Read numbers separated by commas

Question

I need the sixth figure printed on a arquivo.txt. I tried to read the file and print the first six on the screen to see if it was working, then generate a file with only the value I need organized, given that I need to repeat this process for another 4,000 files, but I’m not even getting that.

The archive txt What I’m trying to read is this:

0.00053714,0.00053714,-0.00061595,0.30794,-0.00061595,0.30794,1.0001,1,0.0050735

Below is the code I made:

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

int main()
{
    FILE *arquivo;
    int i=1;
    float a[6];
    char valor[80],*token, linha;

    arquivo = fopen("arquivo.txt","r");

    if (arquivo = fopen ("arquivo.txt", "r") == NULL)
    {
        printf ("Error opening file\n");

        getch();
    }

    fgets(valor, 80, arquivo);
    printf("STRING ----> %s\n", linha);
    token = strtok(valor,",");
    while(token!=NULL)
    {
        token=strtok(NULL,",");

        if(token!=NULL)
        {
            a[i]=atoi(token);
            i++;
        }
    }

    for(i=1;i<7;i++)
        printf("a[%d] = %f\n", i, a[i]);

    return 0;
}

Answer 1

Create a program that asks you what is the position of the value (element) you need, and search for this value according to the chosen position, it also separates the values by comma "," as your need expressed in the question.

Let’s take the example, follow the example below:

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

int main(void)
{
    FILE* file = fopen("arquivo.txt", "r");

    char line[256];
    char * valor;
    char * valor_escolhido;

    int cont_elemento = 1, posicao_elemento;

    printf("Informe a possicao ° do valor, (exemplo 1, 2 ou 6): ");
    scanf("%d", &posicao_elemento);

    if (file == NULL)
        return EXIT_FAILURE;

    /*Faz a leitura do arquivo linha por linha.*/
    while (fgets(line, sizeof(line), file))
    {
        /*Pega o primeiro elemento separado por uma virgula.*/
        valor = strtok(line,",");

        /*Obtem os outros elementos até o fim da linha.*/
        while (valor != NULL)
        {
            printf("%s\n",valor);
            valor = strtok(NULL, ",");

            cont_elemento++;

            if (cont_elemento == posicao_elemento)
                valor_escolhido = valor;
        }
    }

    printf("\n\nValor escolhido: %s\n\n", valor_escolhido);

    fclose(file);

    return EXIT_SUCCESS;
}

I used the function strtok that is part of header string.h, it can be used when we need to break a string into C using a delimiter, so that it will return its parts according to the value specified in delimiter which in this case is the comma ,. View the function signature strtok:

char * strtok ( char * str, const char * delimiters );

Explanation of the program.

I assumed that the structure of your file is in the following format according to the contents of the same that was informed in the question, follows the structure of the file that will be the input data:

0.00053714,0.00053714,-0.00061595,0.30794,-0.00061595,0.30794,1.0001,1,0.0050735

The program will ask the value position (element):

Enter the possible ° of the value, (example 1, 2 or 6):

Value I informed you:

6

I chose the 6° (sixth) element, and it will return me the value 0.30794.

Exit from the program.

Based on the input data that was reported to the program in the above example, the program will generate the following output:

0.00053714
0.00053714
-0.00061595
0.30794
-0.00061595
0.30794
1.0001 1
0.0050735

Chosen value: 0.30794

Completion.

To get the chosen value you have to count the number of occurrences issued by the function strtok using the variable cont_elemento, and do the validation to compare to the chosen position in a if, see: if (cont_elemento == posicao_elemento), then just assign the string with the separate value by the function to the string valor_escolhido, so I got the chosen value.

Sources:
Split string in C Every white space.
Split string into tokens.
How to use the Strtok() function to break a C string using delimiters.

Answer 2

awk is almost C

awk -F, '{print $6}' arquivo.txt

Simplified explanation: Internally awk divides each row into fields (in this case the field separator is , due to -F,), each field is assigned a number $1, $2, ...$n just tell us what we want to print.