Running scripts in Bash Scripting - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the command to make a script executable in Bash?

Use chmod +x scriptname.sh to give execute permission to the script.

beginner

How do you run a Bash script located in the current directory?

Run it by typing ./scriptname.sh in the terminal.

beginner

Why do you need ./ before the script name when running it?

Because the current directory is not in the PATH by default, ./ tells the shell to run the script from here.

beginner

What does the first line #!/bin/bash in a script do?

It tells the system to use the Bash shell to run the script. This line is called the shebang.

intermediate

Can you run a script without making it executable? How?

Yes, by running bash scriptname.sh or sh scriptname.sh you can run the script without changing permissions.

What command makes a Bash script executable?

A chmod +x script.sh

B run script.sh

C execute script.sh

D bash +x script.sh

The chmod +x command adds execute permission to the script.

How do you run a script named myscript.sh in the current folder?

A bash ./myscript.sh

B myscript.sh

C ./myscript.sh

D run myscript.sh

You run it with ./myscript.sh because the current directory is not in PATH.

What is the purpose of the shebang line #!/bin/bash?

A To comment the first line

B To name the script

C To make the script executable

D To tell the system which shell to use to run the script

The shebang tells the system to use Bash to run the script.

If you do not want to change permissions, how can you run a script?

A bash script.sh

B ./script.sh

C chmod script.sh

D execute script.sh

Running bash script.sh runs the script without needing execute permission.

Why do you need to type ./ before the script name?

A Because it is part of the script name

B Because current directory is not in PATH by default

C Because it makes the script executable

D Because it is a command to run scripts

The shell does not look in the current folder unless you specify ./.

Explain step-by-step how to prepare and run a Bash script from creating it to executing it.

Think about file creation, permissions, and running commands.

Describe why the current directory is not searched by default when running commands and how to run scripts in the current directory.

Consider how the shell finds commands.

Practice

1. What is the correct way to run a bash script named myscript.sh after making it executable?

easy

A. Use ./myscript.sh to run the script.

B. Use run myscript.sh to run the script.

C. Use execute myscript.sh to run the script.

D. Use start myscript.sh to run the script.

Solution

1. Step 1: Understand script execution permission

   Before running a script with ./myscript.sh, it must have execute permission set using chmod +x myscript.sh.

2. Step 2: Run the script using relative path

   Using ./myscript.sh runs the script in the current directory. Other commands like run, execute, or start are not valid bash commands.

3. Final Answer:

   Use ./myscript.sh to run the script. -> Option A

4. Quick Check:

   Executable script run with ./script.sh = A [OK]

Hint: Make script executable, then run with ./script.sh [OK]

Common Mistakes:

• Trying to run script without execute permission
• Using invalid commands like run or start
• Not specifying path to script

2. Which of the following is the correct syntax to run a bash script named backup.sh without changing its permissions?

easy

A. ./backup.sh

B. sh run backup.sh

C. bash backup.sh

D. execute backup.sh

Solution

1. Step 1: Understand running scripts without execute permission

   If the script is not executable, you can run it by explicitly calling the shell interpreter like bash backup.sh.

2. Step 2: Identify correct syntax

   bash backup.sh runs the script using bash without needing execute permission. Other options either require execute permission or are invalid commands.

3. Final Answer:

   bash backup.sh -> Option C

4. Quick Check:

   Run script with interpreter command = B [OK]

Hint: Use bash script.sh to run without execute permission [OK]

Common Mistakes:

• Trying to run with ./ without execute permission
• Using invalid commands like execute
• Adding extra words like 'run' before script name

3. Given the script hello.sh with content:

#!/bin/bash
echo "Hello, $1!"

What is the output of ./hello.sh World?

medium

A. Hello, $1!

B. Hello, World!

C. Hello, !

D. Syntax error

Solution

1. Step 1: Understand script parameter usage

   The script uses $1 which is the first argument passed to the script. Here, World is passed as the first argument.

2. Step 2: Predict output after substitution

   The echo command prints "Hello, World!" by replacing $1 with the argument.

3. Final Answer:

   Hello, World! -> Option B

4. Quick Check:

   Argument $1 replaced by 'World' = A [OK]

Hint: Arguments like $1 print passed values in scripts [OK]

Common Mistakes:

• Printing literal $1 instead of argument
• Missing argument causing empty output
• Assuming syntax error due to shebang

4. You try to run a script with ./myscript.sh but get Permission denied. What is the most likely fix?

medium

A. Add execute permission with chmod +x myscript.sh.

B. Run the script with ./myscript.sh again.

C. Rename the script to myscript.sh.sh.

D. Delete the script and create a new one.

Solution

1. Step 1: Identify cause of 'Permission denied'

   This error usually means the script file does not have execute permission.

2. Step 2: Fix permission issue

   Use chmod +x myscript.sh to add execute permission, allowing the script to run.

3. Final Answer:

   Add execute permission with chmod +x myscript.sh. -> Option A

4. Quick Check:

   Permission denied fixed by chmod +x = D [OK]

Hint: Use chmod +x to fix permission denied errors [OK]

Common Mistakes:

• Trying to run script again without changing permissions
• Renaming script does not fix permissions
• Deleting script is unnecessary

5. You want to run a script deploy.sh located in /home/user/scripts from anywhere in the terminal without typing the full path. What is the best way to do this?

hard

A. Run the script with bash /home/user/scripts/deploy.sh every time.

B. Copy deploy.sh to /tmp directory.

C. Rename the script to deploy without extension.

D. Add /home/user/scripts to the PATH environment variable.

Solution

1. Step 1: Understand PATH environment variable

   PATH lists directories where the shell looks for commands. Adding a directory lets you run scripts inside it by name.

2. Step 2: Add script directory to PATH

   By adding /home/user/scripts to PATH, you can run deploy.sh from anywhere simply by typing deploy.sh.

3. Final Answer:

   Add /home/user/scripts to the PATH environment variable. -> Option D

4. Quick Check:

   PATH addition enables running scripts anywhere = C [OK]

Hint: Add script folder to PATH to run scripts anywhere [OK]

Common Mistakes:

• Copying script to /tmp is temporary and not recommended
• Running with full path every time is inconvenient
• Renaming script does not affect running from anywhere