shell_basics

# Shell Scripting Basics

## Basic CLI Commands
```
chmod (user) (group) (other) <file/directory>
```
### Linux permission scheme
```
0 = no permission
1 = x
2 = w
3 = x+w (1+2)
4 = r
5 = r+x (4+1)
6 = r+w (4+2)
7 = r+w+x (4+2+1)
```
### Simplified
```
r = 4
w = 2
x = 1
```
## Shell Basics
### Bourne Shells
1. Bourne Shell
2. Korn Shell
3. Borne Again Shell
4. POSIX Shell

### C Shells
1. C Shell
2. TENEX/TOPS C Shell
3. Z Shell

### Variables
1. Local  variables
2. Enviornment variables
3. Shell Variables