7 SC2045

François-Xavier Noé edited this page 2021-10-25 15:55:44 +02:00

Table of Contents

• Iterating over ls output is fragile. Use globs.
• Problematic code:
• Correct code:
• Rationale:
• Related resources:

Iterating over ls output is fragile. Use globs.

Problematic code:

for f in $(ls *.wav)
do
  echo "$f"
done

Correct code:

for f in *.wav
do
  [[ -e "$f" ]] || break  # handle the case of no *.wav files
  echo "$f"
done

Also note that in Bash, shopt -s nullglob will allow the loop to run 0 times instead of 1 if there are no matches. There are also several other conditions to be aware of.

Rationale:

When looping over a set of files, it's always better to use globs when possible. Using command expansion causes word splitting and glob expansion, which will cause problems for certain filenames (typically first seen when trying to process a file with spaces in the name).

The following files can or will break the first loop:

touch 'filename with spaces.wav'
touch 'filename with * globs.wav'
touch 'More_Globs[2003].wav'
touch 'files_with_fønny_chæracters_in_certain_locales.wav'

Related resources:

• Bash Pitfalls: for i in $(ls *.mp3)

• How to loop over directories in Linux?

ShellCheck

• Installation

  • CentOS6
  • More Installation Guides

• Usage

  • Directive
  • Ignore

• Integrating and extending

  • Misc. contributions
  • Azure Pipelines
  • Buildkite
  • CircleCI
  • DevGuide
  • Integration
  • JUnit
  • Phabricator
  • TravisCI
  • GitLab CI
  • Drone
  • GitHub Actions

• Severity

• Template

Each individual ShellCheck warning has its own wiki page like SC1000. Use GitHub Wiki's "Pages" feature above to find a specific one, or see Checks.