ps (list processes) in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this command?

You run the command ps -e | grep ssh. What does this command do?

Linux CLI

ps -e | grep ssh

A Starts the ssh service if it is not running.

B Lists only ssh processes without showing any other processes.

C Shows the ssh service status without listing processes.

D Lists all running processes and filters to show only those with 'ssh' in their name or details.

💡 Hint

Think about what 'ps -e' and 'grep ssh' do separately and then combined.

The command 'ps -e' lists all running processes. Piping it to 'grep ssh' filters the list to only show lines containing 'ssh'.

💻 Command Output

intermediate

What does this command output?

What is the output of ps -u root?

Linux CLI

ps -u root

A Lists all processes owned by the user 'root'.

B Lists all processes except those owned by 'root'.

C Shows system-wide CPU usage statistics.

D Displays the current user's processes only.

💡 Hint

The '-u' option filters processes by user.

The command lists all processes that belong to the user 'root'.

📝 Syntax

advanced

Which command correctly lists all processes with full command line?

You want to see all running processes with their full command lines. Which command is correct?

A ps auxww

B ps -e -o cmd

C ps -ef

D ps -u all

💡 Hint

Look for options that show all users and full command lines.

The 'ps auxww' command lists all processes with detailed info and full command lines. 'ps -ef' shows all processes but may truncate commands. 'ps -e -o cmd' shows commands but not full details. 'ps -u all' is invalid.

🔧 Debug

advanced

Why does this command fail?

You run ps -u without specifying a user and get an error. Why?

Linux CLI

ps -u

A Because '-u' is not a valid option for ps.

B Because '-u' requires a username argument and none was given.

C Because ps needs root privileges to run '-u'.

D Because the system has no users defined.

💡 Hint

Check the man page for the '-u' option.

The '-u' option requires a username to filter processes. Without it, ps shows an error.

🚀 Application

expert

How many processes are running under the current user?

Write a command that counts how many processes are running under your current user and outputs only the number.

A ps -u $(whoami) | wc -l

B ps -U $(whoami) | grep -c .

C ps -u $(whoami) | tail -n +2 | wc -l

D ps aux | grep $(whoami) | wc -l

💡 Hint

Remember the header line in ps output and how to exclude it.

Option C correctly lists processes for current user, skips the header line with 'tail -n +2', then counts lines. Option C counts header too. Option C uses '-U' which is similar but may differ by system. Option C counts all lines containing username, including grep itself.