writing in the middle of a file

[amduser]

Hi,

I need to write s string in the middle of the file.

I can't seem to do this the C++ way ( using the file pointer ) as ftell seems to go haywire.

Whatever I fwrite() seems to be appended at the end of the file.

If if open the file on the 'w' mode , everything gets truncated.

Anyone have a solution for this ? I need to write append in between the file without doing a file overwrite.

Thanks ,

p.s. When I open a file in the 'a' or 'a+' mode , a ftell() displays the file pointer at 0 and not at the end of the file. Any idea why this happens ?

[Installer]

When I open a file in the 'a' or 'a+' mode , a ftell() displays the file pointer at 0 and not at the end of the file. Any idea why this happens ?

The manual, of all places, says this about that:

ftell() gives undefined results for append-only streams (opened with "a" flag).

And it says the same about "fseek()":

fseek() gives also undefined results for append-only streams (opened with "a" flag).

If you open with "r+" then set the position with "fseek($n)" you can write to that position. Unfortunately, that overwrites the next strlen characters, instead of pushing everything back.

So...read the first n-1 characters into a string, and the rest into another string, then concatenate, with your string to insert between the two.

function fwrite_to_offset($file, $str, $offset)
{
    $contents = file_get_contents($file);
    $part_1 = substr($contents, 0, $offset);
    $part_2 = substr($contents, $offset);
    $new = $part_1 . $str . $part_2;
    $fp = fopen($file, 'w');
    fwrite($fp, $new);
    fclose($fp);
}

(Add your own error checking.)