Write text to the single text file in multiple c files

Question

I have defined functions in multiple files. I want to write some text to the same file according to their execution same as below. I have found the way to write execution flow in different in file as below.

function1.h

#ifndef FUNCTION1_H_INCLUDED
#define FUNCTIONS_H_INCLUDED

int Sum(int a, int b);

#endif

function1.c

#include "function1.h"

int Sum(int a, int b)
{
    FILE *fp;

    fp = fopen("E:\\tmp\\test.txt", "a");
    fputs("Inside Sum function...\n", fp);
    fclose(fp);

    return a+b;
}

main.c

#include "stdio.h"
#include "function1.h"

int main() {
   int a=10, b=12;
   FILE *fp;

   fp = fopen("E:\\tmp\\test.txt", "a");
   fputs("Before Sum function...\n", fp);
   fclose(fp);

   printf("%d + %d = %d", a, b, Sum(a, b));

   fp = fopen("E:\\tmp\\test.txt", "a");
   fputs("After Sum function...\n", fp);
   fclose(fp);

}

Above solution is very difficult to handle when there are more multiple files. Is there direct way to write test.txt in multiple *.c files?

What do you mean by “very difficult to handle” ? What problem are you trying to resolve exactly ? — Paul R, Jun 29 '18 at 07:54
You could open the file in main and pass the file pointer to the function - after changing the signature - rather than hard code the file name in lots of places. I;m not clear what you would mean by multiple files — doctorlove, Jun 29 '18 at 07:56
I want to check the execution path. This is a simple example for understanding. If the execution path is working following text should be written the test.txt fiel. Before Sum function... Inside Sum function... After Sum function... — Namodaya Balaarachchi, Jun 29 '18 at 07:58
Multiple file mean main.c and function1.c. I will try this passing file pointer to the function — Namodaya Balaarachchi, Jun 29 '18 at 08:02

DDS · Answer 1 · 2018-06-29T08:00:09.253

2

Pass file pointer as argument int Sum(int a, int b, File *F) then (at the end) you can lseek to SEEK_SET to go back at beginning of file.

edited Jun 29 '18 at 08:00

answered Jun 29 '18 at 07:55

DDS

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Not in `'a'` mode surely? Why why do you want to rewind? – doctorlove Jun 29 '18 at 07:57
you don't need 'a' mode if you pass file as argument (you open it once at beginning of your program) – DDS Jun 29 '18 at 08:02
I may be muddling `'a'` and `'a+'` https://stackoverflow.com/questions/25963995/using-fseek-with-append though I;'m still not sure why you mention `SEEK_SET` – doctorlove Jun 29 '18 at 08:07
so you can open your file in `"wb"` or `"wt"` – DDS Jun 29 '18 at 08:11
Another solution is "close the file after last write" than re-open it again for last read. – DDS Jun 29 '18 at 08:22

score 2 · Accepted Answer · answered Jun 29 '18 at 07:56

You may open a file and pass its descriptor like an argument:

function1.h

#include <stdio.h>
#ifndef FUNCTION1_H_INCLUDED
#define FUNCTIONS_H_INCLUDED

int Sum(int a, int b, FILE *f);

#endif

function1.c

#include "function1.h"

int Sum(int a, int b, FILE *f)
{
    fputs("Inside Sum function...\n", f);
    return a+b;
}

main.c

#include "function1.h"

int main() {
   int a=10, b=12;
   FILE *fp;

   fp = fopen("E:\\tmp\\test.txt", "a");
   fputs("Before Sum function...\n", fp);

   printf("%d + %d = %d", a, b, Sum(a, b, fp));

   fputs("After Sum function...\n", fp);
   fclose(fp);

   return 0;
}

score 0 · Answer 3 · answered Jun 29 '18 at 09:35

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

/* Define SHOW_WHERE to turn on show_where() */
#define SHOW_WHERE

#ifdef SHOW_WHERE

#define show_where(fp) \
    fprintf(fp, "FILE=%s\tLINE=%d\tFUNC=%s\tDATE=%s\tTIME=%s\n", __FILE__, __LINE__, __FUNCTION__,  __DATE__, __TIME__); \
    fflush(fp);

#else

#define show_where(fp)

#endif

int main(int argc, char *argv[])
{
    show_where(stdout);

    return 0;
}

Write text to the single text file in multiple c files

3 Answers3