something like a Split Function

[Daniel Pomrehn]

Hello

I've got a string in a char* variable. This string is entered by the user
and it can contain some \n

Now I want to split the entered text by this char into different strings.
Exists there any function to do this? The function should return e.g a
char** in which each line is.

Thanks in advance

 

[Jerry Coffin]

Hello

I've got a string in a char* variable. This string is entered by the
user and it can contain some \n

Now I want to split the entered text by this char into different
strings. Exists there any function to do this? The function should
return e.g a char** in which each line is.

You could use strtok (not really recommended) or an std::istringstream.
You might also want to look at the tokenizer in the boost library
(though it's probably overkill unless your needs are a bit more complex
than you've described above).

 

[Victor Bazarov]

I've got a string in a char* variable. This string is entered by the user
and it can contain some \n

Now I want to split the entered text by this char into different strings.
Exists there any function to do this? The function should return e.g a
char** in which each line is.

In C we used to use 'strtok' for that. I still see it in C++ code from
time to time. Try it, see if it fits.

V

 

[Phlip]

I've got a string in a char* variable. This string is entered by the user
and it can contain some \n

Please put your string in a std::string. This is not the 1970s.

Now I want to split the entered text by this char into different strings.
Exists there any function to do this? The function should return e.g a
char** in which each line is.

std::string test("This%is%a%test");
std::istringstream iss(test);
std::list<string> list;
std::string str;
while (std::getline(iss, str, '%')) {
list.push_back(str);
}

All the std:: things come from headers like <string> and <sstream>. If you
don't know these yet, learn them first before proceding, and your velocity
will be much higher.

 

[Ioannis Vranos]

Hello

I've got a string in a char* variable. This string is entered by the user
and it can contain some \n

Now I want to split the entered text by this char into different strings.
Exists there any function to do this? The function should return e.g a
char** in which each line is.

You may use std::find() to find each '\n' and split strings. Assuming a char * string:


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


std::vector<std::string> SplitString(const char * const cstring)
{
using namespace std;

const size_t SIZE= strlen(cstring);

vector<string> vec;

const char *current, *previous;

for(previous= current= cstring; current!= cstring+SIZE; )
{
current= find(previous, cstring+SIZE, '\n');

vec.push_back( string(previous, current) );

if(current!= cstring+SIZE)
previous= current+1;
}

return vec;
}



int main()
{
using namespace std;

const char *p= "Some\nTest\nString";

vector<string> vec= SplitString(p);

for(vector<string>::size_type i=0; i<vec.size(); ++i)
cout<<vec<<"\n";
}



However this is tricky and error prone. By using a std::string in the first place, it
makes things easier:


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


std::vector<std::string> SplitString(const std::string &arg)
{
using namespace std;

string &s= const_cast<string &>(arg);

vector<string> vec;

string::iterator current, previous;

for(previous= current= s.begin(); current!= s.end(); )
{
current= find(previous, s.end(), '\n');

vec.push_back( string(previous, current) );

if(current!= s.end())
previous= current+1;
}

return vec;
}



int main()
{
using namespace std;

string s= "Some\nTest\nString";

vector<string> vec= SplitString(s);

for(vector<string>::size_type i=0; i<vec.size(); ++i)
cout<<vec<<"\n";
}




The above involves vector copying, and if this produces overhead, you may do:

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


void SplitString(std::vector<std::string> &vec, const std::string &arg)
{
using namespace std;

string &s= const_cast<string &>(arg);

string::iterator current, previous;

for(previous= current= s.begin(); current!= s.end(); )
{
current= find(previous, s.end(), '\n');

vec.push_back( string(previous, current) );

if(current!= s.end())
previous= current+1;
}
}



int main()
{
using namespace std;

string s= "Some\nTest\nString";

vector<string> vec;

SplitString(vec, s);

for(vector<string>::size_type i=0; i<vec.size(); ++i)
cout<<vec<<"\n";
}