Shebang line (#!/bin/bash) in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this script with a shebang?

Consider this bash script saved as test.sh and made executable:

#!/bin/bash
echo "Hello from script!"

What will be the output when you run ./test.sh in a terminal?

Bash Scripting

#!/bin/bash
echo "Hello from script!"

A Hello from script!

B bash: ./test.sh: command not found

C Syntax error near unexpected token `echo'

D No output, script runs silently

💡 Hint

The shebang line tells the system which program to use to run the script.

The shebang #!/bin/bash tells the system to use bash to run the script. The echo command prints the text to the terminal.

💻 Command Output

intermediate

What happens if the shebang line is missing?

Consider this script saved as myscript.sh and made executable with chmod +x myscript.sh:

echo "Running script"

What will be the output when you run ./myscript.sh in a terminal?

Bash Scripting

echo "Running script"

A Nothing happens, script does not run

B bash: ./myscript.sh: cannot execute binary file: Exec format error

C Syntax error: missing shebang

D Running script

💡 Hint

Without a shebang, the system may not know how to run the script.

Without a shebang, the system uses the current shell to run the script, so the echo command runs and prints the text.

📝 Syntax

advanced

Identify the correct shebang line for bash scripts

Which of the following lines is the correct shebang to start a bash script?

A #!/bin/bash -c

B #!/bin/bash

C #!/bin/sh -x

D #!/usr/bin/python

💡 Hint

The shebang must point to the bash executable without extra arguments.

The correct shebang for bash is exactly #!/bin/bash. Options with python or extra flags are incorrect for a simple bash script.

🔧 Debug

advanced

Why does this script fail to run with ./script.sh?

You have this script:

#!/bin/bash
echo "Start"
exit 0

But when you run ./script.sh, you get bash: ./script.sh: Permission denied. What is the cause?

Bash Scripting

#!/bin/bash
echo "Start"
exit 0

A The echo command is misspelled

B The shebang line is incorrect

C The script file does not have execute permission

D The script has a syntax error

💡 Hint

Check the file permissions with ls -l.

Permission denied means the file is not executable. Use chmod +x script.sh to fix.

🚀 Application

expert

How to write a portable shebang line for bash scripts?

You want your bash script to run on different systems where bash might be in different locations. Which shebang line is best to ensure portability?

A #!/usr/bin/env bash

B #!/bin/bash

C #!/bin/sh

D #!/usr/local/bin/bash

💡 Hint

Use env to find bash in the user's PATH.

Using #!/usr/bin/env bash runs bash from the PATH, making the script portable across systems.