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org.sonar.l10n.shellcheck.rules.shellcheck.SC2094.html Maven / Gradle / Ivy

SC2094 Make sure not to read and write the same file in the same pipeline.
Problematic code
grep foo file.txt | sed -e 's/foo/bar/g' > file.txt

Correct code
grep foo file.txt  | sed -e 's/foo/bar/g' > tmpfile && mv tmpfile file.txt

Rationale
Each step in a pipeline runs in parallel.
In this case, grep foo file.txt will immediately try to read file.txt while sed .. > file.txt will immediately try to truncate it.
This is a race condition, and results in the file being partially or (far more likely) entirely truncated.
Exceptions
You can ignore this error if:

The file is a device or named pipe. These files don't truncate in the same way.
The command mentions the filename but doesn't read/write it, such as echo log.txt > log.txt.

Additional Resources

StackOverflow: bash redirect input from file back into same file
BashPitfalls: cat file | sed s/foo/bar/ > file