Granting execute permission (owner only): Which chmod command gives the file owner execute permission on the file 'note' (without changing other existing permissions)?
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Achmod g+x note
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Bchmod u+w note
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Cchmod u+x note
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Dchmod ugo+x note
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ENone of the above
Answer
Correct Answer: chmod u+x note
Explanation
Introduction / Context:Selective permission changes are common when turning a script into an executable. The chmod command supports symbolic modes that add (+), remove (-), or set (=) permissions for user (u), group (g), and others (o) without affecting unrelated bits.
Given Data / Assumptions:
- Target file: note.
- Goal: add execute permission for the owner only.
- Other existing permissions should remain unchanged.
Concept / Approach:
Use symbolic mode with the user class: u+x means “add execute for user.” It leaves group and others untouched. Verification is done via ls -l, which shows permission triplets as rwx.
Step-by-Step Solution:
Run chmod u+x note.Confirm with ls -l note that the owner's execute bit is set.If the file is a script, ensure it has a valid shebang (for example, #!/bin/sh).Optionally adjust group or others with g+x or o+x if needed.Use chmod u-x to remove execute permission later.Verification / Alternative check:
Execute the file (./note) if it is a script or binary. If permission denied appears, re-check owner and execute bit, and ensure the filesystem is mounted with exec allowed.
Why Other Options Are Wrong:
a: Grants execute to group, not owner.
b: Adds write, not execute, to owner.
d: Grants execute to user, group, and others, broader than requested.
e: Not applicable; option c is correct.
Common Pitfalls:
Accidentally overexposing a file with ugo+x; forgetting executable shebang for scripts; modifying permissions on a non-executable mount.
Final Answer:
chmod u+x note