How to get the input and output in c++ using the < and > commands?

Question

I'm having a problem to find information about what these command does, what do they return and how to get them on my application in c++. That's an exercise and this is how I need to get the input file I'll be reading from and the output file I'll writing to:

myApp < input.txt > output.txt

I tried to access it using:

int main(int argc, char** argv){
   cout << argv[1] << endl;
}

But I didn't get anything back. I suspect that the argv[1] is an ifstream or something like that. What is it? Or it comes to my main function as a simple string? Should I receive more parameters on int main to get the "<" and ">" as files?

The answer suggested doesn't solve my problem. I wanted to know how the < and > commands work and the link suggested shows how to use piped cin and cout. Now I know it's a piped cin and cout, but I didn't know how the command line worked and linked to that.

Thank you!

On my application I'm already reading and writing to a file like this. But instead of having like std::string filename = "Test.b";, when I start the application I need to pass the files as arguments. Like this: myApp < input.txt > output.txt — Paloma Schkrab
– Paloma Schkrab, Commented Nov 6, 2018 at 6:14

Swordfish · Accepted Answer · 2018-11-06 06:13:32Z

4

With myApp < input.txt > output.txt you redirect stdin to be read from input.txt and stdout to write to output.txt. So you handle input and output just like you would if a console was attached to your program.

answered Nov 6, 2018 at 6:13

Swordfish

13.2k3 gold badges24 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Paloma Schkrab Over a year ago

Hmmm! So if I do a cout << "test" << endl; it will go to the output.txt file?

Swordfish Over a year ago

@PalomaSchkrab It should, yes.

Bardi Harborow · Accepted Answer · 2018-11-06 06:20:22Z

3

argv contains command line arguments. < input.txt is part of the shell syntax and pipes the contents of the file to standard input instead. If you want to read from that, you're looking for cin.

edited Nov 6, 2018 at 6:20

answered Nov 6, 2018 at 6:13

Bardi Harborow

1,9382 gold badges28 silver badges41 bronze badges

Collectives™ on Stack Overflow

How to get the input and output in c++ using the < and > commands?

2 Answers 2

2 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related