Modular programming in C (Call functions between source file)

[Heisenberg800]

Ok so I'm having some troubles with understanding modular programming in C. My program is split-up in three parts.

"main.c" - Code for the menu and function calling. (Vehicle Directory)
"file.c" Code for the file management. (Read/Write vehicles from/to file)
"header.h" - Function and struct declarations

I don't understand how to call functions in "file.c" from "main.c". I did declare the functions in "header.h". Here are the errors I get when compiling with ("gcc main.c file.c -o prog")

main.c:2:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]skriv_in();
^
main.c:2:1: error: conflicting types for 'skriv_in'
./header.h:26:6: note: previous declaration is here
void skriv_in();
^
1 warning and 1 error generated.
file.c:6:20: error: function definition is not allowed here
void skriv_in(){
^
file.c:25:24: error: function definition is not allowed here
void skriv_ut(){
^

header.h

#ifndef HEADER_H_#define HEADER_H_
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>

/* no magic numbers */
#define ANTAL_MAX_FORDON 10
#define AVSLUTA 6
static const int MAX_ALLOWED_LENGTH = 20;

/* Vehicle Data */
typedefstruct fordon {
  char namn[MAX_ALLOWED_LENGTH];
  char marke[MAX_ALLOWED_LENGTH];
  char fordonstyp[MAX_ALLOWED_LENGTH];
  char registeringsnummer[MAX_ALLOWED_LENGTH];
} fordon;
fordon f[ANTAL_MAX_FORDON];

bool add(fordon * f);
bool delete(fordon * f);
void sortera();

void skriv_in();
void skriv_ut();

#endif                          // HEADER_H_

main.c

#include "header.h"
skriv_in();

/* Function remove vehicle */
bool delete(fordon * f)
{
  fordon tmp;
  int i = 0;

  memset(&tmp.namn[0], 0, sizeof(tmp.namn));
  memset(&tmp.marke[0], 0, sizeof(tmp.marke));
  memset(&tmp.fordonstyp[0], 0, sizeof(tmp.fordonstyp));
  memset(&tmp.registeringsnummer[0], 0, sizeof(tmp.registeringsnummer));

  *f = tmp;
  returntrue;
}

/* Function add vehicle */
bool add(fordon * f)
{
  fordon tmp;
  printf("Skriv in namn: ");
  scanf("%s", tmp.namn);
  printf("Skriv in märke: ");
  scanf("%s", tmp.marke);
  printf("Skriv in fordonstyp: ");
  scanf("%s", tmp.fordonstyp);
  printf("Skriv in registeringsnummer: ");
  scanf("%s", tmp.registeringsnummer);

  *f = tmp;
  returntrue;
}

/* function sort by car brand */
void sortera()
{
  int i, j;

  fordon temp;

  for (int i = 0; i < ANTAL_MAX_FORDON; i++) {
    for (int j = i + 1; j < ANTAL_MAX_FORDON; j++) {
      if (strcmp(f[i].marke, f[j].marke) > 0 && f[j].marke[0] != '\0') {
        temp = f[i];
        f[i] = f[j];
        f[j] = temp;
      }
    }
  }
}

/* main - switch menu with safe input */
int main()
{
  int val = 1, i = 0, nummer = 0;
  char st[1024];

  while (nummer != AVSLUTA) {

    printf("\n1. Lägg till fordon");
    printf("\n2. Ta bort fordon");
    printf("\n3. Sortera efter bilmärke");
    printf("\n4. Skriv ut information om ett fordon");
    printf("\n5. Skriv ut hela fordonregistret");
    printf("\n6. Avsluta\n");
    printf(" Skriv in ett val(1-6) ");

    /* Kod för säker inmatning */
    fgets(st, sizeof(st), stdin);
    val = sscanf(st, "%d", &nummer);
    if (val != 1) {
      printf("\nFel! Välj något av alternativen 1-6.\n");
    } else {

      /* switch meny */
      switch (nummer) {
      case 1:
        i = 0;
        while (f[i].namn[0] != '\0' && i < ANTAL_MAX_FORDON) {
          i++;
        }
        printf("(%d)", i + 1);
        if (f[9].namn[0] != '\0') {
          printf("\n Registret är fullt\n");
          break;
        } else {
          add(&f[i]);
          break;
        }
        break;
      case 2:
        i = 0;
        printf("\nSkriv in platsen(1-10) på det fordon du vill ta  bort: ");
        scanf("%d", &i);
        delete(&f[i - 1]);
        break;
      case 3:
        sortera();
        break;
      case 4:
        i = 0;
        printf
            ("\nSkriv in platsen(1-10) på det fordon du vill skriva ut information om: ");
        scanf("%d", &i);
        if (i < 1 && i > ANTAL_MAX_FORDON) {
          printf("\nFel! Välj någon av platserna 1-10.\n");
        } else if (f[i - 1].namn[0] == '\0') {
          printf("\nPlatsen är tom.\n");
        } else {
          printf("%d.%s    %s    %s    %s\n", i, f[i - 1].namn, f[i - 1].marke,
                 f[i - 1].fordonstyp, f[i - 1].registeringsnummer);
        }
        break;
      case 5:
        for (i = 0; i < ANTAL_MAX_FORDON; i++) {
          printf("%d.%s    %s    %s    %s\n", i + 1, f[i].namn, f[i].marke,
                 f[i].fordonstyp, f[i].registeringsnummer);
        }
        break;
      case 6:
        skriv_ut();
        break;

      default:
        printf("\nFel! Välj något av alternativen 1-6.\n");
      }
    }
  }

  return 0;
}

file.c

#include "header.h"

int filh()
{

  void skriv_in() {
    int i = 0;
    /* Read from file */
    FILE *file1, *file2;
    file1 = fopen("labb4.txt", "r");
    if (file1 == NULL) {
      file1 = fopen("labb4.txt", "w+");
    } else {
      while (!feof(file1)) {
        for (i = 0; i < ANTAL_MAX_FORDON; i++) {
          fscanf(file1, "%s %s %s %s", f[i].namn, f[i].marke, f[i].fordonstyp,
                 f[i].registeringsnummer);
        }
        fread(&f, sizeof(f), 1, file1);
      }
    }
    fclose(file1);
  }

  /* Write to file */
  void skriv_ut() {
    FILE *file1, *file2;
    int i = 0;
    file2 = fopen("labb4.txt", "w+");
    char buf[1024];
    int needle = 0;
    memset(buf, 0, 1024);
    for (i = 0; i < 10; ++i) {
      if (f[i].namn[0] != '\0' || f[i].marke[0] != '\0'
          || f[i].fordonstyp[0] != '\0' || f[i].registeringsnummer[0] != '\0') {
        needle =
            needle + sprintf(buf + needle, "%s %s %s %s\n", f[i].namn,
                             f[i].marke, f[i].fordonstyp,
                             f[i].registeringsnummer);
      }
    }
    fwrite(buf, strlen(buf), 1, file2);
    fclose(file2);
  }
  return0;
}

[Salem]

Get rid of line 2 in main.c


Next time you post code, make sure to either
- select copy as text in your IDE
- select paste as text in your browser.

The eyesore candy store you posted is horrible.

[Heisenberg800]

Get rid of line 2 in main.c


Next time you post code, make sure to either
- select copy as text in your IDE
- select paste as text in your browser.

The eyesore candy store you posted is horrible.

Ok sorry will try to edit that out.

Line 2 in main.c is my attempt to call the function that reads in from file to the directory. The problem is that that function is in the other source file. So my compiler thinks that I want to declare the function when in fact I want to call it. I guess my question is how can I call something from file.c to main.c?

[Heisenberg800]

Get rid of line 2 in main.c

I solved my own problem. The line 2 in main.c was supposed to be placed inside "int main()".