Here documents (<<EOF) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this here document script?

Consider the following Bash script using a here document. What will it print when run?

Bash Scripting

cat <<EOF
Hello
World
EOF

A

Hello
World

B Hello World

C cat: EOF: No such file or directory

D EOF\nHello\nWorld

💡 Hint

The here document sends the lines between <

The cat command receives the lines 'Hello' and 'World' as input and prints them exactly, each on its own line.

💻 Command Output

intermediate

What happens if the delimiter is quoted in a here document?

What will this script output? cat <<'EOF' $HOME EOF

Bash Scripting

cat <<'EOF'
$HOME
EOF

A /home/username

B Syntax error near unexpected token `EOF'

C $HOME

D EOF

💡 Hint

Quoting the delimiter disables variable expansion inside the here document.

When the delimiter is quoted, the content is treated literally, so $HOME is not expanded.

🔧 Debug

advanced

Why does this here document script fail to run?

This script is intended to print a multi-line message, but it fails with a syntax error. Identify the cause. cat <

Bash Scripting

cat <<EOF
Hello
World

A cat command is misspelled

B Missing closing delimiter 'EOF' causes syntax error

C Here document delimiter must be quoted

D EOF must be uppercase

💡 Hint

The shell expects the ending delimiter to close the here document.

The here document must end with the exact delimiter on a line by itself. Missing it causes a syntax error.

🚀 Application

advanced

Which script correctly uses a here document to create a file with variable content?

You want to create a file named 'greeting.txt' containing the text 'Hello, Alice!'. The variable NAME='Alice' is set. Which script does this correctly?

Bash Scripting

NAME='Alice'
# Choose the correct script

A

cat <<EOF > greeting.txt
Hello, $NAME!
EOF

B

cat <<'EOF' > greeting.txt
Hello, $NAME!
EOF

C

cat <<EOF > greeting.txt
Hello, NAME!
EOF

D

cat <<EOF > greeting.txt
Hello, \$NAME!
EOF

💡 Hint

Variable expansion happens only if the delimiter is unquoted.

Option A expands $NAME to 'Alice'. Option A treats $NAME literally. Option A escapes the dollar sign, so no expansion. Option A prints 'NAME' literally.

🧠 Conceptual

expert

How does the shell treat leading tabs in here documents with <<-?

What is the effect of using <<-EOF instead of <

Bash Scripting

cat <<-EOF
	Hello
	World
EOF

A The here document is treated as a comment

B Leading spaces before content lines are stripped

C The here document delimiter must be quoted

D Leading tabs before content lines are stripped

💡 Hint

The dash after << enables a special behavior with tabs.

Using <<- allows the shell to ignore leading tab characters in the here document lines, making indentation cleaner.

Practice

1. What is the main purpose of using a here document (<

easy

A. To provide multiple lines of input or text to a command easily

B. To create a new file automatically

C. To run commands in the background

D. To define a function in the script

Solution

1. Step 1: Understand the here document concept

   A here document lets you send multiple lines of text or commands as input to a command in a script.

2. Step 2: Identify the correct purpose

   It is not for creating files, running background commands, or defining functions, but for providing multiline input.

3. Final Answer:

   To provide multiple lines of input or text to a command easily -> Option A

4. Quick Check:

   Here document = multiline input [OK]

Hint: Here documents send blocks of text to commands [OK]

Common Mistakes:

• Thinking it creates files automatically
• Confusing with background job control
• Assuming it defines functions

2. Which of the following is the correct syntax to start a here document in bash?

easy

A. command <

B. <

C. command EOF<<

D. << command EOF

Solution

1. Step 1: Recall the here document syntax

   The correct syntax places the command first, then <

2. Step 2: Match the options

   Only command <

3. Final Answer:

   command < -> Option A

4. Quick Check:

   Command before <

Hint: Command comes before <

Common Mistakes:

• Putting <
• Swapping EOF and <<
• Adding spaces incorrectly

3. What will be the output of this script?

cat <

medium

A. Hello $USER

B. Hello (your username)

C. Syntax error

D. Hello EOF

Solution

1. Step 1: Understand variable expansion in here documents

   Without quotes around EOF, variables like $USER are expanded to their values.

2. Step 2: Predict the output

   The script prints Hello followed by your actual username, not the literal $USER.

3. Final Answer:

   Hello (your username) -> Option B

4. Quick Check:

   Unquoted EOF expands variables [OK]

Hint: Unquoted EOF expands variables inside [OK]

Common Mistakes:

• Expecting $USER to print literally
• Thinking it causes syntax error
• Confusing EOF marker as output

4. Identify the error in this script snippet:

cat <<'EOF'
Hello $USER
EOF

medium

A. The EOF marker should not be quoted

B. EOF must be uppercase

C. Missing semicolon after <<'EOF'

D. Variables inside quoted EOF are not expanded, so $USER prints literally

Solution

1. Step 1: Understand quoting effect on here documents

   Quoting the EOF marker disables variable expansion inside the here document.

2. Step 2: Identify the output behavior

   Because of quotes, $USER prints literally, which may be unexpected.

3. Final Answer:

   Variables inside quoted EOF are not expanded, so $USER prints literally -> Option D

4. Quick Check:

   Quoted EOF disables variable expansion [OK]

Hint: Quoted EOF means no variable expansion [OK]

Common Mistakes:

• Thinking quotes cause syntax error
• Expecting variables to expand inside quoted EOF
• Believing EOF must be uppercase

5. You want to create a script that sends this exact text to a file, including the literal string $PATH:

Path is: $PATH

Which here document syntax should you use?

hard

A. cat <<"EOF" > file.txt
Path is: $PATH
EOF

B. cat < file.txt
Path is: $PATH
EOF

C. cat <<'EOF' > file.txt
Path is: $PATH
EOF

D. cat < file.txt
Path is: \$PATH
EOF

Solution

1. Step 1: Understand how to prevent variable expansion

   To keep $PATH literal, quote the EOF marker to disable expansion.

2. Step 2: Choose the correct syntax

   Using <<'EOF' prevents $PATH from expanding, so the exact text is written.

3. Final Answer:

   cat <<'EOF' > file.txt Path is: $PATH EOF -> Option C

4. Quick Check:

   Quote EOF to keep variables literal [OK]

Hint: Quote EOF to keep variables literal in output [OK]

Common Mistakes:

• Not quoting EOF and expecting literal $PATH
• Using escape \$PATH inside unquoted EOF
• Using double quotes which still expand variables