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 #include <sys/cdefs.h>
20 __RCSID("$NetBSD: closeout.c,v 1.2 2016/05/17 14:00:09 christos Exp $");
21
22
23 #ifdef HAVE_CONFIG_H
24 # include <config.h>
25 #endif
26
27 #include "closeout.h"
28
29 #include <stdio.h>
30 #include <stdbool.h>
31 #include <errno.h>
32
33 #include "gettext.h"
34 #define _(msgid) gettext (msgid)
35
36 #include "error.h"
37 #include "exitfail.h"
38 #include "quotearg.h"
39 #include "__fpending.h"
40
41 #if USE_UNLOCKED_IO
42 # include "unlocked-io.h"
43 #endif
44
45 static const char *file_name;
46
47 /* Set the file name to be reported in the event an error is detected
48 by close_stdout. */
49 void
close_stdout_set_file_name(const char * file)50 close_stdout_set_file_name (const char *file)
51 {
52 file_name = file;
53 }
54
55 /* Close standard output, exiting with status 'exit_failure' on failure.
56 If a program writes *anything* to stdout, that program should close
57 stdout and make sure that it succeeds before exiting. Otherwise,
58 suppose that you go to the extreme of checking the return status
59 of every function that does an explicit write to stdout. The last
60 printf can succeed in writing to the internal stream buffer, and yet
61 the fclose(stdout) could still fail (due e.g., to a disk full error)
62 when it tries to write out that buffered data. Thus, you would be
63 left with an incomplete output file and the offending program would
64 exit successfully. Even calling fflush is not always sufficient,
65 since some file systems (NFS and CODA) buffer written/flushed data
66 until an actual close call.
67
68 Besides, it's wasteful to check the return value from every call
69 that writes to stdout -- just let the internal stream state record
70 the failure. That's what the ferror test is checking below.
71
72 It's important to detect such failures and exit nonzero because many
73 tools (most notably `make' and other build-management systems) depend
74 on being able to detect failure in other tools via their exit status. */
75
76 void
close_stdout(void)77 close_stdout (void)
78 {
79 bool prev_fail = ferror (stdout);
80 bool none_pending = (0 == __fpending (stdout));
81 bool fclose_fail = fclose (stdout);
82
83 if (prev_fail || fclose_fail)
84 {
85 int e = fclose_fail ? errno : 0;
86 char const *write_error;
87
88 /* If ferror returned zero, no data remains to be flushed, and we'd
89 otherwise fail with EBADF due to a failed fclose, then assume that
90 it's ok to ignore the fclose failure. That can happen when a
91 program like cp is invoked like this `cp a b >&-' (i.e., with
92 stdout closed) and doesn't generate any output (hence no previous
93 error and nothing to be flushed). */
94 if (e == EBADF && !prev_fail && none_pending)
95 return;
96
97 write_error = _("write error");
98 if (file_name)
99 error (exit_failure, e, "%s: %s", quotearg_colon (file_name),
100 write_error);
101 else
102 error (exit_failure, e, "%s", write_error);
103 }
104 }
105