c++ - Saving a paragraph in map and printing - Not Working

Question

This is related to the answer to my previous question by Mats Petersson.

According to his method, I can successfully save the line in the header and print it out later whenever I want. However, I now want to save the whole header to print it later. I am using append() to fulfill that purpose. But it's not working.

Here is the code that is outside the two functions:

static map<string, string> headermap;
static char headerline[1024];

Here is the code for the reading function:

string paragraph;

for (int i=0; i<8; ++i) {//8 lines of the header
    fgets(buffer,1024,fp);
    if(buffer[0] == '#'){
        paragraph = paragraph.append(buffer);
    }
}

headermap[filename] = paragraph;

Here is the code for the writing function:

const char *headerline = headermap[filename].c_str();
fprintf(fp, headerline);

Previously I was using headerline[i] = buffer[i]; instead of paragraph.append(buffer); in the reading function. And headermap[filename] = headerline; instead of headermap[filename] = paragraph;.

When I print, nothing is printed to the output file. As i said before, previously when I tried to print just one line, it works fine.