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/* Close standard input, rewinding seekable stdin if necessary.
Copyright (C) 2007, 2009-2022 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
#include "closein.h"
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>
#include "gettext.h"
#define _(msgid) gettext (msgid)
#include "close-stream.h"
#include "closeout.h"
#include "error.h"
#include "exitfail.h"
#include "freadahead.h"
#include "quotearg.h"
static const char *file_name;
/* Set the file name to be reported in the event an error is detected
on stdin by close_stdin. See also close_stdout_set_file_name, if
an error is detected when closing stdout. */
void
close_stdin_set_file_name (const char *file)
{
file_name = file;
}
/* Close standard input, rewinding any unused input if stdin is
seekable. On error, issue a diagnostic and _exit with status
'exit_failure'. Then call close_stdout.
Most programs can get by with close_stdout. close_stdin is only
needed when a program wants to guarantee that partially read input
from seekable stdin is not consumed, for any subsequent clients.
For example, POSIX requires that these two commands behave alike:
(sed -ne 1q; cat) < file
tail -n +2 file
Since close_stdin is commonly registered via 'atexit', POSIX
and the C standard both say that it should not call 'exit',
because the behavior is undefined if 'exit' is called more than
once. So it calls '_exit' instead of 'exit'. If close_stdin
is registered via atexit before other functions are registered,
the other functions can act before this _exit is invoked.
Applications that use close_stdout should flush any streams other
than stdin, stdout, and stderr before exiting, since the call to
_exit will bypass other buffer flushing. Applications should be
flushing and closing other streams anyway, to check for I/O errors.
Also, applications should not use tmpfile, since _exit can bypass
the removal of these files.
It's important to detect such failures and exit nonzero because many
tools (most notably 'make' and other build-management systems) depend
on being able to detect failure in other tools via their exit status. */
void
close_stdin (void)
{
bool fail = false;
/* There is no need to flush stdin if we can determine quickly that stdin's
input buffer is empty; in this case we know that if stdin is seekable,
(fseeko (stdin, 0, SEEK_CUR), ftello (stdin))
== lseek (0, 0, SEEK_CUR). */
if (freadahead (stdin) > 0)
{
/* Only attempt flush if stdin is seekable, as fflush is entitled to
fail on non-seekable streams. */
if (fseeko (stdin, 0, SEEK_CUR) == 0 && fflush (stdin) != 0)
fail = true;
}
if (close_stream (stdin) != 0)
fail = true;
if (fail)
{
/* Report failure, but defer exit until after closing stdout,
since the failure report should still be flushed. */
char const *close_error = _("error closing file");
if (file_name)
error (0, errno, "%s: %s", quotearg_colon (file_name),
close_error);
else
error (0, errno, "%s", close_error);
}
close_stdout ();
if (fail)
_exit (exit_failure);
}
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