Octal basics — owner has read and write only If a file has read and write permissions for the owner (no execute), what is the single octal digit representing the owner’s permissions?

Introduction / Context:
Unix permissions are often compressed into octal digits: one for owner, one for group, one for others. This question checks whether you can map “read+write only” into its correct octal digit.

Given Data / Assumptions:

• Owner has read (r) and write (w).
• Owner does not have execute (x).
• We only need the single digit for the owner, not the full three-digit mode.

Concept / Approach:

The mapping is r=4, w=2, x=1. Add the bits that are present to get the octal digit. For rw-, compute 4 + 2.

Step-by-Step Solution:

Verification / Alternative check:

Create a file and run chmod u=rw,go=---. ls -l will show -rw-------; converting rw- to octal gives 6 for the owner.

Why Other Options Are Wrong:

• 1: represents execute only.
• 5: equals r+x (4+1), not rw.
• 3: equals w+x (2+1), not rw.
• None of the above: incorrect because 6 is correct.

Common Pitfalls:

Confusing the bit weights; thinking the digits are decimal instead of octal; forgetting that absence of execute for regular files is common by default.

Final Answer:

6