in reply to
quick way to add a line to a file, if it's not already present (automating tweaking of /etc/ld.so.conf for installing Image::Magick)
As you mentioned, TIMTOWTDI. I think I'd rather stick with doing more with bash since that's what most of the script is in. If you want a one-liner you could always separate the parts with a ; :-). Something like:
if grep -v -q 'the_line' ld.so.conf; then echo 'the_line' >> ld.so.con
You probably already thought of this, but I figured I'd document it for posterity's sake.