http://tldp.org/LDP/abs/html/

echo ${PATH#*:}       # Parameter substitution, not a comment.
echo $(( 2#101011 ))  # Base conversion, not a comment.
echo ${param1:-DEFAULT}
echo "whatever" | cat -
file -
let "z = 5 % 3"
echo ~+
a="23456"; echo ${a/23/BB}
echo $(ls -l)
type '['
type '[['
echo $((RANDOM%16))
str="123abc"; echo ${#str}; expr length $str; expr "$str" : '.*'
expr match "$string" '$substring'
expr "$string" : '$substring'
echo ${str:2:3}
echo ${*:2}; echo ${@:2}
expr match "$string" '\($substring\)'
expr "$string" : '\($substring\)'
${string#substring}
${string##substring}
${string%substring}
${string%%substring}
${string/substring/replacement}
${string//substring/replacement}
${string/#substring/replacement}
${string/%substring/replacement}
echo ${parameter-default}; ${parameter:-default}
${parameter=default}; ${parameter:=default}
${parameter?err_msg}, ${parameter:?err_msg}
${var#Pattern}, ${var##Pattern}
${var%Pattern}, ${var%%Pattern}