Tab completion in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of pressing Tab twice after typing 'ls /et'?

You type ls /et in a Linux terminal and press the Tab key twice quickly. What will the shell display?

A It completes the command to 'ls /etc/' automatically

B It shows an error message 'command not found'

C It lists all files and directories starting with '/et', such as '/etc/'

D It clears the current command line

💡 Hint

Think about how tab completion works when multiple matches exist.

Pressing Tab twice after a partial path shows all possible completions starting with that prefix. Since '/etc/' is a directory starting with '/et', it will list it.

💻 Command Output

intermediate

What happens when you press Tab after typing a unique command prefix?

You type pyth in a Linux terminal where only the command python3 starts with 'pyth'. What happens when you press Tab once?

A It deletes the typed text

B Nothing happens, you must press Tab twice

C It shows all commands starting with 'pyth'

D The command auto-completes to 'python3'

💡 Hint

Think about how tab completion behaves with only one possible match.

If only one command matches the typed prefix, pressing Tab once completes it automatically.

📝 Syntax

advanced

Which command enables programmable tab completion for a custom script?

You want to add tab completion to your custom script named mytool. Which command correctly loads bash completion for it?

A complete -F _mytool_completion mytool

B enable_completion mytool

C tabcomplete mytool

D bash_completion mytool

💡 Hint

Look for the bash built-in command that links a function to completion.

The 'complete' command with -F option assigns a function to handle tab completion for a command.

🔧 Debug

advanced

Why does tab completion not work for your script?

You wrote a bash completion function for your script but pressing Tab does nothing. Which is the most likely cause?

A You used 'compgen' inside the function

B You forgot to run 'complete -F function_name script_name'

C You pressed Tab twice instead of once

D You named the function starting with an underscore

💡 Hint

Think about how bash knows which function to call for completion.

Without the 'complete' command linking the function to the script, bash won't use it for tab completion.

🚀 Application

expert

How to create a tab completion that suggests only files with '.txt' extension?

You want to write a bash completion function that suggests only files ending with '.txt' when pressing Tab after your command. Which snippet correctly generates this list?

A COMPREPLY=( $(compgen -f -- "$1" | grep '\.txt$') )

B COMPREPLY=( $(compgen -d -- "$1" | grep '\.txt$') )

C COMPREPLY=( $(compgen -f -- "$1") )

D COMPREPLY=( $(compgen -f -- "$1" | grep '\.jpg$') )

💡 Hint

Use 'compgen -f' to list files and filter by extension.

'compgen -f' lists files; piping to grep filters only '.txt' files for completion.