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
  37 #if USE_UNLOCKED_IO
  38 # include "unlocked-io.h"
  39 #endif
  40
  41 static const char *file_name;
  42
  43 /* Set the file name to be reported in the event an error is detected
  44    by close_stdout.  */
  45 void
  46 close_stdout_set_file_name (const char *file)
  47 {
  48   file_name = file;
  49 }
  50
  51 /* Close standard output, exiting with status 'exit_failure' on failure.
  52    If a program writes *anything* to stdout, that program should close
  53    stdout and make sure that it succeeds before exiting.  Otherwise,
  54    suppose that you go to the extreme of checking the return status
  55    of every function that does an explicit write to stdout.  The last
  56    printf can succeed in writing to the internal stream buffer, and yet
  57    the fclose(stdout) could still fail (due e.g., to a disk full error)
  58    when it tries to write out that buffered data.  Thus, you would be
  59    left with an incomplete output file and the offending program would
  60    exit successfully.  Even calling fflush is not always sufficient,
  61    since some file systems (NFS and CODA) buffer written/flushed data
  62    until an actual close call.
  63
  64    Besides, it's wasteful to check the return value from every call
  65    that writes to stdout -- just let the internal stream state record
  66    the failure.  That's what the ferror test is checking below.
  67
  68    It's important to detect such failures and exit nonzero because many
  69    tools (most notably `make' and other build-management systems) depend
  70    on being able to detect failure in other tools via their exit status.  */
  71
  72 void
  73 close_stdout (void)
  74 {
  75   bool prev_fail = ferror (stdout);
  76   bool none_pending = (0 == __fpending (stdout));
  77   bool fclose_fail = fclose (stdout);
  78
  79   if (prev_fail || fclose_fail)
  80     {
  81       int e = fclose_fail ? errno : 0;
  82       char const *write_error;
  83
  84       /* If ferror returned zero, no data remains to be flushed, and we'd
  85          otherwise fail with EBADF due to a failed fclose, then assume that
  86          it's ok to ignore the fclose failure.  That can happen when a
  87          program like cp is invoked like this `cp a b >&-' (i.e., with
  88          stdout closed) and doesn't generate any output (hence no previous
  89          error and nothing to be flushed).  */
  90       if (e == EBADF && !prev_fail && none_pending)
  91         return;
  92
  93       write_error = _("write error");
  94       if (file_name)
  95         error (exit_failure, e, "%s: %s", quotearg_colon (file_name),
  96                write_error);
  97       else
  98         error (exit_failure, e, "%s", write_error);
  99     }
 100 }