How to sort data in .txt file

**ipsilante** · 01-21-2021

I have a .txt file with floating point values on each line:
3.14 5.221 0.55 4.77
6.12 2.13 9.33 1.2
0.99 4.22 3.56 8.95 3.125
9.0575 4.897542 120.2324 55.555

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 256
int main(int argc, char *argv[])
{
    if(argc !=2)
    {
        printf("Invalid format.\n");
        return -1;
    }
    FILE *fin = fopen(argv[1], "rt");
    if(!fin)
    {
        printf("ERROR opening the file.\n");
        return 1;
    }
    char buf[MAX];
    int i = 0;
    float v[MAX], n;
    while(fgets(buf, MAX, fin))
    {
        buf[strlen(buf)-1] = '\0';
        char *word = strtok(buf, " ");
        while(word != NULL)
        {
            printf("Word : %s <-> %.3f\n", word, atof(word));
            //v[i] = atof(word);
            //i++;
            n = atof(word);
            word = strtok(NULL, " ");
            printf("%f\n", n);
        }
    }
    fclose(fin);
    return 0;
}

I wanna print the sets sorted by the number of digits in the decimal part. I'm thinking of using qsort maybe, but I tried placing each value in an array and only garbage values were printed. Why is that?

**laserlight** · 01-21-2021

Originally Posted by ipsilante

I wanna print the sets sorted by the number of digits in the decimal part.

You might want to elaborate on this. For example, by "set" you presumably mean a set of values on a line. Do you want to sort the values within each set? Do you want to sort the sets themselves with respect to each other?

Originally Posted by ipsilante

I'm thinking of using qsort maybe, but I tried placing each value in an array and only garbage values were printed. Why is that?

You probably can use qsort, but you're sorting an array of strings, not floats. If you try sorting floats, it simply won't work: how many "digits in the decimal part" is there?

**ipsilante** · 01-22-2021

Desired output would be:
6.12 2.13 9.33 1.2 // 7 digits in total in the decimal part
3.14 5.221 0.55 4.77 // 9 digits in total in the decimal part
0.99 4.22 3.56 8.95 3.125 // 11 digits in total in the decimal part
9.0575 4.897542 120.2324 55.555 // 17 digits in total in the decimal part

**Salem** · 01-22-2021

Well that was nothing like I expected.

Code:

#include<stdio.h>
#include<string.h>

int main ( ) {
  const char *seps = " \n";
  FILE *in = fopen("foo.txt","r");
  char buff[BUFSIZ];
  while ( fgets(buff,BUFSIZ,in) ) {
    char *p;
    for ( p = strtok(buff,seps) ; p ; p = strtok(NULL,seps) ) {
      char *q = strchr(p,'.');
      printf("Len after . in %s is %zd\n", p, strlen(q+1));
    }
  }
  fclose(in);
}

$ ./a.out 
Len after . in 3.14 is 2
Len after . in 5.221 is 3
Len after . in 0.55 is 2
Len after . in 4.77 is 2
Len after . in 6.12 is 2
Len after . in 2.13 is 2
Len after . in 9.33 is 2
Len after . in 1.2 is 1
Len after . in 0.99 is 2
Len after . in 4.22 is 2
Len after . in 3.56 is 2
Len after . in 8.95 is 2
Len after . in 3.125 is 3
Len after . in 9.0575 is 4
Len after . in 4.897542 is 6
Len after . in 120.2324 is 4
Len after . in 55.555 is 3

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