream pointed to by _stream_
           to be flushed and the associated file to be closed. Any unwritten
           buffered data for the stream shall be written to the file; any
           unread buffered data shall be discarded. Whether or not the call
           succeeds, the stream shall be disassociated from the file and any
           buffer set by the _setbuf_() or _setvbuf_() function shall be
           disassociated from the stream. If the associated buffer was
           automatically allocated, it shall be deallocated.
    
           If the file is not already at EOF, and the file is one capable of
           seeking, the file offset of the underlying open file description
           shall be set to the file position of the stream if the stream is
           the active handle to the underlying file description.
    
           The _fclose_() function shall mark for update the last data
           modification and last file status change timestamps of the
           underlying file, if the stream was writable, and if buffered data
           remains that has not yet been written to the file. The _fclose_()
           function shall perform the equivalent of a _close_() on the file
           descriptor that is associated with the stream pointed to by
           _stream_.
    
           After the call to _fclose_(), any use of _stream_ results in undefined
           behavior.
    


## RETURN VALUE



           Upon successful completion, _fclose_() shall return 0; otherwise, it
           shall return EOF and set _errno_ to indicate the error.
    


## ERRORS



           The _fclose_() function shall fail if:
    
           **EAGAIN** The O_NONBLOCK flag is set for the file descriptor
                  underlying _stream_ and the thread would be delayed in the
                  write operation.
    
           **EBADF** The file descriptor underlying stream is not valid.
    
           **EFBIG** An attempt was made to write a file that exceeds the
                  maximum file size.
    
           **EFBIG** An attempt was made to write a file that exceeds the file
                  size limit of the process.
    
           **EFBIG** The file is a regular file and an attempt was made to write
                  at or beyond the offset maximum associated with the
                  corresponding stream.
    
           **EINTR** The _fclose_() function was interrupted by a signal.
    
           **EIO** The process is a member of a background process group
                  attempting to write to its controlling terminal, TOSTOP is
                  set, the calling thread is not blocking SIGTTOU, the
                  process is not ignoring SIGTTOU, and the process group of
                  the process is orphaned.  This error may also be returned
                  under implementation-defined conditions.
    
           **ENOMEM** The underlying stream was created by _open_memstream_() or
                  _open_wmemstream_() and insufficient memory is available.
    
           **ENOSPC** There was no free space remaining on the device containing
                  the file or in the buffer used by the _fmemopen_() function.
    
           **EPIPE** An attempt is made to write to a pipe or FIFO that is not
                  open for reading by any process. A SIGPIPE signal shall
                  also be sent to the thread.
    
           The _fclose_() function may fail if:
    
           **ENXIO** A request was made of a nonexistent device, or the request
                  was outside the capabilities of the device.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           Since after the call to _fclose_() any use of _stream_ results in
           undefined behavior, _fclose_() should not be used on _stdin_ , _stdout_ ,
           or _stderr_ except immediately before process termination (see the
           Base Definitions volume of POSIX.1‐2017, _Section 3.303_ , _Process_
           _Termination_), so as to avoid triggering undefined behavior in
           other standard interfaces that rely on these streams. If there are
           any _atexit_() handlers registered by the application, such a call
           to _fclose_() should not occur until the last handler is finishing.
           Once _fclose_() has been used to close _stdin_ , _stdout_ , or _stderr_ ,
           there is no standard way to reopen any of these streams.
    
           Use of _freopen_() to change _stdin_ , _stdout_ , or _stderr_ instead of
           closing them avoids the danger of a file unexpectedly being opened
           as one of the special file descriptors STDIN_FILENO,
           STDOUT_FILENO, or STDERR_FILENO at a later time in the
           application.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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