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FFLUSH(P)		   POSIX Programmer's Manual		     FFLUSH(P)

NAME
       fflush - flush a stream

SYNOPSIS
       #include <stdio.h>

       int fflush(FILE *stream);

DESCRIPTION
       If  stream  points to an output stream or an update stream in which the
       most recent operation was not input, fflush() shall cause any unwritten
       data for that stream to be written to the file,	  and the st_ctime and
       st_mtime fields of the underlying file shall be marked for update.

       If stream is a null  pointer,  fflush()	shall  perform	this  flushing
       action on all streams for which the behavior is defined above.

RETURN VALUE
       Upon  successful	 completion,  fflush()	shall  return 0; otherwise, it
       shall set the error indicator for the  stream,  return  EOF,   and  set
       errno to indicate the error.

ERRORS
       The fflush() function shall fail if:

       EAGAIN The  O_NONBLOCK  flag  is set for the file descriptor underlying
	      stream and the process 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 process'
	      file size limit.

       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 fflush() 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 process
	      is neither ignoring nor blocking SIGTTOU, and the process	 group
	      of  the  process	is  orphaned.  This error may also be returned
	      under implementation-defined conditions.

       ENOSPC There was no free space remaining on the device  containing  the
	      file.

       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 fflush() 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
   Sending Prompts to Standard Output
       The following example uses printf() calls to print a series of  prompts
       for  information	 the user must enter from standard input. The fflush()
       calls force the output to standard output.  The	fflush()  function  is
       used because standard output is usually buffered and the prompt may not
       immediately be printed on the output or terminal. The gets() calls read
       strings from standard input and place the results in variables, for use
       later in the program.

	      #include <stdio.h>
	      ...
	      char user[100];
	      char oldpasswd[100];
	      char newpasswd[100];
	      ...
	      printf("User name: ");
	      fflush(stdout);
	      gets(user);

	      printf("Old password: ");
	      fflush(stdout);
	      gets(oldpasswd);

	      printf("New password: ");
	      fflush(stdout);
	      gets(newpasswd);
	      ...

APPLICATION USAGE
       None.

RATIONALE
       Data buffered by the system may make determining the  validity  of  the
       position	 of  the  current file descriptor impractical. Thus, enforcing
       the repositioning of the file descriptor after fflush() on streams open
       for read() is not mandated by IEEE Std 1003.1-2001.

FUTURE DIRECTIONS
       None.

SEE ALSO
       getrlimit()   ,	 ulimit()   ,	the   Base   Definitions   volume   of
       IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),	The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the	referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group		     2003			     FFLUSH(P)
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