Executing another program in C

#include
#include
#include
void main(void)
{
int MAXLINE = 1024;
char buf[MAXLINE];
pid_t pid;
int status;
printf("%%");
while(fgets(buf,MAXLINE,stdin)!=NULL)
{
buf[strlen(buf)-1]=0;
if(pid=fork()<0)
err_sys("FORK ERROR");
else if(pid==0)
{
execlp(buf,buf,(char *)0);
err_ret("Couldn't Execute : %s",buf);
exit(127);
}
if((pid=waitpid(pid,&status,0))<0)
err_sys("Wait Pid Error");
printf("%%");
}
exit(0);
}