Linux CLI 65 🐧 Parameter expansion in shell scripts

a - what is parameter expasion in shell scripts part 1
Parameter expansion in a shell script allows you to manipulate variable values in various ways...
such as substring extraction, default value assignment, and pattern replacement.
common parameter expansions:
1. Substring Extraction:
 ${variable:position} → Extracts the substring from the specified position to the end.
${variable:position:length} → Extracts a substring of the specified length starting from the given position. 
2. Default Value Assignment:
   ${parameter:-word}} → If parameter is unset or null, use word.
${parameter:=word} → If parameter is unset or null, assign it the value word.
3. Parameter Replacement:
 ${parameter+word} → If parameter is set, use word; otherwise, use an empty string.
${parameter?word} → If parameter is set, use its value; otherwise, print an error message and exit.

b - what is parameter expasion in shell scripts part 2
4. Length of a Parameter:
 ${#variable} →  Returns the length of the variable.
5.Pattern Replacement:
 ${parameter/pattern/string} → Replaces the first occurrence of pattern with string.
${parameter//pattern/string} → Replaces all occurrences of pattern with string.
6. Remove Matching Prefix/Suffix:
 ${parameter#pattern} → Removes the shortest matching prefix.
${parameter##pattern} → Removes the longest matching prefix.
${parameter%pattern} → Removes the shortest matching suffix.
${parameter%%pattern} → Removes the longest matching suffix.

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