4 SC2216

Joachim Ansorg edited this page 2021-11-12 19:50:57 +01:00

Table of Contents

• Piping to rm, a command that doesn't read stdin. Wrong command or missing xargs?
• Problematic code:
• Correct code:
• Rationale:
• Exceptions:

Piping to rm, a command that doesn't read stdin. Wrong command or missing xargs?

Problematic code:

ls | echo                      # Want to print result
cat files | rm                 # Want to delete items from a file
find . -type f | cp dir        # Want to process 'find' output
rm file | true                 # Want to ignore errors

Correct code:

ls
cat files | while IFS= read -r file; do rm -- "$file"; done
find . -type f -exec cp {} dir \;
rm file || true

Rationale:

You are piping to one of several commands that don't read from stdin.

This may happen when:

• Confusing one command for another, e.g. using echo where cat was intended.
• Incorrectly refactoring, leaving a | on the previous line.
• Missing xargs, because stdin should be passed as positional parameters instead (use xargs -0 if at all possible).
• Intending to use || instead of |

Check your logic, and rewrite the command so data is passed correctly.

Exceptions:

If you've overridden a command to return output, you can either rename it to make this obvious, or ignore this message.

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