Get output line by line from another function (another source file)? - c

Question

I have two source files: counter.c and main.c:
counter.c:
#include <stdio.h>
int counter(void) {
for(int i = 0; i < 5; i++)
printf("%d\n", i);
return 0;
}
main.c:
#include <stdio.h>
int counter(void);
int main(void) {
char *line;
counter();
return 0;
}
What I want to do is to have each line that counter() prints to be assigned to the line variable so I can do printf("%s\n", line) myself in main.c.
(edit) Unfortunately, this example doesn't translate well to my actual code so maybe I'll just put it here:
https://github.com/venetwork/venet/blob/master/venet-show.c
What I need is to access the result of running this code on a line by line basis in a different source file (GTK3 GUI). The main function for my combined code will be in this file so main() in venet-show.c should be changed to, say, show(). As of this moment I just use an IO Channel (https://developer.gnome.org/glib/stable/glib-IO-Channels.html) to "stream" the output of venet-show.c to the GUI but I want to get ride of it. Any ideas?

Answer 1

So we pass an allocated memory address and not a pointer like you had to the function. This has storage for the result. Use the return snprintf to advance the pointer so not to overwrite previous results.
#include <stdio.h>
int counter(char *answer, size_t array_len) {
for(int i = 0; i < 5; i++)
{
size_t chars_printed = snprintf(answer, array_len, "%d\n", i);
answer+=chars_printed;
array_len-=chars_printed;
}
return 0;
}
int main(void) {
char line[10000];
counter(line, sizeof(line));
printf("%s", line);
return 0;
}