Bug#254475: The bug is still there in 0.97-21

[Friedemann Baitinger]

sorry for the noise ... but I have to report additional findings as the 
patch above really has some side-effects.

The previous version of my patch opened the /boot/grub/defaults file in 
"r+" mode so I could read the initial values, do a "rewind(fp)" and 
write the new values. Unfortunately the "grub-reboot" script keeps to 
append new comments and disclaimer lines, effectively making the file 
grow and grow.

So the only thing that really works here is to open the file read-only, 
read the initial values, then close it and reopen it in "w" mode which 
truncates it to zero before we write to it. Now we write the new "x:y" 
values and let the script to its job of adding comment lines and 
disclaimers.

Also, the original code added a newline where "grub-set-default" didn't 
have one. Not a big deal, shouldn't change the functionality but it 
isn't the same layout as before anymore.

To make a long story short, here is a new patch which *should* do the 
job now as expected:

--- builtins.c.orig     2007-01-28 16:46:18.000000000 +0100
+++ builtins.c  2007-01-28 21:25:29.000000000 +0100
@@ -3574,16 +3574,17 @@
    default_file[i] = 0;
    grub_strncat (default_file + i, "default", DEFAULT_FILE_BUFLEN - i);

-  if(!(fp = fopen(default_file,"w")))
+  if(!(fp = fopen(default_file,"r")))
      {
        errnum = ERR_READ;
        goto fail;
      }

-  read(&line, -1);
-
+  fgets(line, bytes, fp);
+  fclose(fp);
+
    sscanf(line, "%d:%d", &curr_prev_default, &curr_default);
-
+
    if(curr_default != -1)
      new_prev_default = curr_default;
    else
@@ -3595,10 +3596,16 @@
      }

    if(once_only)
-    sprintf(buf, "%d:%d\n", new_prev_default, new_default);
+    sprintf(buf, "%d:%d", new_prev_default, new_default);
    else
-    sprintf(buf, "%d\n", new_default);
-
+    sprintf(buf, "%d", new_default);
+
+  if(!(fp = fopen(default_file,"w")))
+    {
+      errnum = ERR_READ;
+      goto fail;
+    }
+
    fprintf(fp, buf);

  fail:



-- 
Friedemann Baitinger   baiti at web.de