I need this all the time. Thank you so much

[ condition ] is an external program naned "[" which is a symbolic link to test.

[[ condition ]] is a bash condition

fantastic. great work

Thanks - great cheat sheet. Perhaps include some handy filesystem 1-liner examples?

for F in *.txt; do echo "$F" >> files.list; done

Or, the more capable, recursive:

IFS=$'\n'; for F in `find . -type f -name "*.txt"`; do echo "$F"; echo "Second action $F"; done

Simpler, recursive, single action:

find . -type f -name "*.txt"` -exec echo '{}' \;

I know "find" isn't a bash feature - but it sure is a handy command to be aware of.