XK0-006 System Management Practice Question
A developer wants to change all occurrences of 'foo' to 'bar' in a configuration file and save the changes in-place. Which sed command should be used?
⚠ Common exam trap
XK0-006 often tests the combination of -i and g flags — candidates forget that -i alone does not make substitution global, and g alone does not modify the file.
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
✓
sed -i 's/foo/bar/g' file
The correct command is sed -i 's/foo/bar/g' file because it combines in-place editing (-i) with the global substitution flag (g), replacing every occurrence of 'foo' on each line. Without -i, changes are only printed to stdout; without g, only the first match per line is replaced.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
sed -i 's/foo/bar/' file
Why it's wrong here
Without g, it replaces only the first occurrence per line, not all.
- ✗
sed -n 's/foo/bar/p' file
Why it's wrong here
The -n and p combination suppresses default output and prints only lines where a substitution occurred, and without -i the file is never modified. It would be correct for reporting which lines contain foo, not for rewriting the configuration file in place.
- ✗
sed 's/foo/bar/g' file
Why it's wrong here
The g flag replaces every occurrence, but omitting -i sends the result to standard output and leaves the file untouched, failing the in-place requirement. It would be correct for previewing substitutions or piping the transformed text elsewhere.
- ✓
sed -i 's/foo/bar/g' file
Why this is correct
The -i flag edits the file in place, while the g suffix replaces every occurrence of foo with bar on each line rather than only the first. This satisfies the requirement to change all matches and save changes directly to the configuration file.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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