I agree with basically all of this. A few more:
The order of commandline args shouldn't matter.
Env vars are better at passing key/value inputs than commandline arguments are.
Process-substitution can often be used to avoid intermediate files, e.g. `diff some-file temp; diff some-file temp`
If you're making intermediate files, make a temp dir and `cd` into that
- Delete temp dirs using an exit trap (more reliable than e.g. putting it at the end of the script)
- It may be useful to copy `$PWD` into a variable before changing directory
Be aware of subshells and scope. For example, if we pipe into a loop, the loop is running in a sub-shell, and hence its state will be discarded afterwards:
LINE_COUNT=0
some command | while read -r X
do
# This runs in a sub-shell; it inherits the initial LINE_COUNT from the parent,
# but any mutations are limited to the sub-shell, will be discarded
(( LINE_COUNT++ ))
done
echo "$LINE_COUNT" # This will echo '0', since the incremented version was discarded
Process-substitution can help with this, e.g.
LINE_COUNT=0
while read -r X
do
# This runs in the main shell; its increments will remain afterwards
(( LINE_COUNT++ ))
done