Write & Deploy Hello World in Bash

Problem

Create a Hello World script in Bash.

tl;dr

nano helloworld.sh

Type in your script:

#!/bin/bash
echo Hello World!

Hit Ctrl-O then Ctrl-X to save and exit the file. Then execute the script:

chmod +x helloworld.sh
./helloworld.sh

Solution

Simplest way of looking at a bash script is to consider it a macro. It's a simple list of commands that deploys command line arguments one by one. Any bash script begins with a hashbang and the path to bash:

#!/bin/bash

This tells the shell to execute any commands that follow the hashbang. You can run them on any flavour of UNIX, even OS X.

You create a Bash script by making a new file with the extension .sh in a text editor of your choice:

nano helloworld.sh

Then add hashbang header and any code you want, such as:

#!/bin/bash
echo Hello World!

Navigate to the directory the script is located in, and run it with ./filename.sh command:

./helloworld.sh

Unfortunately, this will usually give you an error, or the bash script will just fail to execute:

# ./helloworld.sh
-bash: ./helloworld.sh: Permission denied

This happens because the file you created does not have "execute" permission (i.e. the system is not allowed to execute the file). To fix it, type in:

chmod +x helloworld.sh

You can now execute your script. Congratulations, you've written your first Bash script!