Bash shell expansion- Quick reference

bash_variables.org

Operator	Meaning
${parameter#pattern}	Remove the shortest string that matches the pattern if it’s at the start of the value
${parameter##pattern}	Remove the longest string that matches the pattern it it’s at the start of value
${parameter%pattern}	Remove the shortest string that matches the pattern if it’s at the end of the value
${parameter%%pattern}	Remove the longest string that matches the pattern it it’s at the end of value
${parameter/pattern/replacement}	Replace the first string that matches the pattern with the replacement
${parameter//pattern/replacement}	Replace each string that matches the /pattern/with the replacement
${parameter/#pattern/replacement}	Replace the string that matches the pattern at the beginning of the value with the replacement
${parameter/%pattern/replacement}	Replace the string that matches the pattern at the end of the value with the replacement
${#parameter}	Expand the length of the value (in bytes)
${parameter:start[:length]}	Expand a part of the value, starting at start, length bytes long
=${parameter[^|^^|,|,,][pattern]}	Expand the transformed value, either upper-casing or lower-casing the first or all characters that match the pattern. You can omit the pattern to match any character

Src: http://guide.bash.academy/variables.html