fg and bg commands in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to resume a stopped job in the foreground.

Linux CLI

fg [1]

Drag options to blanks, or click blank then click option'

A1

Bresume

Cjob1

D%1

Attempts:

3 left

💡 Hint

Common Mistakes

Using the job number without the percent sign.

Typing the word 'resume' instead of the job reference.

The fg command uses % followed by the job number to bring a job to the foreground.

2fill in blank

medium

Complete the command to send a job to the background.

Linux CLI

bg [1]

Drag options to blanks, or click blank then click option'

A%2

Bjob1

C2

Dbackground

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the percent sign before the job number.

Using descriptive words instead of job references.

The bg command uses % followed by the job number to resume a job in the background.

3fill in blank

hard

Fix the error in the command to bring job 3 to the foreground.

Linux CLI

fg [1]

Drag options to blanks, or click blank then click option'

Ajob3

B3

C%3

Dforeground

Attempts:

3 left

💡 Hint

Common Mistakes

Using only the job number without the percent sign.

Typing descriptive words instead of job references.

The fg command requires the job to be referenced with a percent sign and the job number.

4fill in blank

hard

Fill both blanks to send job 4 to the background and then bring it to the foreground.

Linux CLI

bg [1]
fg [2]

Drag options to blanks, or click blank then click option'

A%4

B4

C%5

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using job numbers without the percent sign.

Using different job numbers for bg and fg.

Both bg and fg commands require the job to be referenced with % and the job number.

5fill in blank

hard

Fill all three blanks to list jobs, send job 2 to background, and then bring it to foreground.

Linux CLI

jobs
bg [1]
fg [2]
jobs [3]

Drag options to blanks, or click blank then click option'

A%2

B2

C-l

D-p

Attempts:

3 left

💡 Hint

Common Mistakes

Using job number without percent sign for bg and fg.

Using incorrect option for jobs command.

Use %2 to specify job 2 for bg and fg. The jobs command with -l shows process IDs.

Practice

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

easy

A. Brings a background job to the foreground for interaction

B. Stops a running job immediately

C. Lists all running jobs

D. Terminates a background job

Solution

1. Step 1: Understand the purpose of fg

   The fg command is used to bring a job running in the background to the foreground so you can interact with it directly.

2. Step 2: Compare with other commands

   jobs lists jobs, bg resumes jobs in background, and stopping or terminating jobs use other commands.

3. Final Answer:

   Brings a background job to the foreground for interaction -> Option A

4. Quick Check:

   fg = bring job to foreground [OK]

Hint: Remember: fg = foreground, bg = background [OK]

Common Mistakes:

• Confusing fg with bg
• Thinking fg lists jobs
• Assuming fg stops jobs

2. Which of the following is the correct syntax to resume a stopped job in the background?

easy

A. fg %1

B. bg %1

C. jobs %1

D. stop %1

Solution

1. Step 1: Identify the command to resume a stopped job in background

   The bg command resumes a stopped job in the background, allowing the terminal to be free.

2. Step 2: Understand job specification

   Using %1 specifies job number 1. So bg %1 resumes job 1 in background.

3. Final Answer:

   bg %1 -> Option B

4. Quick Check:

   bg %jobnumber resumes job in background [OK]

Hint: Use bg with %jobnumber to resume in background [OK]

Common Mistakes:

• Using fg instead of bg to resume in background
• Trying to use jobs command to resume
• Using stop which is invalid

3. Given the following commands run in a terminal:

sleep 100 &
jobs
fg %1

What will happen after running fg %1?

medium

A. The sleep command will continue running in the background

B. An error will occur because %1 is invalid

C. The sleep command will be terminated

D. The sleep command will be brought to the foreground and block the terminal

Solution

1. Step 1: Analyze the commands

   sleep 100 & runs sleep in background. jobs lists it as job 1. fg %1 brings job 1 to foreground.

2. Step 2: Understand effect of fg

   Bringing sleep to foreground means it blocks terminal until it finishes or is stopped.

3. Final Answer:

   The sleep command will be brought to the foreground and block the terminal -> Option D

4. Quick Check:

   fg %1 = foreground job blocks terminal [OK]

Hint: fg brings job to foreground and blocks terminal [OK]

Common Mistakes:

• Thinking fg keeps job in background
• Assuming fg terminates job
• Believing %1 is invalid without jobs output

4. You ran a command in the background with sleep 200 & but accidentally typed fg 1 instead of fg %1. What will happen?

medium

A. The job will be brought to foreground successfully

B. The job will continue running in background silently

C. An error message will appear: 'fg: 1: no such job'

D. The shell will terminate

Solution

1. Step 1: Understand job specification syntax

   The fg command requires job IDs to be prefixed with %, e.g., fg %1.

2. Step 2: Analyze incorrect command

   Typing fg 1 without % causes shell to look for a job named '1' which does not exist, causing an error.

3. Final Answer:

   An error message will appear: 'fg: 1: no such job' -> Option C

4. Quick Check:

   Job IDs need % prefix for fg/bg [OK]

Hint: Always prefix job number with % in fg/bg commands [OK]

Common Mistakes:

• Omitting % before job number
• Assuming fg accepts plain numbers
• Ignoring error messages

5. You have two stopped jobs listed by jobs as:

[1]+  Stopped                 nano file1.txt
[2]-  Stopped                 vim file2.txt

How do you resume vim file2.txt in the background and then bring nano file1.txt to the foreground?

hard

A. bg %2 followed by fg %1

B. fg %2 followed by bg %1

C. bg %1 followed by fg %2

D. fg %1 followed by fg %2

Solution

1. Step 1: Resume vim in background

   Use bg %2 to resume job 2 (vim) in background so it runs without blocking terminal.

2. Step 2: Bring nano to foreground

   Use fg %1 to bring job 1 (nano) to foreground for interaction.

3. Final Answer:

   bg %2 followed by fg %1 -> Option A

4. Quick Check:

   bg %job runs in background, fg %job runs in foreground [OK]

Hint: Use bg for background, fg for foreground with correct job IDs [OK]

Common Mistakes:

• Mixing up job numbers
• Using fg for both jobs
• Not using % before job number