less and more (paginated viewing) in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of 'less' command with a specific key press

You run less on a text file with 100 lines. After opening, you press the spacebar key once. What happens?

Linux CLI

less sample.txt

A The display moves forward by one line only.

B The display moves forward by one full screen of lines.

C The display moves backward by one full screen of lines.

D The display exits immediately.

💡 Hint

Think about how 'less' paginates content and what the spacebar does.

In 'less', pressing the spacebar moves the view forward by one full screen of text, allowing you to read the next chunk.

💻 Command Output

intermediate

Behavior of 'more' when reaching end of file

You use the command more sample.txt to view a file. When you reach the end of the file, what does 'more' do?

Linux CLI

more sample.txt

A It automatically exits and returns to the shell prompt.

B It waits for user input to scroll further even though no more lines exist.

C It loops back to the start of the file.

D It displays an error message and exits.

💡 Hint

Consider what happens when you reach the end of content in pagers.

'more' exits automatically when it reaches the end of the file, returning control to the shell.

📝 Syntax

advanced

Correct command to search forward in 'less'

Which command inside 'less' allows you to search forward for the word 'error'?

Linux CLI

less /var/log/syslog

A ?error

B #error

C :error

D /error

💡 Hint

Think about how forward and backward searches differ in 'less'.

In 'less', typing '/' followed by a pattern searches forward, while '?' searches backward.

💻 Command Output

advanced

Output of 'more' with piped input

You run the command cat file.txt | more. What is the behavior of 'more' in this case?

Linux CLI

cat file.txt | more

A 'more' ignores the input and exits immediately.

B 'more' outputs the entire content without pagination.

C 'more' paginates the output, allowing scrolling page by page.

D 'more' waits for a filename argument and shows an error.

💡 Hint

Consider how 'more' handles standard input from pipes.

'more' can paginate piped input, showing one screen at a time.

🚀 Application

expert

Combining 'less' with environment variable for default options

You want 'less' to always start with line numbers shown and ignore case in searches. Which environment variable setting achieves this?

A export LESS='-N -i'

B export LESS='-n -I'

C export LESS='-N -I'

D export LESS='-n -i'

💡 Hint

Check 'less' man page for option meanings: -N shows line numbers, -i ignores case.

The '-N' option shows line numbers, and '-i' makes searches case-insensitive. Both are uppercase/lowercase sensitive.

Practice

1. What is the main purpose of the less command in Linux?

easy

A. To delete files from the system

B. To edit text files directly in the terminal

C. To compile source code files

D. To view long text files one page at a time with easy scrolling

Solution

1. Step 1: Understand the function of less

   less is a pager program used to view text files or command output one page at a time.

2. Step 2: Compare with other options

   Options A, B, and D describe deleting, editing, and compiling, which are not functions of less.

3. Final Answer:

   To view long text files one page at a time with easy scrolling -> Option D

4. Quick Check:

   less = paginated viewing [OK]

Hint: Remember: less lets you scroll up and down easily [OK]

Common Mistakes:

• Confusing less with text editors like vi
• Thinking less edits files
• Assuming less deletes files

2. Which of the following is the correct syntax to view a file named log.txt using more?

easy

A. more > log.txt

B. more log.txt <

C. more log.txt

D. more log.txt -f

Solution

1. Step 1: Recall basic syntax of more

   The correct way to view a file is by passing the filename as an argument: more filename.

2. Step 2: Analyze options

   more log.txt < uses incomplete input redirection syntax; more > log.txt uses output redirection which is incorrect; more log.txt -f places option after filename, treating -f as a file.

3. Final Answer:

   more log.txt -> Option C

4. Quick Check:

   Use more filename to view files [OK]

Hint: Use more filename to open files quickly [OK]

Common Mistakes:

• Using output redirection instead of input
• Adding invalid options to more
• Confusing input and output redirection

3. What will be the output when you run the command ls -l /etc | less?

medium

A. Shows the detailed list of /etc directory contents one page at a time with scrolling

B. Shows an error because less cannot be used with pipes

C. Deletes the /etc directory contents

D. Lists the contents of /etc directory all at once without paging

Solution

1. Step 1: Understand the command pipeline

   ls -l /etc lists detailed contents of /etc. The pipe | sends this output to less.

2. Step 2: Effect of less on piped output

   less paginates the output, allowing scrolling through the list one page at a time.

3. Final Answer:

   Shows the detailed list of /etc directory contents one page at a time with scrolling -> Option A

4. Quick Check:

   Piping to less = paginated output [OK]

Hint: Pipe output to less to scroll long lists easily [OK]

Common Mistakes:

• Thinking less deletes files
• Assuming less shows all output at once
• Believing less cannot be used with pipes

4. You run more file.txt but the command exits immediately without showing the file content. What is the most likely reason?

medium

A. The file file.txt is empty

B. You typed more incorrectly

C. The terminal does not support paging

D. The file file.txt is a directory

Solution

1. Step 1: Consider what happens with an empty file

   If file.txt is empty, more has no content to display and exits immediately.

2. Step 2: Evaluate other options

   Typing errors would cause command not found or syntax errors; terminal support is rarely an issue; if file.txt is a directory, more would show an error.

3. Final Answer:

   The file file.txt is empty -> Option A

4. Quick Check:

   Empty file = no output from more [OK]

Hint: Empty files cause more to exit immediately [OK]

Common Mistakes:

• Assuming more always shows something
• Not checking if file is empty
• Confusing file with directory

5. You want to view a log file system.log but also want to search inside it while scrolling. Which command is best to use?

hard

A. more system.log

B. less system.log

C. cat system.log

D. head system.log

Solution

1. Step 1: Identify commands that allow searching while viewing

   less supports searching inside the file while scrolling up and down.

2. Step 2: Compare with other commands

   cat shows all content at once; more allows paging but limited searching; head shows only the first lines.

3. Final Answer:

   less system.log -> Option B

4. Quick Check:

   Use less for scrolling and searching [OK]

Hint: Use less to scroll and search inside files [OK]

Common Mistakes:

• Using cat for long files
• Choosing more which has limited search
• Using head which shows only start