internal command in C program

[naresh6577]

Hii
I need to implement internal command :clear,dir <directory> ,environ and quit in C program using Unix..
i wrote program but i m not sure with output whether it is right or wrong
here is my code:


#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main(int argc, char *argv[])
{
int i,n;
char *s;
//extern char **environ;
extern char **environ;
if(argc==2)
{

printf("Myshell??");
scanf("%s",s);
if(strcmp(s,"clear")==0)
{
system("clear");

}
else if(strcmp(s,"quit")==0)
{
exit(0);
}
else if(strcmp(s,"environ")==0)
{

while(*environ)
printf("%s\n",*environ++);

}

}
return 0;
}





when i run my program i need to enter

a.out r
Myshell??clear
and gives output to clear sceen
but how to implement quit command(exit)and dir <directory>command??

Help me..

Thanks
Rupal