contrib/cvs-1.12/lib/closeout.c

   1 /* closeout.c - close standard output
   2
   3    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004 Free Software
   4    Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 #ifdef HAVE_CONFIG_H
  21 # include <config.h>
  22 #endif
  23
  24 #include "closeout.h"
  25
  26 #include <stdio.h>
  27 #include <stdbool.h>
  28 #include <errno.h>
  29
  30 #include "gettext.h"
  31 #define _(msgid) gettext (msgid)
  32
  33 #include "error.h"
  34 #include "exitfail.h"
  35 #include "quotearg.h"
  36 #include "__fpending.h"
  37
  38 #if USE_UNLOCKED_IO
  39 # include "unlocked-io.h"
  40 #endif
  41
  42 static const char *file_name;
  43
  44 /* Set the file name to be reported in the event an error is detected
  45    by close_stdout.  */
  46 void
  47 close_stdout_set_file_name (const char *file)
  48 {
  49   file_name = file;
  50 }
  51
  52 /* Close standard output, exiting with status 'exit_failure' on failure.
  53    If a program writes *anything* to stdout, that program should close
  54    stdout and make sure that it succeeds before exiting.  Otherwise,
  55    suppose that you go to the extreme of checking the return status
  56    of every function that does an explicit write to stdout.  The last
  57    printf can succeed in writing to the internal stream buffer, and yet
  58    the fclose(stdout) could still fail (due e.g., to a disk full error)
  59    when it tries to write out that buffered data.  Thus, you would be
  60    left with an incomplete output file and the offending program would
  61    exit successfully.  Even calling fflush is not always sufficient,
  62    since some file systems (NFS and CODA) buffer written/flushed data
  63    until an actual close call.
  64
  65    Besides, it's wasteful to check the return value from every call
  66    that writes to stdout -- just let the internal stream state record
  67    the failure.  That's what the ferror test is checking below.
  68
  69    It's important to detect such failures and exit nonzero because many
  70    tools (most notably `make' and other build-management systems) depend
  71    on being able to detect failure in other tools via their exit status.  */
  72
  73 void
  74 close_stdout (void)
  75 {
  76   bool prev_fail = ferror (stdout);
  77   bool none_pending = (0 == __fpending (stdout));
  78   bool fclose_fail = fclose (stdout);
  79
  80   if (prev_fail || fclose_fail)
  81     {
  82       int e = fclose_fail ? errno : 0;
  83       char const *write_error;
  84
  85       /* If ferror returned zero, no data remains to be flushed, and we'd
  86          otherwise fail with EBADF due to a failed fclose, then assume that
  87          it's ok to ignore the fclose failure.  That can happen when a
  88          program like cp is invoked like this `cp a b >&-' (i.e., with
  89          stdout closed) and doesn't generate any output (hence no previous
  90          error and nothing to be flushed).  */
  91       if (e == EBADF && !prev_fail && none_pending)
  92         return;
  93
  94       write_error = _("write error");
  95       if (file_name)
  96         error (exit_failure, e, "%s: %s", quotearg_colon (file_name),
  97                write_error);
  98       else
  99         error (exit_failure, e, "%s", write_error);
 100     }
 101 }