Software Shinobi
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Markdown
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132 lines
3.2 KiB
Markdown
Executable File
# Bash Variables
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As in any other programming language, you can use variables in Bash Scripting as well. However, there are no data types, and a variable in Bash can contain numbers as well as characters.
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To assign a value to a variable, all you need to do is use the `=` sign:
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```bash
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name="DevDojo"
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```
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>{notice} as an important note, you can not have spaces before and after the `=` sign.
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After that, to access the variable, you have to use the `$` and reference it as shown below:
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```bash
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echo $name
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```
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Wrapping the variable name between curly brackets is not required, but is considered a good practice, and I would advise you to use them whenever you can:
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```bash
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echo ${name}
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```
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The above code would output: `DevDojo` as this is the value of our `name` variable.
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Next, let's update our `devdojo.sh` script and include a variable in it.
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Again, you can open the file `devdojo.sh` with your favorite text editor, I'm using nano here to open the file:
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```bash
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nano devdojo.sh
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```
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Adding our `name` variable here in the file, with a welcome message. Our file now looks like this:
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```bash
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#!/bin/bash
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name="DevDojo"
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echo "Hi there $name"
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```
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Save it and run the file using the command below:
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```bash
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./devdojo.sh
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```
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You would see the following output on your screen:
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```bash
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Hi there DevDojo
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```
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Here is a rundown of the script written in the file:
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* `#!/bin/bash` - At first, we specified our shebang.
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* `name=DevDojo` - Then, we defined a variable called `name` and assigned a value to it.
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* `echo "Hi there $name"` - Finally, we output the content of the variable on the screen as a welcome message by using `echo`
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You can also add multiple variables in the file as shown below:
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```bash
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#!/bin/bash
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name="DevDojo"
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greeting="Hello"
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echo "$greeting $name"
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```
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Save the file and run it again:
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```bash
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./devdojo.sh
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```
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You would see the following output on your screen:
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```bash
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Hello DevDojo
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```
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Note that you don't necessarily need to add semicolon `;` at the end of each line. It works both ways, a bit like other programming language such as JavaScript!
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You can also add variables in the Command Line outside the Bash script and they can be read as parameters:
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```bash
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./devdojo.sh Bobby buddy!
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```
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This script takes in two parameters `Bobby`and `buddy!` separated by space. In the `devdojo.sh` file we have the following:
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```bash
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#!/bin/bash
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echo "Hello there" $1
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```
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`$1` is the first input (`Bobby`) in the Command Line. Similarly, there could be more inputs and they are all referenced to by the `$` sign and their respective order of input. This means that `buddy!` is referenced to using `$2`. Another useful method for reading variables is the `$@` which reads all inputs.
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So now let's change the `devdojo.sh` file to better understand:
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```bash
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#!/bin/bash
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echo "Hello there" $1
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# $1 : first parameter
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echo "Hello there" $2
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# $2 : second parameter
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echo "Hello there" $@
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# $@ : all
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```
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The output for:
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```bash
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./devdojo.sh Bobby buddy!
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```
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Would be the following:
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```bash
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Hello there Bobby
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Hello there buddy!
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Hello there Bobby buddy!
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```
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