Execute shell script:
./script.sh bash script.sh source script.sh
Read user input:
read
Echo text to screen:
echo
Arithmetic operations:
let expr
Conditional statements:
if case
Loops:
for while
Array operations:
declare read -a
Check file/directory existence:
[file] -e [file] -d [file] -f
Check file permissions:
[file] -r [file] -w [file] -x
Check file type:
[file] -b [file] -c [file] -L [file] -S