closein: correct comments

[gnulib.git] / lib / closein.c

diff --git a/lib/closein.c b/lib/closein.c
index 1aade1d..2a652f4 100644 (file)
--- a/lib/closein.c
+++ b/lib/closein.c
@@ -1,11 +1,11 @@
 /* Close standard input, rewinding seekable stdin if necessary.
 
-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007, 2009-2011 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   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 2, or (at your option)
-   any later version.
+   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
@@ -13,13 +13,11 @@
    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, write to the Free Software Foundation,
-   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include <config.h>
 
 #include "closein.h"
-#include "closeout.h"
 
 #include <errno.h>
 #include <stdbool.h>
@@ -30,8 +28,10 @@
 #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;
@@ -55,7 +55,7 @@ close_stdin_set_file_name (const char *file)
    For example, POSIX requires that these two commands behave alike:
 
      (sed -ne 1q; cat) < file
-     tail -n 1 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',
@@ -79,18 +79,30 @@ 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);
+        error (0, errno, "%s: %s", quotearg_colon (file_name),
+               close_error);
       else
-       error (0, errno, "%s", close_error);
-
-      /* Defer failure until after closing stdout, since the output
-        can still usefully be flushed.  */
-      fail = true;
+        error (0, errno, "%s", close_error);
     }
 
   close_stdout ();