Reading piped input with C++

c++ pipe stdin cin
user181351 picture user181351 · Mar 27, 2011 · Viewed 22.7k times · Source

I am using the following code:

#include <iostream>
using namespace std;

int main(int argc, char **argv) {
    string lineInput = " ";
    while(lineInput.length()>0) {
        cin >> lineInput;
        cout << lineInput;
    }
    return 0;
}

With the following command: echo "Hello" | test.exe

Thes result is an infinate loop printing "Hello". How can I make it read and print a single "Hello"?

Answer

Erik picture Erik · Mar 27, 2011 
string lineInput;
while (cin >> lineInput) {
  cout << lineInput;
}

If you really want full lines, use:

string lineInput;
while (getline(cin,lineInput)) {
  cout << lineInput;
}

Related questions

Detect if stdin is a terminal or pipe?

When I execute "python" from the terminal with no arguments it brings up the Python interactive shell. When I execute "cat | python" from the terminal it doesn't launch the interactive mode. Somehow, without getting any input, it has detected that …

Read More
How to make a pipe in c++

I'm looking at the code for a c++ program which pipes the contents of a file to more. I don't quite understand it, so I was wondering if someone could write pseudocode for a c++ program that pipes something to …

Read More
Pipe an input to C++ cin from Bash

I'm trying to write a simple Bash script to compile my C++ code, in this case it's a very simple program that just reads input into a vector and then prints the content of the vector. C++ code: #include <…

Read More