# Bash Parameter Subsitition

Variable	Description
$	Get default shell variables value
$	Set default shell variables value
${parameter:?"Error Message"}	Display an error message if parameter is not set
$	Find the length of the string
${var%pattern}	Remove from shortest rear (end) pattern
${var%%pattern}	Remove from longest rear (end) pattern
$	Substring
${var#pattern}	Remove from shortest front pattern
${var##pattern}	Remove from longest front pattern
${var/pattern/string}	Find and replace (only replace first occurrence)
${var//pattern/string}	Find and replace all occurrences
${!prefix*}	Expands to the names of variables whose names begin with prefix.
${var,} ${var,pattern}	Convert first character to lowercase.
${var,,} ${var,,pattern}	Convert all characters to lowercase.
${var^} ${var^pattern}	Convert first character to uppercase.
${var^^} ${var^^pattern}	Convert all character to uppercase.

# References