tarun28jain:

A couple items:

• Your read_line function isn't returning a file position, so write_log won't be able to seek to the correct location. Instead, you're returning the contents of a line. If it happens to be a number, then you may be changing a line pretty far away from where you intend!
• It looks like you're confusing file position (the index of the current byte in the file) with line number (how many lines have we read so far).
• If you fix these problems, you'll find that if your new text is a different length than the original line, you'll either leave garbage in your file, or overwrite some of the next line(s).

Typically, if you want to make an edit in the middle of the file, you'll want to rewrite the entire file, unless your substitution text has the same number of bytes as the text it's replacing. (Can be complicated, especially when Unicode is involved.)

I'd suggest doing it a bit more like:

open my $INF, '<', $filename;
open my $OUF, '>', $filename . ".new";

my @lines = <$INF>;
$lines[2] = "12345\n";

print $OUF @lines;
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However, reading the entire file into memory may be a problem, so you may want to process line-by-line instead.

...roboticus

When your only tool is a hammer, all problems look like your thumb.