Interview › Scripting (Bash, Groovy)
What is the difference between glob expansion and regex in the shell? [Intermediate]
Answer
Glob expansion is shell pathname matching, such as *.log matching files. Regex is pattern matching used by tools or Bash's [[ string =~ regex ]] operator. They have different syntax and different purposes.
Technical explanation
Globs are expanded by the shell before the command runs and match filenames.
Regex is usually interpreted by tools like grep, awk, sed, or by Bash inside [[ =~ ]].
Do not quote a glob when you want the shell to expand it; do quote variables that contain filenames.
Hands-on example
# Glob: files ending in .log
for file in *.log; do echo "$file"; done
# Regex: lines beginning with ERROR and a status code
grep -E '^ERROR [0-9]{3}' app.log
[[ "release-2026" =~ ^release-[0-9]{4}$ ]] && echo match
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