Prog#235: read from file & display it until eof

/*
read from file & display it until eof
Program#235
*/
#include<stdio.h>
main(int argc,char *argv[])
{
int i,p;
char a[512];
union xyz{
struct bio{
char name [20], addr [20];
int age;
float salary;
}a;
char b[sizeof(struct bio)];
};
union xyz m;
if(argc!=2)
{
printf("file open error");
return 0;
}
p=open(argv[1], 1);
if(p==-1)
{
printf("file open error");
return 0;
}
i=read(p,m.b,sizeof(struct bio));
while(i>0)
{
printf("%s %d %f %s", m.a.name, m.a.age, m.a.salary, m.a.addr);
i=read(p,m.b,sizeof(struct bio));
}
close(p);
}