gnu/dist/gettext/gettext-tools/lib/fwriteerror.h

   1 /* Detect write error on a stream.
   2    Copyright (C) 2003, 2005 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2003.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 /* There are two approaches for detecting a write error on a stream opened
  20    for writing:
  21
  22      (a) Test the return value of every fwrite() or fprintf() call, and react
  23          immediately.
  24      (b) Just before fclose(), test the error indicator in the stream and
  25          the return value of the final fclose() call.
  26
  27    The benefit of (a) is that non file related errors (such that ENOMEM during
  28    fprintf) and temporary error conditions can be diagnosed accurately.
  29
  30    A theoretical benefit of (a) is also that, on POSIX systems, in the case of
  31    an ENOSPC error, errno is set and can be used by error() to provide a more
  32    accurate error message. But in practice, this benefit is not big because
  33    users can easily figure out by themselves why a file cannot be written to,
  34    and furthermore the function fwriteerror() can provide errno as well.
  35
  36    The big drawback of (a) is extensive error checking code: Every function
  37    which does stream output must return an error indicator.
  38
  39    This file provides support for (b).  */
  40
  41 #include <stdio.h>
  42
  43 /* Write out the not yet written buffered contents of the stream FP, close
  44    the stream FP, and test whether some error occurred on the stream FP.
  45    FP must be a stream opened for writing.
  46    Return 0 if no error occurred and fclose (fp) succeeded.
  47    Return -1 and set errno if there was an error.  The errno value will be 0
  48    if the cause of the error cannot be determined.
  49    For any given stream FP other than stdout, fwriteerror (FP) may only be
  50    called once.  */
  51 extern int fwriteerror (FILE *fp);