Line data    Source code

       1             : /* Close standard input, rewinding seekable stdin if necessary.
       2             : 
       3             :    Copyright (C) 2007 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
      43           0 : close_stdin_set_file_name (const char *file)
      44             : {
      45           0 :   file_name = file;
      46           0 : }
      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 1 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
      79         666 : close_stdin (void)
      80             : {
      81         666 :   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) == lseek (0, 0, SEEK_CUR).  */
      86         666 :   if (freadahead (stdin) > 0)
      87             :     {
      88             :       /* Only attempt flush if stdin is seekable, as fflush is entitled to
      89             :          fail on non-seekable streams.  */
      90          12 :       if (fseeko (stdin, 0, SEEK_CUR) == 0 && fflush (stdin) != 0)
      91           0 :         fail = true;
      92             :     }
      93         666 :   if (close_stream (stdin) != 0)
      94           0 :     fail = true;
      95         666 :   if (fail)
      96             :     {
      97             :       /* Report failure, but defer exit until after closing stdout,
      98             :          since the failure report should still be flushed.  */
      99           0 :       char const *close_error = _("error closing file");
     100           0 :       if (file_name)
     101           0 :         error (0, errno, "%s: %s", quotearg_colon (file_name),
     102             :                close_error);
     103             :       else
     104           0 :         error (0, errno, "%s", close_error);
     105             :     }
     106             : 
     107         666 :   close_stdout ();
     108             : 
     109         666 :   if (fail)
     110           0 :     _exit (exit_failure);
     111         666 : }