SHELL SPECIAL CHARACTERS

> hello
>
> anyone can help in clarifying in simple and detailed manner the meaning
> shell special characters for example
>
> # ps auwwx | grep "[i]nit" and ps auwwx | grep '[i]nit'
>
> dmesg | grep "[ ]ata\ |^ata"
>
>
> Regards
>
> Joe Joseph