Editing text files programmatically
It can often be useful to edit text files without manual intervention, in a program.
The tools sed and awk are particularly useful for this.
Editing a line
/bin/sed -i "s/${PATTERN}/${REPLACEMENT}/" $MYFILE
s = substitute
Deleting a block of text
/bin/sed -i "/^;${MARK_START}/,/^;${MARK_END}/d" $MYFILE
d = delete