touch (create empty files) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the touch command do in Linux?

The touch command creates an empty file if it does not exist or updates the file's last modified time if it does exist.

beginner

How do you create multiple empty files at once using touch?

You list all the file names separated by spaces after touch. For example: touch file1.txt file2.txt file3.txt creates three empty files.

beginner

What happens if you use touch on a file that already exists?

The file's last access and modification timestamps are updated to the current time, but the file content stays the same.

intermediate

How can you use touch to create a file with a specific timestamp?

Use the -t option followed by the timestamp in the format [[CC]YY]MMDDhhmm[.ss]. For example: touch -t 202401011200 file.txt sets the file's timestamp to Jan 1, 2024, 12:00.

beginner

Why might you use touch in scripting or automation?

You can create placeholder files, update timestamps to trigger other processes, or ensure files exist before running commands that need them.

What does the command touch newfile.txt do if newfile.txt does not exist?

A Renames newfile.txt

B Deletes newfile.txt

C Displays the contents of newfile.txt

D Creates an empty file named newfile.txt

touch creates an empty file if it does not exist.

If file.txt exists, what does touch file.txt do?

A Updates the file's last modified time

B Deletes the file

C Changes file permissions

D Copies the file

touch updates the file's timestamps without changing its content.

How can you create three empty files named a.txt, b.txt, and c.txt in one command?

A rm a.txt b.txt c.txt

B touch a.txt b.txt c.txt

C mkdir a.txt b.txt c.txt

D cat a.txt b.txt c.txt

Listing multiple file names after touch creates all of them.

Which option with touch lets you set a custom timestamp?

A -c

B -r

C -t

D -a

The -t option sets a specific timestamp for the file.

Why might a script use touch before running another command?

A To create or update files needed by the command

B To delete files

C To change file ownership

D To compress files

touch ensures files exist or updates timestamps to trigger other actions.

Explain how the touch command works and give two common uses.

Think about creating files and changing file times.

Describe how to use touch to set a file's timestamp to a specific date and time.

Look for the option that controls time.

Practice

1. What does the touch command do in Linux?

easy

A. Copies a file to another location

B. Deletes a file permanently

C. Creates an empty file or updates the timestamp of an existing file

D. Displays the contents of a file

Solution

1. Step 1: Understand the purpose of touch

   The touch command is used to create empty files or update the modification time of existing files.

2. Step 2: Compare with other commands

   Deleting files is done with rm, copying with cp, and displaying contents with cat. None of these are touch.

3. Final Answer:

   Creates an empty file or updates the timestamp of an existing file -> Option C

4. Quick Check:

   touch = create/update file time [OK]

Hint: Remember: touch makes or updates files fast [OK]

Common Mistakes:

• Confusing touch with delete or copy commands
• Thinking touch shows file content
• Assuming touch edits file content

2. Which of the following is the correct syntax to create an empty file named notes.txt using touch?

easy

A. touch notes.txt

B. touch -c notes.txt

C. touch > notes.txt

D. touch -r notes.txt

Solution

1. Step 1: Identify the basic syntax of touch

   The basic command to create or update a file is touch filename. So touch notes.txt is correct.

2. Step 2: Understand other options

   -c prevents creating a file if it doesn't exist, > is shell redirection (not touch syntax), and -r copies timestamps from another file.

3. Final Answer:

   touch notes.txt -> Option A

4. Quick Check:

   Basic touch syntax = touch filename [OK]

Hint: Use simple: touch filename to create empty file [OK]

Common Mistakes:

• Using shell redirection instead of touch syntax
• Adding unnecessary options like -c or -r
• Confusing touch options with other commands

3. What will be the output of the following commands?

touch file1.txt file2.txt
ls -l file1.txt file2.txt

medium

A. Creates only file1.txt and ignores file2.txt

B. Shows an error because multiple files cannot be created with touch

C. Deletes file1.txt and file2.txt

D. Lists details of file1.txt and file2.txt, both created as empty files

Solution

1. Step 1: Understand touch with multiple files

   The touch command can create multiple files at once by listing them separated by spaces.

2. Step 2: Check ls -l output

   The ls -l command lists detailed info of the files, showing their size (0 bytes if empty) and timestamps.

3. Final Answer:

   Lists details of file1.txt and file2.txt, both created as empty files -> Option D

4. Quick Check:

   touch multiple files = creates all listed [OK]

Hint: touch can create many files at once by listing them [OK]

Common Mistakes:

• Thinking touch only creates one file at a time
• Expecting an error with multiple filenames
• Confusing touch with delete or move commands

4. You run touch newfile.txt but get an error: touch: cannot touch 'newfile.txt': Permission denied. What is the likely cause?

medium

A. You do not have write permission in the directory

B. The file newfile.txt already exists

C. The touch command is misspelled

D. The disk is full

Solution

1. Step 1: Analyze the error message

   The error says "Permission denied" which means the user lacks rights to create or modify files in the directory.

2. Step 2: Check other options

   If the file exists, touch updates timestamp without error. Misspelling touch causes command not found, not permission denied. Disk full causes different errors.

3. Final Answer:

   You do not have write permission in the directory -> Option A

4. Quick Check:

   Permission denied = no write access [OK]

Hint: Permission denied means no write rights in folder [OK]

Common Mistakes:

• Assuming file existence causes permission error
• Thinking touch command typo causes permission error
• Ignoring directory permissions

5. You want to create empty files named log1.txt, log2.txt, ..., log5.txt quickly using a single command. Which command achieves this?

hard

A. touch log*.txt

B. touch log{1..5}.txt

C. touch log1.txt log2.txt log3.txt log4.txt log5.txt

D. touch log[1-5].txt

Solution

1. Step 1: Understand brace expansion

   The syntax log{1..5}.txt uses brace expansion to create multiple filenames from 1 to 5.

2. Step 2: Evaluate other options

   log[1-5].txt matches single characters in brackets, not ranges. Listing all files manually works but is long. log*.txt matches existing files, not create new ones.

3. Final Answer:

   touch log{1..5}.txt -> Option B

4. Quick Check:

   Brace expansion creates multiple files fast [OK]

Hint: Use brace expansion: touch file{1..5}.ext [OK]

Common Mistakes:

• Using square brackets instead of braces for ranges
• Typing all filenames manually instead of using expansion
• Using wildcard which matches existing files only