how can I get string to number?

Question

I am working on the data collection, and trying to scan the title and convert that into real number,using "sscanf", but It did not give me the number as I expect, the "split function" which is wrote, is helping me to split out string vector:

#include <iostream>   // std::cout
#include <string>     // std::string, std::stod


int main() {
   string fn = "ch-683-mhz-8000.0-ksps-2016-06-20-17.24.19-utc.dat";

   vector<string> v;
   int f0, fs;
   split(fn, '-', v);

   for (int i = 0; i < v.size(); ++i) {
      cout << i << "   " << v[i] << '\n';
   }
   for(unsigned i=1; i < v.size(); i++){
       if(v[i] == "mhz"){
          std::sscanf(v[i-1], &f0);
          int ret = sscanf(v[i-1], &f0);
          cout << v[i-1] ;
       }
   }
   return 0;
}

the "vector v " will give me the result: 683 mhz 8000.0 ksps 2016 06 20 17.24.19 utc.dat

and I want to convert 683 and 8000 into real number, but I received error, even i tried to do some search from the forum:

Description Resource    Path    Location    Type
'resize' is ambiguous '
Candidates are:
void resize(unsigned long int, std::complex<float>)
'   fft.hpp /test2/src  line 186    Semantic Error
recipe for target 'src/test2.o' failed  subdir.mk   /test2/Debug/src    line 18 C/C++ Problem
'resize' is ambiguous '
Candidates are:
void resize(unsigned long int, std::complex<float>)
'   fft.hpp /test2/src  line 251    Semantic Error
cannot convert ‘std::__cxx11::basic_string<char>’ to ‘const char*’ for argument ‘1’ to ‘int sscanf(const char*, const char*, ...)’  test2.cpp   /test2/src  line 495    C/C++ Problem
cannot convert ‘std::__cxx11::basic_string<char>’ to ‘const char*’ for argument ‘1’ to ‘int sscanf(const char*, const char*, ...)’  test2.cpp   /test2/src  line 494    C/C++ Problem
Invalid arguments '
Candidates are:
int sscanf(const char *, const char *, ...)
'   test2.cpp   /test2/src  line 494    Semantic Error
Invalid arguments '
Candidates are:
int sscanf(const char *, const char *, ...)
'   test2.cpp   /test2/src  line 495    Semantic Error
make: *** [src/test2.o] Error 1 test2           C/C++ Problem

Could any one help?

Thank you so much.

You can't use `sscanf` with a `string`. You need to use `const char *` or `char *`. — Eli Sadoff, Nov 07 '16 at 01:56
Possible duplicate of [How to parse a string to an int in C++?](http://stackoverflow.com/questions/194465/how-to-parse-a-string-to-an-int-in-c) — MrEricSir, Nov 07 '16 at 02:22

score 0 · Accepted Answer · answered Nov 07 '16 at 02:23

int main()
{
    string fn = "ch-683-mhz-8000.0-ksps-2016-06-20-17.24.19-utc.dat";
    string szt1;

    for (int i = 0; i < 15; i++)
    {
        szt1 = szt1 + fn[i];
    }


    int n1;
    int n2;
    string szn1;
    string szn2;

    for (int i = 3; i < szt1.length(); i++)
    {
        if (i < 6)
        {
            szn1 = szn1 + szt1[i];
        }
    }

    for (int i = 11; i < szt1.length(); i++)
    {
            szn2 = szn2 + szt1[i];
    }

    n1 = atoi(szn1.c_str());
    n2 = atoi(szn2.c_str());

    cout << n1 << endl;
    cout << n2 << endl;

    return 0;

}

how can I get string to number?

and I want to convert 683 and 8000 into real number, but I received error, even i tried to do some search from the forum:

1 Answers1