History command and search in Linux CLI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to show the last 10 commands from your history.

Linux CLI

history [1]

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

A| tail -10

B-10

C-n 10

D-c 10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'history -10' which is not a valid option.

Using 'history -n 10' which reads new history lines, not last 10 commands.

The command 'history | tail -10' shows the last 10 commands from the history list.

2fill in blank

medium

Complete the code to search your command history for the word 'git'.

Linux CLI

history | grep [1]

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

A'git'

B'grep'

C"git"

Dgit

Attempts:

3 left

💡 Hint

Common Mistakes

Including quotes that may cause grep to look for literal quotes.

Searching for 'grep' instead of 'git'.

Using 'history | grep git' searches the history output for the word git.

3fill in blank

hard

Fix the error in the command to recall the last command starting with 'ssh'.

Linux CLI

![1]

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

Ass

Bssh

Csh

Dssh -p

Attempts:

3 left

💡 Hint

Common Mistakes

Typing incomplete command start like 'ss' or 'sh'.

Adding extra options after the bang which is invalid.

Using '!ssh' recalls the last command starting with 'ssh'.

4fill in blank

hard

Fill both blanks to create a command that searches history for 'docker' and shows only the last 5 results.

Linux CLI

history | grep [1] | tail [2]

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

Adocker

B10

C-5

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using '-5' with tail which is invalid.

Searching for wrong keyword in grep.

The command 'history | grep docker | tail 5' shows the last 5 history entries containing 'docker'.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps command numbers to commands containing 'python' from history output.

Linux CLI

commands = [1]: [2] for line in history_output if '[3]' in line}

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

Aline.split()[0]

B'python'

C' '.join(line.split()[1:])

Dline

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole line as key or value without splitting.

Checking for wrong keyword in the if condition.

This comprehension maps the command number (first word) to the command text (rest of the line) for lines containing 'python'.

Practice

1. What does the history command do in a Linux terminal?

easy

A. Deletes all saved commands

B. Lists all previously executed commands

C. Shows current running processes

D. Clears the terminal screen

Solution

1. Step 1: Understand the purpose of history

   The history command shows a list of commands you typed before in the terminal.

2. Step 2: Compare options with command behavior

   Only Lists all previously executed commands correctly describes this behavior; others describe different commands.

3. Final Answer:

   Lists all previously executed commands -> Option B

4. Quick Check:

   history lists past commands [OK]

Hint: Remember: history shows past commands typed [OK]

Common Mistakes:

• Confusing history with clearing screen
• Thinking history deletes commands
• Mixing history with process listing

2. Which of the following is the correct syntax to rerun the last command starting with git?

easy

A. !!git

B. !$git

C. !git

D. !^git

Solution

1. Step 1: Recall syntax for rerunning commands by prefix

   Using !string reruns the last command starting with string.

2. Step 2: Analyze options

   !git reruns last command starting with 'git'. Others are invalid or incorrect syntax.

3. Final Answer:

   !git -> Option C

4. Quick Check:

   Use !string to rerun commands [OK]

Hint: Use ! plus command start to rerun quickly [OK]

Common Mistakes:

• Using !!git which is invalid
• Confusing !$ with rerun syntax
• Trying !^git which is not correct

3. Given the following history output:

  100  ls -l
  101  git status
  102  cd projects
  103  git commit -m 'fix'

What command will run if you type !git?

medium

A. git commit -m 'fix'

B. git status

C. ls -l

D. cd projects

Solution

1. Step 1: Identify last command starting with 'git'

   From history, commands 101 and 103 start with 'git'. The last one is 103: git commit -m 'fix'.

2. Step 2: Understand !git runs last matching command

   !git reruns the most recent command starting with 'git', which is command 103.

3. Final Answer:

   git commit -m 'fix' -> Option A

4. Quick Check:

   !string runs last command starting with string [OK]

Hint: !string runs last command starting with string [OK]

Common Mistakes:

• Choosing first matching command instead of last
• Confusing command numbers with commands
• Selecting unrelated commands

4. You tried to rerun a command with !cd but got an error: bash: !cd: event not found. What is the likely cause?

medium

A. The shell does not support history

B. You typed the command incorrectly

C. You need to use !! instead

D. No previous command starts with 'cd' in history

Solution

1. Step 1: Understand error meaning

   event not found means no matching command found in history for the given prefix.

2. Step 2: Analyze cause

   If no previous command starts with 'cd', !cd fails with this error.

3. Final Answer:

   No previous command starts with 'cd' in history -> Option D

4. Quick Check:

   !string fails if no matching command [OK]

Hint: Check history for matching commands before using !string [OK]

Common Mistakes:

• Assuming syntax error instead of missing history
• Thinking shell lacks history support
• Using !! instead of !string incorrectly

5. You want to find and rerun a command that contains the word backup anywhere in it, but you don't remember the exact command start. Which is the best way to do this?

hard

A. Press Ctrl + r and type 'backup' to search interactively

B. Use !backup to rerun the command

C. Run history | grep backup and then rerun manually

D. Use !! backup to rerun last backup command

Solution

1. Step 1: Understand searching commands with unknown start

   !string only matches commands starting with string, so !backup won't find commands containing 'backup' elsewhere.

2. Step 2: Identify interactive search method

   Ctrl + r lets you search history interactively for any substring, including 'backup'.

3. Final Answer:

   Press Ctrl + r and type 'backup' to search interactively -> Option A

4. Quick Check:

   Use Ctrl + r for substring history search [OK]

Hint: Use Ctrl + r to search history by any word quickly [OK]

Common Mistakes:

• Assuming !backup matches anywhere in command
• Trying !! backup which is invalid syntax
• Relying only on grep without rerun shortcut