Search in file

[lexie21]

Hi, I am wondering how to search through a text file for one specific word and display what is after it. For example, search for the word Rice: and display just the price.

And i don't how to use strstr, thank you.

[MiiNiPaa]

That depends on how file is formatted.
For example if file is in format:

Beans 0.99
Carrots 1.20
Rice 3.05

Then you can use something like:

std::string name;
std::istream file("prices.dat");
bool found = false;
while( !found && file >> name) {
    if (name == "Rice") {
        double price;
        file >> price;
        std::cout << price;
        found = true; 
    }
    std::getline(file, name); //skip rest of line
}
if (!found)
    std::cout << "Rice is not found";

[lexie21]

the file is like this:
id initials products position price
10 RIC RICE 34 23

But in there's an error says "no matching fuction for call ro 'std::basic_istream<char>::basic_istream(const char [11])'

EDIT:

I know what was, a missing f in istream

[Computergeek01]

And i don't how to use strstr, thank you.

We could explain this one as well while we're at it. As the first parameter "strstr()" requires a const char pointer, conveniently enough this is what the std::string.c_str() member function returns. The second parameter is a constant pointer to the string you are looking for. So in MiiNiPaa's code the only differences would be the inclusion of the cstring header and Line 5 which would be changed to:

if(strstr(name.c_str(), "Rice") != NULL)

That wasn't so bad was it? But really there is no reason to go including another header when you could just use std::string.compare() which looks like this:

if(name.compare("Rice") == 0)

Then again, since the position of the buffer matters here I almost want to say that std::string.find() is the best candidate. Oh well, dealers choice I guess.

[lexie21]

#include<iostream>
#include<fstream>
#include<cstring>

using namespace std;

int main(){

string name;
string product;
ifstream file("productos.txt");
bool found = false;
cout<<"Product: ";
cin>>product;
while( !found && file >> name) {
    if (name == product) {
        double price;
        file >> price;
        cout << price;
        found = true;
    }
    getline(file, name); //skip rest of line
}
if (!found)
    cout << "Is not found";
}

But when i try to found a product always print is not found.

[Computergeek01]

Just throwing this out there but you do know that the comparison is case sensitive right?

[MiiNiPaa]

...And also is not compatible with yours file format.

So for the sake of possible future changes it is best to declare a structure:

struct product
{
    unsigned id;
    std::string initials;
    std::string name;
    int pos;
    int /*double?*/ price;
};
//...
std::ifstream file("products.dat");
product tmp;
/*I assume that the line "id initials products position price" is not actually in file*/
while(file >> tmp.id >> tmp.initials >> tmp.name >> tmp.pos >> tmp.price)
{
    if (tmp.name == "RICE")
        std::cout << tmp.price;
}