CStrings, Passing to function and manipulating string?

**jamesjeffery** · 08-15-2009

Hi guys.

I've got a frustrating problem that has seriously been puzzling me for a week.

Basically, I want my function to change the text within the CString. Here is an example:

Code:

#include <stdio.h>
#include <string.h>

void change(char buffer[]) {
  strcpy(buffer, "FoobBar\n");
}

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

    char  buffer[20] = "Example";
    printf("%s\n",buffer);        // Prints example
    change(buffer);               
    printf("%s\n",buffer);        // Should print FooBar

  return 0;
}

Or

Code:

#include <stdio.h>
#include <string.h>

void change(char *buffer) {
  strcpy(buffer, "FoobBar\n");
}

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

    char  buffer[20] = "Example";
    printf("%s\n",buffer);        // Prints example
    change(buffer);               
    printf("%s\n",buffer);        // Should print FooBar

  return 0;
}

I have a feeling it's something to do with buffer[20] being stored in part of the memory I donot have access to. Any ideas on how to solve this?

Am I doing it the correct way?

**Elysia** · 08-15-2009

Both examples are correct. Is it not working in some way? Did you try it?

**jamesjeffery** · 08-15-2009

Originally Posted by Elysia

Both examples are correct. Is it not working in some way? Did you try it?

Ah, so it does. Sorry. What I did was shorten the C file, to show an example of what I was doing. The original file don't work.

Here is what I was trying to do.

Code:

#include <stdio.h>
#include <curl/curl.h>
#include <string.h>

size_t write_data(char *ptr, size_t size, size_t nmemb, char buffer[]) {
  strcpy(buffer, ptr);
  printf("%s", buffer);   // Should print out the HTML source
  return (size * nmemb);
}

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

    char  *username       = argv[1];
    char  *password       = argv[2];
    char  *url            = argv[3];
    int   startRange      = atoi(argv[4]);
    int   endRange        = atoi(argv[5]);
    char  buffer[1000];
    
    CURL *curl = curl_easy_init();
    curl_easy_setopt(curl, CURLOPT_URL, url);
    curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
    curl_easy_setopt(curl, CURLOPT_REFERER, "http://www.yahoo.com");
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)");
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION , &write_data);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, buffer);       
    curl_easy_perform(curl);
    curl_easy_cleanup(curl);

    printf("%s", buffer);   // Should hold the HTML source

  return 0;
}

**jamesjeffery** · 08-15-2009

Ah, solved it. The memory set aside for buffer was to small.

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