Why does this code work correctly, while the other version of the same condition doesn't?
if grep -q string file; then
echo found
else
echo not found
fi
This doesn't work:
if [ ! `grep -q string file` ]; then
echo not found
else
echo found
fi
`grep -q string file`, in backticks (or inside $(...), which is preferable), will be replaced by the output of grep. This will be an empty string since -q is used.
To negate a test, just insert ! before it:
if ! grep -q pattern file; then
echo not found
else
echo found
fi
If you truly want to search for a string (rather than a regular expression), then you should use -F with grep as well.
-qdoes, or are you just blindly using it because you've seen others use it?