Search for a string in a binary file with C++

Question

I wrote a short program to search for a string in a binary file. The file consists of text and Base64 content. If I test it with an ASCII text file, it works. If I try it with a binary file, it does not match anything.

So can you tell me:

1. Where's my fault?
2. What is the best (computational) way to search for a string in a binary file?

UPDATE: A direct string comparison works, so the problem has to be somewhere in the regex definition.

Code

19 #include<iostream>
20 #include<fstream>
21 #include<regex>
22 #include<string>
23 
24 using namespace std;
25 
26 int main(int argc, char* argv[]) {
27     if (argc != 2){
28         cout << "Error message";
29     }
30 
31     regex type_response ("(TEST: )(.*)");
32     regex target_value ("(VALUE: )(.*)");
33     regex target_version ("(NAME: )(.*)");
34 
35     ifstream infile(argv[1], ios::binary);
36 
37     if (infile.is_open()){
38         string line;
39         while (getline(infile, line)){
40             if (regex_match(line ,target_version)){
41                 cout << line;
42             }
43         };
44     infile.close();
45 
46     return 0;
47     }
48 
49     else {
50         cout << "Could not open file.\n";
51         return 1;
52     };
53 };

Answer 1

The problem was a malformed regex, the rest of the code works.

Answer 2

An ASCII file is a binary file that stores ASCII codes and an ASCII code is a 7-bit code stored in a byte. While a binary file has no such restrictions and any of the 8 bits can be used in any byte of a binary file.

In ASCII file the highest bit of each byte is not used and it means the highest bit is treated as 0. While in binary file, it maybe 0 or 1. So there are difference. You can check the hex detail of the binary file using tools like HxD.