shell-scripts

Inputs

Inputs can be taken in two ways in shell scripting 1. While executing (read command) 2. Before executing (special variables)

Special Variables: 0-9, *, @, # -> Inputs

$0 -> Script Name
$1 -> First argument
$2 -> Second Argument
..... $9
$10 -> Ideally it is not a right way, But still you can access it by bounding the variable while accessing
    ${10}

$*, $@ -> All arguments.
$# -> Number of arguments.
$$ -> PID of the script 

Exit Status

? -> Exit Status.
Exit states ranges from 0-255
    0 -> Successful
    1-255 -> Failure / Partial Failure / Partial Successful
        1-125 -> Command/ script exit states
        126 -> Permission Denied
        127 -> Command not found
        128+n -> Kill Signals

        Ex: 128+n=143 => n=143-128 => n=15
    
    exit command can send custom exit status to shell
    Syntax: exit 0-255
        Ex: exit 2
            exit 0

Redirectors

![image](https://user-images.githubusercontent.com/29029753/40633488-a702b190-630d-11e8-80cb-25645bb43d5f.png)

![image](https://user-images.githubusercontent.com/29029753/40633614-64b304ec-630e-11e8-8d59-195fa9952ec6.png)

/dev/null is special property file which nullifies the output

Quotes

Conditions

Functions

Loops