Understanding chmod — mapping symbolic to octal permissions What is the octal equivalent of the command: chmod ugo+rw note (i.e., give read and write to user, group, and others on the file ‘‘note’’)?

Introduction / Context:
Unix file permissions can be expressed symbolically (u, g, o with r, w, x) or numerically (octal). Converting between the two is a fundamental skill for system administration and scripting.

Given Data / Assumptions:

• Command is chmod ugo+rw note.
• Target is a regular file named note.
• We only add read and write for user, group, and others (no execute bits).

Concept / Approach:

Octal permission digits represent rwx as bits: r=4, w=2, x=1. For each of user, group, others, sum the bits enabled. With read and write set, value is 4+2=6. Applying to all three classes yields 6 6 6, so the octal is 666.

Step-by-Step Solution:

Verification / Alternative check:

Run chmod ugo+rw note then ls -l note: you will see -rw-rw-rw-. Converting each triplet rw- to numbers confirms 6 for each class.

Why Other Options Are Wrong:

• 555: r-x for all; lacks write.
• 444: read-only; no write or execute.
• 333: -wx; no read.
• None of the above: incorrect because 666 is correct.

Common Pitfalls:

Confusing execute with write; forgetting special modes (setuid/setgid/sticky) which would add a leading octal digit; assuming directories use the same mapping (they do, but execute means “traverse”).

Final Answer:

chmod 666 note