jobs command in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the jobs command do in Linux?

The jobs command shows the list of background and suspended jobs in the current shell session.

beginner

How do you identify a job's status using the jobs command?

The jobs command shows each job with a status like Running, Stopped, or Done next to its job number.

beginner

What symbol is used to refer to a job in commands like fg or bg?

A job is referred to by a percent sign % followed by the job number, for example, %1 for job number 1.

intermediate

How can you list all jobs including those from other sessions?

The jobs command only shows jobs from the current shell session. To see jobs from other sessions, you need to use other tools like ps.

intermediate

What does the jobs -l option do?

The jobs -l option shows the job list with the process IDs (PIDs) of each job, giving more detailed information.

What does the jobs command display?

A List of users logged into the system

B List of all running processes on the system

C List of background and stopped jobs in the current shell

D List of files in the current directory

The jobs command shows only the background and stopped jobs in the current shell session.

How do you refer to job number 2 when using fg or bg commands?

A %2

B $2

C 2

D #2

Jobs are referenced with a percent sign and the job number, like %2.

What does the status 'Stopped' mean in the jobs output?

A The job is running in the background

B The job is not found

C The job has finished successfully

D The job is paused and waiting

'Stopped' means the job is paused (usually by pressing Ctrl+Z) and waiting to be resumed.

Which option with jobs shows process IDs?

A -l

B -p

C -r

D -s

The -l option shows the job list with process IDs.

Can jobs show jobs from other terminal sessions?

A Yes, always

B No, only current shell session

C Only if run as root

D Only if jobs are running in background

The jobs command only shows jobs from the current shell session.

Explain how to use the jobs command to check background tasks and how to bring a job back to the foreground.

Think about how you see jobs and how you can control them.

Describe the difference between the jobs command and the ps command in Linux.

Consider what each command is designed to show.

Practice

1. What does the jobs command do in a Linux shell?

easy

A. Lists background and stopped tasks in the current shell

B. Shows all running processes on the system

C. Terminates all background jobs

D. Starts a new background job

Solution

1. Step 1: Understand the purpose of jobs

   The jobs command shows tasks started in the current shell that are either stopped or running in the background.

2. Step 2: Compare with other options

   Options A, B, and C describe different commands or actions unrelated to jobs.

3. Final Answer:

   Lists background and stopped tasks in the current shell -> Option A

4. Quick Check:

   jobs lists current shell jobs [OK]

Hint: Remember: jobs shows your shell's paused or background tasks [OK]

Common Mistakes:

• Confusing jobs with ps command
• Thinking jobs starts or kills tasks
• Assuming jobs shows system-wide processes

2. Which of the following is the correct syntax to list all jobs with their process IDs using the jobs command?

easy

A. jobs -a

B. jobs --list-pid

C. jobs -p

D. jobs -l

Solution

1. Step 1: Recall jobs options

   The -l option with jobs lists jobs with their process IDs.

2. Step 2: Verify other options

   -p lists only PIDs without job info, --list-pid is invalid, and -a shows all jobs including those not started by the shell.

3. Final Answer:

   jobs -l -> Option D

4. Quick Check:

   jobs -l shows jobs with PIDs [OK]

Hint: Use -l to see job numbers plus process IDs [OK]

Common Mistakes:

• Using invalid options like --list-pid
• Confusing -p with -l
• Assuming -a shows PIDs

3. Given the following shell session:

$ sleep 100 &
[1] 12345
$ sleep 200 &
[2] 12346
$ jobs
[1]+  Running                 sleep 100 &
[2]-  Running                 sleep 200 &

What will be the output of jobs -l?

medium

A. [1]+ 12345 Stopped sleep 100 &
[2]- 12346 Stopped sleep 200 &

B. [1]+ Running sleep 100 &
[2]- Running sleep 200 &

C. [1]+ 12345 Running sleep 100 &
[2]- 12346 Running sleep 200 &

D. No jobs to display

Solution

1. Step 1: Understand jobs output

   The jobs command shows job number, status, and command. The -l option adds the process ID after the job number.

2. Step 2: Match output format

   Since both jobs are running with PIDs 12345 and 12346, jobs -l will show job number, PID, status, and command.

3. Final Answer:

   [1]+ 12345 Running sleep 100 & [2]- 12346 Running sleep 200 & -> Option C

4. Quick Check:

   jobs -l adds PIDs to normal jobs output [OK]

Hint: jobs -l shows PIDs next to job numbers [OK]

Common Mistakes:

• Ignoring PIDs in output
• Confusing Running with Stopped status
• Expecting no jobs listed

4. You ran sleep 300 & and then jobs shows the job as stopped. Which command will resume the job in the background?

medium

A. kill %1

B. bg %1

C. fg %1

D. stop %1

Solution

1. Step 1: Understand job states and commands

   A stopped job is paused. The bg command resumes it in the background, while fg resumes it in the foreground.

2. Step 2: Choose correct command for background resume

   Since the question asks to resume in background, bg %1 is correct. kill terminates, and stop is invalid here.

3. Final Answer:

   bg %1 -> Option B

4. Quick Check:

   Resume stopped job in background = bg %job_number [OK]

Hint: Use bg %job_number to resume stopped jobs in background [OK]

Common Mistakes:

• Using fg instead of bg for background resume
• Trying to kill instead of resume
• Using invalid stop command

5. You have multiple background jobs running. You want to bring job number 3 to the foreground and then stop it temporarily. Which sequence of commands should you use?

hard

A. fg %3, then press Ctrl+Z

B. bg %3, then press Ctrl+C

C. kill %3, then fg %3

D. jobs %3, then stop %3

Solution

1. Step 1: Bring job 3 to foreground

   Use fg %3 to bring job number 3 to the foreground so you can interact with it.

2. Step 2: Stop the job temporarily

   Pressing Ctrl+Z sends a stop signal, pausing the job and returning control to the shell.

3. Final Answer:

   fg %3, then press Ctrl+Z -> Option A

4. Quick Check:

   Foreground job then Ctrl+Z to stop it [OK]

Hint: Use fg %job then Ctrl+Z to pause foreground job [OK]

Common Mistakes:

• Using bg instead of fg to bring job forward
• Trying to kill instead of stop
• Using invalid stop command