如何在搜索功能中获取行信息哪条线我找到了我正在寻找的字符串？

Question

#include <string>
 #include <iostream>
#include <fstream>
 using namespace std;

 int search(string pat, string txt)

{
int M=(int)pat.length();
int N=(int)txt.length();
int occurences=0;

for (int s=0; s<=N-M; s++)
{
    int j;
    for (j=0; j<M; j++)
    {
        if (txt[s+j]!= pat[j])

            break;

    }
    if (j==M)
    {
        occurences++;
    }   
}return occurences;
}
  int main()

  {
string pat;
string txt;
int line = 1;

cout << "Pattern: ";
cin >> pat;
cout << endl;

ifstream infile("/Users/irem/Library/Developer/Xcode/DerivedData/sample2.txt");

while (getline(infile, txt))
{
    cout << "Line " << line << ": " << search(pat, txt) << " occurences" << endl;
    line++;
}
  return 0;

}

我的代码完全读取文件并在文本文件中搜索给定的字符串。但是我想要搜索函数进行字符串匹配时出现多少次出现的信息？行信息始终保持为1。