Scripting `Hello World`

Writing a Hello World program is a rite of passage in programming. Here’s how to do it in a shell script — straight from the command line on an enterprise Linux system.

Prerequisites

This guide assumes you're comfortable with vim. If not, maybe start there first.

Step-by-Step Guide

Create the script file

Starting from a shell, create and open a new file, "HelloWorld.sh", using vim:
Create HelloWorld.sh
```
vim HelloWorld.sh
```
Write the script

Inside "HelloWorld.sh", enter Insert mode and type this exactly:
Write HelloWorld.sh
```
#!/bin/bash

echo "Hello World!"
```
- The first line (#!/bin/bash) is called a shebang. It tells Linux which interpreter should run the script. In this case, it's the Bash shell.
- The blank line is optional, but it makes the script easier to read.
- The next line with the keyword echo just prints Hello World! to the screen.
Save and exit

Go back to Normal mode, save the file, and exit using :wq
Make the file executable

By default, new files aren't executable. Add that permission:
Make the file executable
```
chmod 700 HelloWorld.sh # (1)!
```
1. Using 700 gives the owner full permissions (read, write, execute) while removing all permissions for group and others. See Basic Permissions for a more thorough explanation.
Run the script

Finally, run it:
Run the script
```
./HelloWorld.sh
```

Troubleshooting

If your script didn’t run the first time, don’t worry — here are the common gotchas:

Permission denied when running `./HelloWorld.sh`

You probably forgot to make it executable. Run:
Make the file executable
```
chmod 700 HelloWorld.sh
```

`command not found` or nothing happens

Make sure you're running it with ./HelloWorld.sh and not just HelloWorld.sh. The ./ tells the shell to look in the current directory for the script.

Weird characters in the output

Make sure you typed the script exactly as shown, especially the quotes around "Hello World!".
Double-check that the first line is #!/bin/bash with no extra spaces or characters. If you leave out the !, for example, it won't work.

Using Windows line endings

If you created the script on Windows and then copied it to Linux, it may have Windows-style line endings (CRLF) instead of Unix-style (LF). This can cause issues. To fix it, run:
Convert line endings
```
dos2unix HelloWorld.sh
```

Still stuck?

Try running the script with bash -x to see what’s going on behind the scenes:
Run with bash -x
```
bash -x HelloWorld.sh
```

Scripting Hello World