FILE IO Trouble - c

Question

I am having trouble with some file IO stuff.
I have this file:
db.dat:
Ryan
12 69.00 30.00 0.00
Bindy Lee
25 120.00 89.00 1.00
And this is my code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define RECORDS 30
#define LEN 20
main()
{
FILE *fptr;
fptr = fopen("db.dat", "r");
int i;
int counter = 2;
for (i = 0; i < counter; i++)
{
char temp1[LEN];
char temp2[LEN + 10];
fgets(temp1, LEN, fptr);
fgets(temp2, LEN, fptr);
printf("%s %s", temp1, temp2);
}
fclose(fptr);
}
I am supposed to get both lines, but I am getting this instead:
Ryan
12 69.00 30.00 0.00
Bindy Lee
Can someone please help! I don't know why I am not getting both lines, and why I am getting spaces. Very odd...Thanks!!!!

Answer 1

fgets stops after it reads LEN characters OR reaches the end of the line. I think your problem here is that you made LEN too small.
Change your printf to something more verbose like printf("temp1='%s'\ntemp2='%s'\n", temp1, temp2); and you should be able to see what was actually read into each string.

Answer 2

For the additional " ":
change:
printf("%s %s", temp1, temp2);
to
printf("%s%s", temp1, temp2);
Since the string has already contained the '\n'.
Reference:
A newline character makes fgets stop reading, but it is considered a valid
character and therefore it is included in the string copied to str.

Answer 3

You are only reading 40 bytes. If you increase the LEN you can read the remaining line,
Or instead of reading by number of bytes, you could read the entire line until there is a new line
#include <string.h>
#define RECORDS 30
#define LEN 20
main()
{
FILE *fptr;
fptr = fopen("b.db", "r");
int i;
int counter = 4;
for (i = 0; i < counter; i++)
{
char temp1[LEN];
fscanf(fptr, "%[^\n]%*c", temp1);
printf("%s\n", temp1);
}
fclose(fptr);
}
If you are interested in reading name and his corresponding record at the same time you could tweak something like,
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define RECORDS 30
#define LEN 20
main()
{
FILE *fptr;
fptr = fopen("b.db", "r");
int i;
int counter = 2;
for (i = 0; i < counter; i++)
{
char temp1[LEN];
char temp2[RECORDS];
fscanf(fptr, "%[^\n]%*c%[^\n]%*c", temp1, temp2);
printf("%s ---- %s\n", temp1, temp2);
}
fclose(fptr);
}

Answer 4

Given that you're taking structured input, you might consider using scanf instead of fgets. It isn't clear to me what you're saying with "I am supposed to get both lines".
Code that should work better for this would be something like:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define RECORDS 30
#define LEN 20
main()
{
FILE *fptr;
fptr = fopen("db.dat", "r");
int i;
int counter = 3;
for (i = 0; i < counter; i++)
{
char temp1[LEN];
char temp2[LEN + 10];
fgets(temp1, LEN, fptr);
fgets(temp2, LEN, fptr);
printf("%s%s", temp1, temp2);
}
fclose(fptr);
}
The biggest thing is you weren't reading the last line and you didn't need the space between the "%s %s" in the printf statement. "%s%s" should work fine.

Answer 5

I have a try, and debug; I find the problem just like what missingno said:
"fgets stops after it reads LEN characters OR reaches the end of the line. I think your problem here is that you made LEN too small."
the first time (count = 0), temp2 does not get the '\n';
the second time (count = 0), temp1 get the '\n';
this is why, you can have a try and debug your code.....