create binary file

/* makebinfile.c - Reads a file containing a sequence of text records
*                 and writes it out to a new binary files.
*                 The names of the files are passed in as command
*                 line parameters.
*/

#include <stdio.h>

#define SIZE 10
#define NAMESIZE 25

typedef struct {
char name[NAMESIZE];
int  midterm;
int final;
int homeworks;
} student;

int writeastudent(FILE *fdout, student * who){
/* Write to an open binary file fdout the content of who.
* Return the number of bytes that were written out.
*/

char * p;          /* Cursor in outputting a byte at a time */
char * limit = ((char *)who)+sizeof(student); /*Address just past who */

for (p=(char *)who;p<limit;p++){
fputc(*p, fdout);
}
return (limit - (char *)who);
}

int main (int argc, char *argv[]){
int n = 0;         /* Number of records read */
int m;             /* Number of bytes in a record */
student who;       /* Buffer for a record */

FILE *fdin;  /* File descriptor for input file */
FILE *fdout; /* File descriptor for output file */

if(argc!=3){
printf("Usage: %s infile outfile\n", argv[0]);
exit(0);
}

if((fdin=fopen(argv[1],"r"))==NULL){
perror("fopen");
exit(1);
}

if((fdout=fopen(argv[2],"w"))==NULL){
perror("fopen");
exit(1);
}

while(fscanf(fdin,"%s %d %d %d",
who.name, &who.midterm, &who.final, &who.homeworks)!=EOF){
m = writeastudent(fdout, &who);
printf("m=%d\n", m);
n++;
}

printf("n=%d\n", n);

fclose(fdin);
fclose(fdout);

}