## Marking a script as executable
Sometimes, you may need to mark a script as an executable to run it. On Linux, this can be accomplished by `chmod +x [FILE]`, where `[FILE]` is the file you want to mark as executable. To unmark a file as executable, use `chmod -x`

## The Shebang
There are various shells with their own language syntax (`sh`, `bash`, `fish`, etc). Therefore, more complicated scripts will indicate a particular shell by specifying the absolute path to the interpreter as the first line, prefixed by `#!` like this:
```sh
#!/bin/sh
echo "Hello, World!"
```
`#!/bin/sh` means that this script can be executed by the binary located at `/bin/sh`, and so the reader knows this is a `sh`(ell) script.

## Variables
In bash, variable assignment is done with the `=` operator. Variables are conventionally named with `SCREAMING_SNAKE_CASE`, and can be accessed by prefixing the variable name with a dollar sign (`$`):
```bash
#!/bin/bash
# There may not be any spaces
# Assignment is done with the equal sign (=) operator:
MY_VARIABLE="

```