In UNIX/Linux file permissions, what does the second permission triad (e.g., r--) indicate for the file's group?

Introduction / Context:
UNIX file metadata shows three permission triads in ls -l output: owner, group, and others. Correctly interpreting the second triad is essential for understanding which users can read, write, or execute a file within a shared group, influencing collaboration and security settings.

Given Data / Assumptions:

• Standard permission string like -rw-r--r--.
• Order of triads: owner, group, others.
• Notation r=read, w=write, x=execute, -=no permission.

Concept / Approach:

The second triad applies to the file's owning group. If it reads r--, it grants the group read-only access (no write, no execute). The first triad affects the owner; the third affects all other users. Therefore, r-- in the middle position means “group has read permission only.”

Step-by-Step Solution:

Verification / Alternative check:

Use stat -c %A file (Linux) or ls -l to confirm triad positions; modify with chmod g+r,g-wx file to explicitly set group read-only and verify result.

Why Other Options Are Wrong:

• other has read permission only: refers to the third triad, not the second.
• owner has read permission only: refers to the first triad.
• group has write permission only: would be -w-, not r--.
• None of the above: incorrect because the group interpretation is clear.

Common Pitfalls:

• Miscounting triad positions, especially with directory entries.
• Forgetting that execute on directories controls traversal, not execution.

Final Answer:

group has read permission only.