How to use malloc when calling strcat()?

Question

I'm coding a small program to copy text information from a file, edit and save it to another one. When I try to execute the instruction

a=fputs( strcat( "\"", strcat(string, "\",\n")), novo_arquivo);

it gives me the segmentation fault core dumped error. Researching, I found out that I must use malloc to allocate memory, but I don't know how this code should be written.

Answer 1

A rough example of using strcat() with dynamic memory might look something like this:

#include <stdio.h>  // for printf
#include <string.h> // for strcat
#include <stdlib.h> // for calloc

int main()
{
    char* novo_arquivo = "example_string";
    // size + 3 to account for two quotes and a null terminator
    char* concat_string = calloc(strlen(novo_arquivo) + 3, sizeof(*concat_string));
    strcat(concat_string, "\"");
    strcat(concat_string, novo_arquivo);
    strcat(concat_string, "\"");
    // write concat_string to a file...
    printf("%s", concat_string);
    free(concat_string);
}

You're declaring concat_string on the heap instead of the stack, so you'll need to free it when you're finished using it, or you'll create a memory leak.