how to remove substring from string c++

Question

I have a string s="home/dir/folder/name"

I want to split s in s1="home/dir/folder" and s2="name";

I did:

char *token = strtok( const_cast<char*>(s.c_str() ), "/" );
std::string name;
std::vector<int> values;
while ( token != NULL )
{
    name=token;

    token = strtok( NULL, "/" );
}

now s1=name. What about s2?

Answer 1

I'd recommend against using strtok. Take a look at Boost Tokenizer instead (here are some examples).

Alternatively, to simply find the position of the last '/', you could use std::string::rfind:

#include <string>
#include <iostream>

int main() {
  std::string s = "home/dir/folder/name";
  std::string::size_type p = s.rfind('/');
  if (p == std::string::npos) {
    std::cerr << "s contains no forward slashes" << std::endl;
  } else {
    std::string s1(s, 0, p);
    std::string s2(s, p + 1);
    std::cout << "s1=[" << s1 << "]" << std::endl;
    std::cout << "s2=[" << s2 << "]" << std::endl;
  }
  return 0;
}

Answer 2

If your goal is only to get the position of the last \ or / in your string, you might use string::find_last_of which does exactly that.

From there, you can use string::substr or the constructor for std::string that takes iterators to get the sub-part you want.

Just make sure the original string contains at least a \ or /, or that you handle the case properly.

Here is a function that does what you need and returns a pair containing the two parts of the path. If the specified path does not contain any \ or / characters, the whole path is returned as a second member of the pair and the first member is empty. If the path ends with a / or \, the second member is empty.

using std::pair;
using std::string;

pair<string, string> extract_filename(const std::string& path)
{
  const string::size_type p = path.find_last_of("/\\");

  // No separator: a string like "filename" is assumed.
  if (p == string::npos)
    return pair<string, string>("", path);

  // Ends with a separator: a string like "my/path/" is assumed.
  if (p == path.size())
    return pair<string, string(path.substr(0, p), "");

  // A string like "my/path/filename" is assumed.
  return pair<string, string>(path.substr(0, p), path.substr(p + 1));
}

Of course you might as well modify this function to throw an error instead of gracefully exiting when the path does not have the expected format.