1 /* Close standard input, rewinding seekable stdin if necessary.
3 Copyright (C) 2007 Free Software Foundation, Inc.
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 2, or (at your option)
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.
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software Foundation,
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
29 #define _(msgid) gettext (msgid)
31 #include "close-stream.h"
35 #include "freadahead.h"
38 static const char *file_name;
40 /* Set the file name to be reported in the event an error is detected
41 on stdin by close_stdin. See also close_stdout_set_file_name, if
42 an error is detected when closing stdout. */
44 close_stdin_set_file_name (const char *file)
49 /* Close standard input, rewinding any unused input if stdin is
50 seekable. On error, issue a diagnostic and _exit with status
51 'exit_failure'. Then call close_stdout.
53 Most programs can get by with close_stdout. close_stdin is only
54 needed when a program wants to guarantee that partially read input
55 from seekable stdin is not consumed, for any subsequent clients.
56 For example, POSIX requires that these two commands behave alike:
58 (sed -ne 1q; cat) < file
61 Since close_stdin is commonly registered via 'atexit', POSIX
62 and the C standard both say that it should not call 'exit',
63 because the behavior is undefined if 'exit' is called more than
64 once. So it calls '_exit' instead of 'exit'. If close_stdin
65 is registered via atexit before other functions are registered,
66 the other functions can act before this _exit is invoked.
68 Applications that use close_stdout should flush any streams other
69 than stdin, stdout, and stderr before exiting, since the call to
70 _exit will bypass other buffer flushing. Applications should be
71 flushing and closing other streams anyway, to check for I/O errors.
72 Also, applications should not use tmpfile, since _exit can bypass
73 the removal of these files.
75 It's important to detect such failures and exit nonzero because many
76 tools (most notably `make' and other build-management systems) depend
77 on being able to detect failure in other tools via their exit status. */
84 /* There is no need to flush stdin if we can determine quickly that stdin's
85 input buffer is empty; in this case we know that if stdin is seekable,
86 fseeko (stdin, 0, SEEK_CUR) == lseek (0, 0, SEEK_CUR). */
87 if (freadahead (stdin) > 0)
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)
94 if (close_stream (stdin) != 0)
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");
102 error (0, errno, "%s: %s", quotearg_colon (file_name),
105 error (0, errno, "%s", close_error);
111 _exit (exit_failure);