Output not as expected in fwrite - c

Question

I am learning fread and fwrite of c and made a basic code to write a structure using fwrite in a file . Output was there on the
#include<stdio.h>
int main()
{
FILE *f;
int i,q=0;
typedef struct {
int a;
char ab[10];
}b;
b var[2];
f=fopen("new.c","w");
printf("Enter values in structure\n");
for(i=0 ; i<2 ; i++)
{
scanf("%d",&var[i].a);
scanf("%s",var[i].ab);
}
fwrite(var,sizeof(var),1,f);
fclose(f);
return 0;
}
The output was not smooth as it contained weird characters inside the file. I opened the file in binary mode too but in vain. Is this some kind of buffer problem?

Answer 1

The "weird" characters inside your file are probably the bytes of the binary integers you're writing out. fwrite is writing the bits of var directly to the file, not converting that into a human readable format. If you want that, use fprintf instead.
Here's an example directly from your code above:
$ ./example
Enter values in structure
5 hello
8 world
$ hexdump -vC new.c
00000000 05 00 00 00 68 65 6c 6c 6f 00 00 00 00 00 00 00 |....hello.......|
00000010 08 00 00 00 77 6f 72 6c 64 00 00 00 00 00 00 00 |....world.......|
00000020
Notice that the first four bytes at offset 0x00 and 0x10 are the numbers entered (little-endian and 32-bit because of my machine), followed by the strings entered, plus a bit of structure padding. All broken down:
File Offset Data (ASCII) Relationship to source
0 05 var[0].a 7:0
1 00 var[0].a 15:8
2 00 var[0].a 23:16
3 00 var[0].a 31:24
4 68 (h) var[0].ab[0]
5 65 (e) var[0].ab[1]
6 6c (l) var[0].ab[2]
7 6c (l) var[0].ab[3]
8 6f (o) var[0].ab[4]
9 00 (NUL) var[0].ab[5]
10 00 (NUL) var[0].ab[6]
11 00 (NUL) var[0].ab[7]
12 00 (NUL) var[0].ab[8]
13 00 (NUL) var[0].ab[9]
14 00 structure padding
15 00 structure padding
16 08 var[1].a 7:0
17 00 var[1].a 15:8
18 00 var[1].a 23:16
19 00 var[1].a 31:24
20 77 (w) var[1].ab[0]
21 6f (o) var[1].ab[1]
22 72 (r) var[1].ab[2]
23 6c (l) var[1].ab[3]
24 64 (d) var[1].ab[4]
25 00 (NUL) var[1].ab[5]
26 00 (NUL) var[1].ab[6]
27 00 (NUL) var[1].ab[7]
28 00 (NUL) var[1].ab[8]
29 00 (NUL) var[1].ab[9]
30 00 structure padding
31 00 structure padding