ZLB

search recessively across folders for the presence of text string in files:

 grep -rHn --color -A 1 -B 1 textToSearchHere ./ 

list the type of files in a directory. Usually quite useful information:

 file * 

go to the previous working directory:

cd -

also, bash has built in a stack for directories:

popdir

pushdir

Search the bash command history:

ctrl-r

List the bash command history:

history

then type !512 for command number 512.