how to get file type in linux using c code example

Example 1: How to read a file in in C++

// io/read-file-sum.cpp - Read integers from file and print sum.
// Fred Swartz 2003-08-20

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

int main() {
    int sum = 0;
    int x;
    ifstream inFile;
    
    inFile.open("test.txt");
    if (!inFile) {
        cout << "Unable to open file";
        exit(1); // terminate with error
    }
    
    while (inFile >> x) {
        sum = sum + x;
    }
    
    inFile.close();
    cout << "Sum = " << sum << endl; 
    return 0;
}

Example 2: read string by string in file in linux

grep 'word' filename
grep 'word' file1 file2 file3
grep 'string1 string2'  filename
cat otherfile | grep 'something'
command | grep 'something'
command option1 | grep 'data'
grep --color 'data' fileName