---
# System prepended metadata

title: Scripting in Bash and other sh-es 01
tags: [scripting, bash]

---

---
title: Scripting in Bash and other sh-es 01
categories: [linux, tech]
tags: [scripting, bash]
---

# Say Hello Universe in Bash

For sure, I do not want to go against the culture and start the series without a 'Hello world' kind of introduction.

In this part of the series, I purpose to understand:
- [ ] Wtf is a shell -a computer shell for that matter?
- [ ] Who's Bash?
- [ ] How to write a bash script and make it executable
- [ ] Say Hello Universe in Bash.

### Wtf is a shell

A shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation. It is named a shell because it is the outermost layer around the operating system

### Who's Bash

Command-line shells require the user to be familiar with commands and their calling syntax, and to understand concepts about the shell-specific language. Bash and other sh-es are examples of such calling syntax making them shell languages.

### How to write a bash script and make it executable.

Having understood a shell and a shell-language, it follows that a script is a series of valid syntaxes that are excuted whilst in a file. Such a file, is what is reffered to as a script. If the shell language used is Bash...it becomes a Bash Script.

There are two typical ways to write a shell script.
1. The not so proper way
2. The proper way

#### The not so proper way

As earlier mentioned, a script is a file. The not so proper way, is creating a file with the `.sh` extension.

:::success
Example: Use your fav editor. I'll be using vim.
```shell
vim script.sh
```
Now, we put some shell commands to the file. - if new to linux, you'll have to know some [basic commands](https://swcarpentry.github.io/shell-novice/reference.html)

Make it executable by adding the `x` permission to the owner/user.
```shell!
sudo chmod u+x script.sh
```
Run the script by:
```shell!
 ./script.sh
```
:::

#### The proper way - The shebang way.

Similary to the not so proper way, we start by creating a file.However, we need not include the extension `.sh`
:::success
```shell!
vim script
```
:::
Uniquely, the first line of the file is the shebang, followed by the binary to execute the script.

:::info
! A shebang is the character sequence consisting of the characters number sign and exclamation mark (#!) at the beginning of a script. It is also called sharp-exclamation, sha-bang, hashbang,pound-bang, or hash-pling.
:::

In our case, the following will be our first line. Considering the shebang and the bash binary.
```shell!
#!/bin/bash
```

:::success
Example: A proper script to list storage and check the working dir would look like:
```shell!
#!/bin/bash
ls
pwd
```
Make it executable by adding the `x` permission to the owner/user.
```shell!
sudo chmod u+x script
```
Run the script by:
```shell!
 ./script.sh
```
:::


### Say Hello Universe in Bash

After all is read and understood, it's now time to say Hello Universe in Bash. The following proper script if ran would print 'Hello Universe'

```shell!
#!/bin/bash
echo 'Hello Universe'
```

Bye. To the next ...
