Question

I think that’s not a difficult question but i want to know how to do it in a C++ way. I want to search the position of a defined word or sequence.

I read this post stack similar question and the answer looks great. But i don’t know how to apply this solution with a file. This std instruction it’s easy to apply in a or a but i don’t know how to apply to a file and a sequence.

Instruction:

std::ifstream file;
std::search(std::istreambuf_iterator<char>(file.rdbuf()) // search from here
          , std::istreambuf_iterator<char>()             // ... to here
          , pSignature                                   // looking for a sequence starting with this
          , pSignature+sigSize);                         // and ending with this

Can I use a string to store the sequence to search in the file ???

Could someone post an easy example of how to apply the search instruction, i always obatin and big error when I compile it.

I don’t use windows and don’t want to use Boost library.

Thanks in advance.

Answer 1

Read the file into a string (assuming it’s not huge). You can then use string::find or std::algorithm.

using namespace std;

// read entire file into a string
ifstream file(".bashrc");
string contents((istreambuf_iterator<char>(file)), istreambuf_iterator<char>());

string needle = "export";

// search using string::find
size_t pos = contents.find(needle);
cout << "location using find: " << contents.find(needle) << endl;

// search using <algoritm>'s search
string::const_iterator it = search(contents.begin(), contents.end(), needle.begin(), needle.end());
cout << "location found using search: " << string(it, it + 10) << endl;
cout << "    at position: " << it - contents.begin() << endl;

[EDIT]
You can also search with the istreambug_iterators directly, but that leaves you with the same kind of iterator.

istreambuf_iterator<char> it2 = search(
        istreambuf_iterator<char>(file), istreambuf_iterator<char>(),
        needle.begin(), needle.end());