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I have a file where i have some records like that:

test one; test one; test one; 1
test two; test two; test two; 2

I need to sort those records according to the last number, so in my previous example the second record should be at the first place, since 2>1. For this, i'm trying to add each record to an array and then apply an insertion sort algorithm. I have some problems adding each part to an array, here is my current effort:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXLEN 100

int main() {

    char one[MAXLEN] = {};
    char two[MAXLEN] = {};
    char three[MAXLEN] = {};
    int st[MAXLEN] = {};
    int i, j;

    FILE * fpointer = fopen("clients.txt", "r");


    for (i = 0; i < MAXLEN; i++) {
       fscanf(fpointer, "%s%s%s%d", &one[i], &two[i], &three[i], &st[i]);
    }


    for (j = 0; j < MAXLEN; j++) {
       printf("%s", one[i]);
    }


    fclose(fpointer);
    return 0;

}

In this example, i tried to add each field to an array, the second for loop is just a test to check whether or not data is being added to the array properly, but it's not.

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  • btw there's no attempt to sort anything here. how can we help you? Commented Aug 30, 2018 at 13:01
  • @Jean-FrançoisFabre The problem in this question is not the sorting part, i still need to get there! To get to the sorting part, i first need to store everything in some way, and i'm having problem with it Commented Aug 30, 2018 at 13:03
  • 1
    aaah but you need 2D char arrays. currently one is just a string / char array, like char one[MAXLEN][MAXSIZE] Commented Aug 30, 2018 at 13:05
  • Won't i get the "format %s expect argument of type *" if i drop the &? Commented Aug 30, 2018 at 13:06
  • drop the & once you put the 2D char array. Commented Aug 30, 2018 at 13:07

2 Answers 2

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you're currently scanning your data into 3 strings, shifting the offset by 1 each time, instead of 3 tables of strings.

You need to declare your data some other way. For example a 2D array of char

I suggest a structure instead, and an array of structures, so you have only one index (Here I'm assuming that max size for string is 100):

   typedef struct Element
   {
    char one[100];
    char two[100];
    char three[100];
    int st;
   };

  Element elements[MAXLEN];

now scan like this:

  for (i = 0; i < MAXLEN; i++) {
       Element *e = elements+i;  // pointer on ith element
       fscanf(fpointer, "%99s%99s%99s%d", e->one, e->two, e->three, &e->st);
    }

Use & on the integer, not on the strings (already pointers, they are). Also maybe it's good to check that fscanf returns 4 (error checking). The 99s ensures that you're not overflowing your strings (max len: 100 with nul terminator)

Aside: if you have strings with spaces in it, scanf isn't going to work properly, you'll have to use fgets then strtok on the semicolons to get the items

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4 Comments

Shouldn't i refer to the data structure with e.one, for example, and not with e->one? I'm getting an error with it
Solved it! the error was here in the loop: struct Element *e = elements+i;
The problem is, indeed, that i have strings of words, so i should use fgets, which is giving me some problems accessing the data structure to store them
Here is what i tried: fgets("%99s%99s%99s%d", e->one, e->two, e->three, &e->st, 255, fpointer);
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAXLEN 100
#define MAXWORDS 50
int main() {

    char one[MAXWORDS][MAXLEN] = {};
    char two[MAXWORDS][MAXLEN] = {};
    char three[MAXWORDS][MAXLEN] = {};
    int st[MAXWORDS][MAXLEN] = {};
    int i, j;

    FILE * fpointer = fopen("clients.txt", "r");


    for (i = 0; i < MAXWORDS; i++) {
       fscanf(fpointer, "%s%s%s%d", one[i], two[i], three[i], st[i]);
    }


    for (j = 0; j < MAXWORDS; j++) {
       printf("%s", one[j]);
    }


    fclose(fpointer);
    return 0;

}

check this program its working...! In this program you used the fscanf() function which can fetch data from file word by word . Here you need to take care that fscanf() wont give you the spaces as well as '\n'- line termination character .

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1 Comment

Thanks! I'm undecided on which way to use, this one or the other one with the data structure!

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