[Solved] Why does this command fail?at 12:00 ls -l Ctrl+D — Ans: User lacks permission to use at | Linux CLI

Linux CLI - Cron and Scheduling

Why does this command fail?

at 12:00
ls -l
Ctrl+D

ANo newline after <code>ls -l</code>

BUser lacks permission to use <code>at</code>

CMissing <code>echo</code> before command

DIncorrect time format

Step-by-Step Solution

Solution:

Step 1: Understand at permissions
Users must be allowed in /etc/at.allow or not denied in /etc/at.deny to run at.
Step 2: Analyze other options
Newline after command is required but usually pressing Ctrl+D ends input correctly. Time format 12:00 is valid. echo is not needed when typing interactively.
Final Answer:
User lacks permission to use at -> Option B
Quick Check:
User permission controls at usage = B [OK]

Quick Trick: Check /etc/at.allow and /etc/at.deny files [OK]

Common Mistakes:

Master "Cron and Scheduling" in Linux CLI

9 interactive learning modes - each teaches the same concept differently

More Linux CLI Quizzes

Why does this command fail?