Split a string into an array in C++

Question

Possible Duplicate:
How to split a string in C++?

I have an input file of data and each line is an entry. in each line each "field" is seperated by a white space " " so I need to split the line by space. other languages have a function called split (C#, PHP etc) but I cant find one for C++. How can I achieve this? Here is my code that gets the lines:

string line;
ifstream in(file);

while(getline(in, line)){

  // Here I would like to split each line and put them into an array

}

Solution 1

#include <sstream>  //for std::istringstream
#include <iterator> //for std::istream_iterator
#include <vector>   //for std::vector

while(std::getline(in, line))
{
    std::istringstream ss(line);
    std::istream_iterator<std::string> begin(ss), end;

    //putting all the tokens in the vector
    std::vector<std::string> arrayTokens(begin, end); 

    //arrayTokens is containing all the tokens - use it!
}

By the way, use qualified-names such as std::getline, std::ifstream like I did. It seems you've written using namespace std somewhere in your code which is considered a bad practice. So don't do that:

• Why is "using namespace std" considered bad practice?

Solution 2

vector<string> v;
boost::split(v, line, ::isspace);

http://www.boost.org/doc/libs/1_48_0/doc/html/string_algo/usage.html#id3115768

Solution 3

I have written a function for a similar requirement of mine, maybe you can use it!

std::vector<std::string> &split(const std::string &s, char delim, std::vector<std::string> &elems) 
{
    std::stringstream ss(s+' ');
    std::string item;
    while(std::getline(ss, item, delim)) 
    {
        elems.push_back(item);
    }
    return elems;
}

Solution 4

Try strtok. Look for it in the C++ reference:.

Solution 5

The code below uses strtok() to split a string into tokens and stores the tokens in a vector.

#include <iostream>
#include <algorithm>
#include <vector>
#include <string>

using namespace std;


char one_line_string[] = "hello hi how are you nice weather we are having ok then bye";
char seps[]   = " ,\t\n";
char *token;



int main()
{
   vector<string> vec_String_Lines;
   token = strtok( one_line_string, seps );

   cout << "Extracting and storing data in a vector..\n\n\n";

   while( token != NULL )
   {
      vec_String_Lines.push_back(token);
      token = strtok( NULL, seps );
   }
     cout << "Displaying end result in  vector line storage..\n\n";

    for ( int i = 0; i < vec_String_Lines.size(); ++i)
    cout << vec_String_Lines[i] << "\n";
    cout << "\n\n\n";


return 0;
}

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Comments

[jli]

strtok is a C library thing, whereas the poster is asking for how to do it correctly with C++.

[jli]

Of course you could use boost if you so desire, or another STL function to do the copying out of the stringstream.

[jli]

Can you provide a link to a discussion on why it is a bad practise to use using namespace x?

[Nawaz]

@jli: Added the link to my answer. See it.

[Cubbi]

If the input ends in whitespace, this inner while-loop generates an additional empty token in the end. The idiomatic C++ while(s >> token) does not.

[jli]

This is true. May as well edit to use that method.

[Ahoura Ghotbi]

@Nawaz thanks, Looking at my other questions, the syntax I am using and the way I am learning C++ from my instructors at uni is highly questionable :S!!!!!

[LucianMLI]

and c++ is not c?(... OMG all those years they all lied to me :D). Since when c library have stopped working in c++(or turned incorrect)?

[jli]

If you mix them, you add unnecessary dependances, among other issues.

[LucianMLI]

A link to the issues and DEPENDENCIES involved in using c in c++ please? ...I mean for all those years of wrongly compiling and using c code and libraries in c++ .

[jli]

stackoverflow.com/questions/4025869/using-mixing-c-in-c-code I guess the dependencies is not really the issue, but imo doing something like #include <iostream> #include <cstdio> gets redundant.

[jli]

Also I just realized I spelled dependencies wrong in my second comment (damn phone soft keyboards).