Load numbers from text file in C

Question

Hi everyone, I'm wanting to load a known number of numbers into an array in C from a text file (.txt). The format would be:

"0,1,2,5,4"

I'm kinda new to C, can anyone recommend a way to load in the text file?

Cheers

Answer 1

how about strtok?

Answer 2

Sounds like a job for fopen.

Answer 3

or fopen and strtok :)

Answer 4

You can:

1) Read one number at a time and convert to int using atoi()

2) You can read the whole array at once and using strtok to divide the number and after that convert with atoi()

Here there is an example of strtok:

  int main(int argc, char *argv[])
{
        int x = 1;
        char str[]="this:is:a:test:of:string:tokenizing";
        char *str1;

        /* print what we have so far */
        printf("String: %s\n", str);

        /* extract first string from string sequence */
        str1 = strtok(str, ":");

        /* print first string after tokenized */
        printf("%i: %s\n", x, str1);

        /* loop until finishied */
        while (1)
        {
                /* extract string from string sequence */
                str1 = strtok(NULL, ":");

                /* check if there is nothing else to extract */
                if (str1 == NULL)
                {
                        printf("Tokenizing complete\n");
                        exit(0);
                }

                /* print string after tokenized */
                printf("%i: %s\n", x, str1);
                x++;
        }

        return 0;

Answer 5

Hy try this.

#include <stdio.h>
#define MAX_NUMBERS   1000    /* Max numbers in file */
const char DATA_FILE[] = "numbers.dat";  /* File with numbers */

int data[MAX_NUMBERS];  /* Array of numbers  */

int main()
{
    FILE *in_file;  /* Input file */
    int  middle;    /* Middle of our search range */
    int low, high;  /* Upper/lower bound */
    int search;    /* number to search for */
    char line[80];  /* Input line */

    in_file = fopen(DATA_FILE, "r");
    if (in_file == NULL) {
  fprintf(stderr,"Error:Unable to open %s\n", DATA_FILE);
  exit (8);
    }

    /*
     * Read in data 
     */

    max_count = 0;
    while (1) {
  if (fgets(line, sizeof(line),  in_file) == NULL)
      break;

  /* convert number */
  sscanf(line, "%d", &data[max_count]);
  ++max_count;
    return data;
   }
   return (0);
}

Answer 6

It can be done easily with fscanf:

#include <stdio.h>
int main()
{
    FILE* f = fopen("test.txt", "r");
    int number = 0;
    int sum = 0; /* the sum of numbers in the file */

    while( fscanf(f, "%d,", &number) > 0 ) // parse %d followed by ','
    {
     sum += number; // instead of sum you could put your numbers in an array
    }

    fclose(f);
}

---

@pmg: Sure, why not. I just though if it is a hw, then it is a bad thing to give a complete solution :)

#include <stdio.h>
int main()
{
    FILE* f = fopen("test.txt", "r");
    int n = 0, i = 0;
    int numbers[5]; // assuming there are only 5 numbers in the file

    while( fscanf(f, "%d,", &n) > 0 ) // parse %d followed by ','
    {
     numbers[i++] = n;
    }

    fclose(f);
}