Well as the name would suggest unix system programming is the programming of the unix system.It is basically how the system has been programmed to perform.It covers the shells,various system calls and so on.I f you are interested in unix system programming than there are number of books and good tutorial the you will find usefull.. To write your own command you need to know c, basic shell scripting,system calls. For example ls command uses the open system call. BTW which OS are you using ??
Using any shell script. U need to assign required command to variable and then that variable u can use as a command with options.
