Here documents (<<EOF) in Bash Scripting - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a here document that outputs "Hello World".

Bash Scripting

cat <<[1]
Hello World
EOF

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

AEOF

BEND

CSTOP

DDONE

Attempts:

3 left

💡 Hint

Common Mistakes

Using different words after << and at the end.

Forgetting to put the ending delimiter.

The delimiter after << must match the ending delimiter exactly. "EOF" is the common choice.

2fill in blank

medium

Complete the code to assign a multi-line string to a variable using a here document.

Bash Scripting

myvar=$(cat <<[1]
Line 1
Line 2
EOF
)

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

ASTOP

BEOF

CEND

DDONE

Attempts:

3 left

💡 Hint

Common Mistakes

Using different delimiters at start and end.

Not using command substitution to assign the string.

The delimiter after << must match the ending delimiter. "EOF" is commonly used.

3fill in blank

hard

Fix the error in the here document that should print a variable's value.

Bash Scripting

name="Alice"
echo <<[1]
Hello $name
EOF

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

AEOF

B"EOF"

C-EOF

D'EOF'

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around EOF which disables variable expansion.

Not using <<- when indenting the delimiter.

Using <<-EOF allows tab-indented delimiters and preserves variable expansion.

4fill in blank

hard

Fill both blanks to create a here document that does NOT expand variables.

Bash Scripting

cat <<[1]
The value is $value
[2]

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

A'EOF'

BEOF

C"EOF"

D-EOF

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted EOF which expands variables.

Mixing quoted and unquoted delimiters.

Quoting the delimiter (like 'EOF') disables variable expansion inside the here document.

5fill in blank

hard

Fill all three blanks to create a here document that strips leading tabs and expands variables.

Bash Scripting

cat <<[1]
	Line 1
	Value: $[2]
[3]

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

AEOF

Bname

C-EOF

D'EOF'

Attempts:

3 left

💡 Hint

Common Mistakes

Quoting EOF which disables variable expansion.

Using wrong variable name inside the here document.

Using <<-EOF with tabs before lines and matching EOF delimiter strips leading tabs and expands variables.

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