LFCS Essential Commands Practice Question
A junior admin runs 'ls -l' and sees permissions '-rwxrwxr-x' on a file. What is the octal representation?
⚠ Common exam trap
The trap here is that candidates often misread the last three characters 'r-x' as 'rwx' or 'r--', leading them to choose 777 or 755 instead of correctly calculating 775.
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
✓
775
The permissions '-rwxrwxr-x' break down as: owner (rwx = 4+2+1 = 7), group (rwx = 4+2+1 = 7), others (r-x = 4+0+1 = 5). This gives the octal value 775. Option C is correct because it matches this calculation exactly.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
755
Why it's wrong here
755 maps to rwxr-xr-x, giving the group only read and execute; the stem shows group write set. It is tempting as the common default permission set, and would be correct for a typical executable owned by one user.
- ✗
770
Why it's wrong here
770 maps to rwxrwx---, granting others no access, whereas the stem's final r-x grants read and execute to others. It is tempting as a restrictive shared-group setting, and would be correct for a private group-writable directory.
- ✓
775
Why this is correct
The symbolic string `-rwxrwxr-x` maps each permission triad to its octal digit: owner `rwx` equals 7, group `rwx` equals 7, and others `r-x` equals 5, giving 775. This directly satisfies the stem's requirement to convert the displayed mode into its octal equivalent.
- ✗
777
Why it's wrong here
777 grants execute to others, but the trailing r-x already includes it, so the octal is 775. The tempting 777 assumes all three triads are rwx, which suits a fully permissive file where owner, group and others each need read, write and execute.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.