Get numbers only from a text file using c - c

Question

/edited/
I'm new here.
I have a text file that reads:
6
<cr>
R 0
R 1
R 4
R 36
R 0
R 4
This is what I have. I want to read each line into an array so that I can convert that array into an integer so I can print only the numbers of whichever line I want later.
#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
int main()
{
FILE *fr; /*declares file pointer*/
int i, j, num[32];
char array[32][32], input_file[32], line[32];
printf("Enter file: ");
fflush(stdin);
scanf("%s", input_file);
fr = fopen(input_file, "r");
for(i=0;i<32;i++)
for(j=0;j<32;j++){
array[i][j] = \'0';
}
for(i=0;i<32;i++){
line[i] = '\0';
}
if(fr != NULL){
while(fgets(line, sizeof(line), fr) != NULL){
strcpy(array[i],line);
num[i] = atoi(array[i]);
i++;
printf("%d\n", num[i]);
}
}fclose(fr);
else{
perror(input_file);
}
}
I'm not getting any errors but it isn't printing the right thing; this is what it prints:
-370086
-370086
-370086
-370086
-370086
-370086
-370086
-370086
Can anyone explain to me what is going wrong?

Answer 1

I think I'd handle this a bit differently. Though you haven't stated it explicitly, I'm going to assume that the first number is telling us how many more lines of letters/numbers we're going to read (not including the blank line). So, we want to read that, then read the rest of the lines, ignoring any leading non-digits, paying attention only to the numbers.
If that's correct, we can simplify the code somewhat:
int num_lines;
int i;
int *numbers;
fscanf(infile, "%d", &num_lines); // read the number of lines.
numbers = malloc(sizeof(int) * num_lines); // allocate storage for that many numbers.
// read that many numbers.
for (i=0; i<num_lines; i++)
fscanf(infile, "%*[^0123456789]%d", numbers+i);
// the "%*[^0123456789]" ignores leading non-digits. The %d converts a number.

Answer 2

There are several issues:
You're never setting input_file to anything, so you seem to be opening a random file.
You're double-using i in the nested loops.
You're not showing array at all, so it's impossible to tell how it's declared.
You are increasing the loop index before using it to print the number, so you're always "missing" and printing the number in the next (not yet written) slot.
You should use memset() to clear the arrays if you're worried. There's no need to clear arrays that are going to be overwritten, such as line which is written to by fgets().

Answer 3

Assuming array is a char array, when you do:
...
strcpy(array[i],line);
num[i] = atoi(array[i]);
...
Your actually converting the entire line and not the integer in it. You should consider using fscanf, or at least search for the integer inside the line variable and convert it.
Doing atoi(array[i]) is the same as atoi("R 32\n") for example.