insert text to a file using command line
 

I need to be able to edit a file from the commend line as I intend to script this operation, the file is called menu.lst

The original is as below

I need to add acpi=force to two lines as below

Any ideas?

Test it first without the "-i" flag

The most straightforward method to edit a file using a command is by means of the sed editor. If you're already familiar with it, take in mind you can edit the file in place using the option -i. But always do a backup copy of your original file, until you're sure the result is exactly as your expectations. sed permits to do this automatically, just by adding a suffix to the option -i, e.g.
will create a backup copy named file.bck, before editing file. Maybe you already know all of this, but it's worth to mention for safety.

Regarding your question, using sed you can just address the lines containing the keyword "kernel" at the beginning and add " acpi=force" at the end. For example:
Don't forget the space before "apci".

Edit: too late... sorry for redundancy. Pixellany, I envy your ability to be clear and succinct... :)

Slight modification

Because i don't know whether memtest will handle the acpi=force

He he.. that's right! :)