How to implement readlink to find the path

Question

Using the readlink function used as a solution to How do I find the location of the executable in C?, how would I get the path into a char array? Also, what do the variables buf and bufsize represent and how do I initialize them?

EDIT: I am trying to get the path of the currently running program, just like the question linked above. The answer to that question said to use readlink("proc/self/exe"). I do not know how to implement that into my program. I tried:

char buf[1024];  
string var = readlink("/proc/self/exe", buf, bufsize);  

This is obviously incorrect.

Answer 1

This Use the readlink() function properly for the correct uses of the readlink function.

If you have your path in a std::string, you could do something like this:

#include <unistd.h>
#include <limits.h>

std::string do_readlink(std::string const& path) {
    char buff[PATH_MAX];
    ssize_t len = ::readlink(path.c_str(), buff, sizeof(buff)-1);
    if (len != -1) {
      buff[len] = '\0';
      return std::string(buff);
    }
    /* handle error condition */
}

If you're only after a fixed path:

std::string get_selfpath() {
    char buff[PATH_MAX];
    ssize_t len = ::readlink("/proc/self/exe", buff, sizeof(buff)-1);
    if (len != -1) {
      buff[len] = '\0';
      return std::string(buff);
    }
    /* handle error condition */
}

To use it:

int main()
{
  std::string selfpath = get_selfpath();
  std::cout << selfpath << std::endl;
  return 0;
}