Interview › Scripting (Bash, Groovy)
What is the difference between ${var%pattern} and ${var#pattern}? [Intermediate]
Answer
${var%pattern} removes the shortest matching suffix, while ${var#pattern} removes the shortest matching prefix. Double versions, %% and ##, remove the longest matching suffix or prefix.
Technical explanation
These patterns are shell globs, not regular expressions.
They are useful for extracting filenames, extensions, directory parts, tags, and prefixes without calling external tools.
Using built-in parameter expansion is faster and avoids quoting issues around command substitution.
Hands-on example
path="/var/log/app/server.log.gz"
echo "dir=${path%/*}" # /var/log/app
echo "file=${path##*/}" # server.log.gz
echo "no_gz=${path%.gz}" # /var/log/app/server.log
echo "ext=${path##*.}" # gz
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