LFCS Essential Commands Practice Question
An administrator needs to replace all occurrences of the string 'foo' with 'bar' in all files under /etc/config, but only in files ending with .conf. The replacement must be done in-place, and backup copies should be created with a .bak extension. Which command accomplishes this?
⚠ Common exam trap
Test-takers frequently confuse the syntax `-i .bak` (with a space, which is incorrect) with `-i.bak` (no space, which is correct), or they forget that `-i` without a suffix does not create backups, leading them to choose options that either fail or omit the required backup step.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
find /etc/config -name '*.conf' -exec sed -i.bak 's/foo/bar/g' {} +
It uses `sed -i.bak` which creates a backup file with the .bak extension before performing the in-place substitution, and the `find -exec ... +` variant efficiently processes multiple files at once. The `-i` option with an argument (no space) specifies the backup suffix directly, satisfying the requirement for backup copies.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
find /etc/config -name '*.conf' -exec sed -i .bak 's/foo/bar/g' {} +
Why it's wrong here
Incorrect syntax; -i requires extension immediately after.
- ✗
find /etc/config -name '*.conf' -exec sed 's/foo/bar/g' {} \;
Why it's wrong here
Prints to stdout, no in-place modification.
- ✓
find /etc/config -name '*.conf' -exec sed -i.bak 's/foo/bar/g' {} +
Why this is correct
-i.bak creates backup with .bak extension.
- ✗
find /etc/config -name '*.conf' -exec sed -i 's/foo/bar/g' {} +
Why it's wrong here
Does not create backup files.
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