String suffix removal (${var%pattern}) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the syntax ${var%pattern} do in bash scripting?

It removes the shortest matching suffix pattern from the value of the variable var. This means it deletes the smallest part at the end of the string that matches pattern.

intermediate

How does ${var%%pattern} differ from ${var%pattern}?

${var%%pattern} removes the longest matching suffix pattern, while ${var%pattern} removes the shortest matching suffix pattern from the variable's value.

beginner

Example: If file="report.txt.bak", what is the result of ${file%.bak}?

The result is report.txt. It removes the shortest suffix matching .bak from the variable file.

intermediate

Why use string suffix removal instead of external commands like sed or cut?

Because string suffix removal is faster and uses built-in shell features, so it avoids starting extra programs. It is simpler and more efficient for small string changes.

beginner

What happens if the pattern does not match any suffix in ${var%pattern}?

If the pattern does not match the end of the string, the variable's value remains unchanged.

What does ${filename%.txt} do if filename="notes.txt"?

A Does nothing

B Removes the prefix '.txt' from filename

C Removes all '.txt' occurrences in filename

D Removes the suffix '.txt' from filename

It removes the shortest suffix matching '.txt' from the variable's value.

Which syntax removes the longest matching suffix pattern in bash?

A ${var%%pattern}

B ${var#pattern}

C ${var%pattern}

D ${var##pattern}

${var%%pattern} removes the longest matching suffix pattern.

If path="folder/file.tar.gz", what does ${path%.gz} return?

A folder/file.tar.gz

B folder/file.tar.g

C folder/file.tar

D folder/file.tar.gz.gz

It removes the shortest suffix '.gz' from the string.

What happens if the pattern does not match the suffix in ${var%pattern}?

A The variable is emptied

B The variable value is unchanged

C An error occurs

D The entire string is removed

If no match, the original string remains unchanged.

Why is using ${var%pattern} preferred over external tools for suffix removal?

A It is built-in and faster

B It requires installing extra software

C It is slower but more readable

D It works only on Linux

Built-in string manipulation is faster and does not require extra programs.

Explain how to remove a file extension suffix from a filename variable in bash using string suffix removal.

Think about removing the shortest suffix matching the extension.

Describe the difference between ${var%pattern} and ${var%%pattern} in bash string manipulation.

One removes the smallest matching suffix, the other the largest.