Thread: Programm C fix

I have measured data divided into 100 steps. I want to read this data in C and save the temperature as a latex file. It should be output with a nice temperature curve. On the Y axis the temperature should appear and on the X axis the 100 steps. But this does not work for me. Can someone fix me the code? The data file looks like this:
x y temperature
0.292886,-0.015196,21.379749
.
.
.
X and y are not important. Only temperature is important

Code:

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

int main() {
    FILE *input_file, *tex_file;

    input_file = fopen("result.csv", "r");
    if (!input_file) {
        printf("fail to open result.csv\n");
        exit(1);
    }

    tex_file = fopen("path.tex", "w");
    if (!tex_file) {
        printf("fail to open path.tex\n");
        exit(1);
    }

    // write tex head
    const char *tex_head =
        "\\documentclass{report} \\usepackage{tikz} \\begin{document} "
        "\\begin{tikzpicture}[x=0.1cm,y=0.1cm] \\draw\n";
    fputs(tex_head, tex_file);

    char line[1024];
    double x, y, z;
    while (fgets(line, sizeof(line), input_file)) {
        char *save = line;

        char *_z = strtok_r(NULL, ",", &save);
        z = atof(_z);
        fprintf(tex_file, "(%f,%f,%f)--",z);
    }
    fprintf(tex_file, "(%f,%f,%f);\n", z);

    // write tex tail
    const char *tex_tail = "\\end{tikzpicture} \\end{document}";
    fputs(tex_tail, tex_file);

    fclose(input_file);
    fclose(tex_file);
}

Other errors when compiled in gcc v. 10.2.1:

Code:

foo.c:31:20: warning: initialization of ‘char *’ from ‘int’ makes pointer from integer without a cast [-Wint-conversion]
foo.c:33:33: warning: format ‘%f’ expects a matching ‘double’ argument [-Wformat=]
   33 |         fprintf(tex_file, "(%f,%f,%f)--",z);
      |                                ~^
      |                                 |
      |                                 double
foo.c:33:36: warning: format ‘%f’ expects a matching ‘double’ argument [-Wformat=]
   33 |         fprintf(tex_file, "(%f,%f,%f)--",z);
      |                                   ~^
      |                                    |
      |                                    double
foo.c:35:29: warning: format ‘%f’ expects a matching ‘double’ argument [-Wformat=]
   35 |     fprintf(tex_file, "(%f,%f,%f);\n", z);
      |                            ~^
      |                             |
      |                             double
foo.c:35:32: warning: format ‘%f’ expects a matching ‘double’ argument [-Wformat=]
   35 |     fprintf(tex_file, "(%f,%f,%f);\n", z);
      |                               ~^
      |                                |
      |                                double
foo.c:27:15: warning: unused variable ‘y’ [-Wunused-variable]
   27 |     double x, y, z;
      |               ^
foo.c:27:12: warning: unused variable ‘x’ [-Wunused-variable]
   27 |     double x, y, z;
      |            ^

strtok_r() may not be available on all systems.

Originally Posted by rstanley

You would first need to provide a sample data file so the code could be tested.

Here is the .csv file. I get no compiling error.

> On the Y axis the temperature should appear and on the X axis the 100 steps.
So you should only be outputting pairs of numbers to begin with.

Using strtok is messy, because you also need to have a loop to step over the first pair of values you're not interested in.

sscanf is much simpler.

Code:

    char line[1024];
    double x = 0, temperature;
    while (fgets(line, sizeof(line), input_file)) {
        if ( sscanf(line,"%*f,%*f,%f", &temperature) == 1 ) {
            fprintf(tex_file, "(%f,%f)--",x,temperature);
            x++
        }
    }