1/* Close standard output and standard error, exiting with a diagnostic on error.
2
3   Copyright (C) 1998-2002, 2004, 2006, 2008-2012 Free Software Foundation,
4   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 3 of the License, or
9   (at your option) 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, see <http://www.gnu.org/licenses/>.  */
18
19#include <config.h>
20
21#include "closeout.h"
22
23#include <errno.h>
24#include <stdbool.h>
25#include <stdio.h>
26#include <unistd.h>
27
28#include "gettext.h"
29#define _(msgid) gettext (msgid)
30
31#include "close-stream.h"
32#include "error.h"
33#include "exitfail.h"
34#include "quotearg.h"
35
36static const char *file_name;
37
38/* Set the file name to be reported in the event an error is detected
39   by close_stdout.  */
40void
41close_stdout_set_file_name (const char *file)
42{
43  file_name = file;
44}
45
46static bool ignore_EPIPE /* = false */;
47
48/* Specify the reaction to an EPIPE error during the closing of stdout:
49     - If ignore = true, it shall be ignored.
50     - If ignore = false, it shall evoke a diagnostic, along with a nonzero
51       exit status.
52   The default is ignore = false.
53
54   This setting matters only if the SIGPIPE signal is ignored (i.e. its
55   handler set to SIG_IGN) or blocked.  Only particular programs need to
56   temporarily ignore SIGPIPE.  If SIGPIPE is ignored or blocked because
57   it was ignored or blocked in the parent process when it created the
58   child process, it usually is a bug in the parent process: It is bad
59   practice to have SIGPIPE ignored or blocked while creating a child
60   process.
61
62   EPIPE occurs when writing to a pipe or socket that has no readers now,
63   when SIGPIPE is ignored or blocked.
64
65   The ignore = false setting is suitable for a scenario where it is normally
66   guaranteed that the pipe writer terminates before the pipe reader.  In
67   this case, an EPIPE is an indication of a premature termination of the
68   pipe reader and should lead to a diagnostic and a nonzero exit status.
69
70   The ignore = true setting is suitable for a scenario where you don't know
71   ahead of time whether the pipe writer or the pipe reader will terminate
72   first.  In this case, an EPIPE is an indication that the pipe writer can
73   stop doing useless write() calls; this is what close_stdout does anyway.
74   EPIPE is part of the normal pipe/socket shutdown protocol in this case,
75   and should not lead to a diagnostic message.  */
76
77void
78close_stdout_set_ignore_EPIPE (bool ignore)
79{
80  ignore_EPIPE = ignore;
81}
82
83/* Close standard output.  On error, issue a diagnostic and _exit
84   with status 'exit_failure'.
85
86   Also close standard error.  On error, _exit with status 'exit_failure'.
87
88   Since close_stdout is commonly registered via 'atexit', POSIX
89   and the C standard both say that it should not call 'exit',
90   because the behavior is undefined if 'exit' is called more than
91   once.  So it calls '_exit' instead of 'exit'.  If close_stdout
92   is registered via atexit before other functions are registered,
93   the other functions can act before this _exit is invoked.
94
95   Applications that use close_stdout should flush any streams
96   other than stdout and stderr before exiting, since the call to
97   _exit will bypass other buffer flushing.  Applications should
98   be flushing and closing other streams anyway, to check for I/O
99   errors.  Also, applications should not use tmpfile, since _exit
100   can bypass the removal of these files.
101
102   It's important to detect such failures and exit nonzero because many
103   tools (most notably 'make' and other build-management systems) depend
104   on being able to detect failure in other tools via their exit status.  */
105
106void
107close_stdout (void)
108{
109  if (close_stream (stdout) != 0
110      && !(ignore_EPIPE && errno == EPIPE))
111    {
112      char const *write_error = _("write error");
113      if (file_name)
114        error (0, errno, "%s: %s", quotearg_colon (file_name),
115               write_error);
116      else
117        error (0, errno, "%s", write_error);
118
119      _exit (exit_failure);
120    }
121
122   if (close_stream (stderr) != 0)
123     _exit (exit_failure);
124}
125