Return values (return and echo) in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the return command do inside a bash function?

It stops the function and sends a numeric exit status (0-255) back to the caller. It does NOT send text output.

beginner

How can you send text output from a bash function?

Use echo inside the function to print text. The caller can capture this output using command substitution.

beginner

What is the difference between return and echo in bash functions?

return sends a numeric status code to indicate success or failure.
echo sends text output that can be captured or displayed.

beginner

Can return send strings or complex data in bash?

No. return only sends a number (0-255). To send strings, use echo and capture the output.

beginner

How do you capture the output of a bash function that uses echo?

Use command substitution like result=$(my_function). The variable result will hold the echoed text.

What does return 1 inside a bash function mean?

A The function prints '1' to the screen

B The function ends and sends a failure status 1

C The function sends the string '1' as output

D The function continues running

return sends a numeric exit status. return 1 means the function ended with status 1 (usually failure).

How do you get text output from a bash function?

A Use <code>echo</code> inside the function

B Use <code>print</code> command

C Use <code>return</code> with the text

D Use <code>exit</code> with text

Only echo prints text output. return only sends numeric status.

What is the valid range of numbers you can use with return in bash?

A Any integer

B Only 0 or 1

C 1 to 100

D 0 to 255

return status codes are limited to 0-255 in bash.

How do you store the text output of a bash function into a variable?

A var=$(my_function)

B var=return my_function

C var=echo my_function

D var=my_function

Use command substitution $( ) to capture output from echo inside the function.

If a bash function uses return 5, what will $? be after calling it?

A The text '5'

B 0

C 5

D 1

$? holds the exit status of the last command or function, here it will be 5.

Explain how return and echo differ in bash functions and when to use each.

Think about what you want to send back: a number or text.

Describe how to capture the output of a bash function that prints text using echo.

Remember how you capture command output in bash.

Practice

1. In bash scripting, what does the return command inside a function do?

easy

A. It stops the entire script immediately.

B. It sends a numeric status code back to the caller.

C. It prints text output to the terminal.

D. It saves the function output to a file.

Solution

1. Step 1: Understand the purpose of return in bash functions

   The return command sends a numeric exit status (0-255) back to the caller, indicating success or failure.

2. Step 2: Differentiate from echo

   Unlike echo, which prints text output, return only sends a number status, not text.

3. Final Answer:

   It sends a numeric status code back to the caller. -> Option B

4. Quick Check:

   return = numeric status [OK]

Hint: Remember: return sends number status, echo prints text [OK]

Common Mistakes:

• Thinking return prints output like echo
• Using return to output strings
• Confusing return with exit

2. Which of the following is the correct syntax to return a status code 5 from a bash function named check?

easy

A. exit 5

B. echo 5

C. return(status=5)

D. return 5

Solution

1. Step 1: Recall bash function return syntax

   To return a status code from a function, use return followed by the number, e.g., return 5.

2. Step 2: Identify incorrect options

   echo 5 prints text, return(status=5) is invalid syntax, and exit 5 exits the whole script.

3. Final Answer:

   return 5 -> Option D

4. Quick Check:

   Use return number syntax [OK]

Hint: Use 'return' followed by number to send status [OK]

Common Mistakes:

• Using echo instead of return for status
• Trying to use parentheses in return
• Using exit inside function to return status

3. What will be the output of this script?

myfunc() {
  echo "Hello"
  return 3
}
myfunc
echo $? 

medium

A. 3\nHello

B. Hello\n0

C. Hello\n3

D. 3\n3

Solution

1. Step 1: Analyze function output

   The function prints "Hello" using echo, so "Hello" appears first.

2. Step 2: Check return status and echo it

   The function returns 3, so $? after calling it is 3, which is printed next.

3. Final Answer:

   Hello\n3 -> Option C

4. Quick Check:

   echo prints text, return sets status [OK]

Hint: echo prints text first, $? shows return code after function [OK]

Common Mistakes:

• Confusing echo output with return value
• Expecting return value to print automatically
• Ignoring that $? holds last return status

4. Identify the error in this bash function:

myfunc() {
  return "Success"
}
myfunc
echo $?

medium

A. return expects a number, not a string

B. echo cannot print return values

C. Function missing parentheses

D. return must be last command in function

Solution

1. Step 1: Understand return command rules

   In bash, return must be followed by a numeric status (0-255), not a string.

2. Step 2: Identify the error in the code

   The code tries to return "Success" (a string), which causes an error.

3. Final Answer:

   return expects a number, not a string -> Option A

4. Quick Check:

   return only accepts numbers [OK]

Hint: return only accepts numbers, not text [OK]

Common Mistakes:

• Trying to return strings with return
• Confusing echo and return usage
• Assuming return prints output

5. How can you capture the text output of a bash function greet that uses echo inside, and store it in a variable msg?

hard

A. msg=$(greet)

B. msg=return greet

C. msg=`return greet`

D. msg=echo greet

Solution

1. Step 1: Understand capturing function output

   To capture text output from a function that uses echo, use command substitution: $(function_name).

2. Step 2: Identify correct syntax

   msg=$(greet) runs greet and stores its echo output in msg. Other options misuse return or echo.

3. Final Answer:

   msg=$(greet) -> Option A

4. Quick Check:

   Use $(function) to capture echo output [OK]

Hint: Use $(function) to capture echo output in variable [OK]

Common Mistakes:

• Using return instead of command substitution
• Assigning echo command directly to variable
• Using backticks incorrectly with return