1 /* Close standard input, rewinding seekable stdin if necessary.
2
3 Copyright (C) 2007, 2009-2014 Free Software Foundation, Inc.
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 3 of the License, or
8 (at your option) 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, see <http://www.gnu.org/licenses/>. */
17
18 #include <config.h>
19
20 #include "closein.h"
21
22 #include <errno.h>
23 #include <stdbool.h>
24 #include <stdio.h>
25 #include <unistd.h>
26
27 #include "gettext.h"
28 #define _(msgid) gettext (msgid)
29
30 #include "close-stream.h"
31 #include "closeout.h"
32 #include "error.h"
33 #include "exitfail.h"
34 #include "freadahead.h"
35 #include "quotearg.h"
36
37 static const char *file_name;
38
39 /* Set the file name to be reported in the event an error is detected
40 on stdin by close_stdin. See also close_stdout_set_file_name, if
41 an error is detected when closing stdout. */
42 void
close_stdin_set_file_name(const char * file)43 close_stdin_set_file_name (const char *file)
44 {
45 file_name = file;
46 }
47
48 /* Close standard input, rewinding any unused input if stdin is
49 seekable. On error, issue a diagnostic and _exit with status
50 'exit_failure'. Then call close_stdout.
51
52 Most programs can get by with close_stdout. close_stdin is only
53 needed when a program wants to guarantee that partially read input
54 from seekable stdin is not consumed, for any subsequent clients.
55 For example, POSIX requires that these two commands behave alike:
56
57 (sed -ne 1q; cat) < file
58 tail -n +2 file
59
60 Since close_stdin is commonly registered via 'atexit', POSIX
61 and the C standard both say that it should not call 'exit',
62 because the behavior is undefined if 'exit' is called more than
63 once. So it calls '_exit' instead of 'exit'. If close_stdin
64 is registered via atexit before other functions are registered,
65 the other functions can act before this _exit is invoked.
66
67 Applications that use close_stdout should flush any streams other
68 than stdin, stdout, and stderr before exiting, since the call to
69 _exit will bypass other buffer flushing. Applications should be
70 flushing and closing other streams anyway, to check for I/O errors.
71 Also, applications should not use tmpfile, since _exit can bypass
72 the removal of these files.
73
74 It's important to detect such failures and exit nonzero because many
75 tools (most notably 'make' and other build-management systems) depend
76 on being able to detect failure in other tools via their exit status. */
77
78 void
close_stdin(void)79 close_stdin (void)
80 {
81 bool fail = false;
82
83 /* There is no need to flush stdin if we can determine quickly that stdin's
84 input buffer is empty; in this case we know that if stdin is seekable,
85 (fseeko (stdin, 0, SEEK_CUR), ftello (stdin))
86 == lseek (0, 0, SEEK_CUR). */
87 if (freadahead (stdin) > 0)
88 {
89 /* Only attempt flush if stdin is seekable, as fflush is entitled to
90 fail on non-seekable streams. */
91 if (fseeko (stdin, 0, SEEK_CUR) == 0 && fflush (stdin) != 0)
92 fail = true;
93 }
94 if (close_stream (stdin) != 0)
95 fail = true;
96 if (fail)
97 {
98 /* Report failure, but defer exit until after closing stdout,
99 since the failure report should still be flushed. */
100 char const *close_error = _("error closing file");
101 if (file_name)
102 error (0, errno, "%s: %s", quotearg_colon (file_name),
103 close_error);
104 else
105 error (0, errno, "%s", close_error);
106 }
107
108 close_stdout ();
109
110 if (fail)
111 _exit (exit_failure);
112 }
113