Reading text files from command prompt

Question

I want to be able to read text files from the command line. So what I'm trying to do is

1) ./a.out menu1.txt menu2.txt

And let the user choose how many files they want to read from so it could also be

2) ./a.out menu1.txt menu2.txt menu3.txt how do I do that?

menu1.txt 
hamburger 5.00
pizza 3.25
chips 2.50

menu2.txt
hamburger 2.00
pizza 2.35
chips 1.50

menu3.txt
hamburger 4.00
pizza 5.35
chips 0.50

This is what I have so far:

 #include <fstream>
 int main(int argc,  char *argv)
 {
  ifstream inStream; 

  for (int i = 1; i < argc; i++) {

    String menu1 = *argv[i]; 
    String menu2 = *argv[i]; 
    String menu3 = * argv[i]; 
    cout << i << " " << endl;  

}

}

Then go for it and try reading the files :) - you have the loop ready — Dusteh, Feb 18 '17 at 23:42
Your book should tell you how to use an `ifstream`. You do have a [good book](http://stackoverflow.com/a/388282/7455774), right? — Greg Kikola, Feb 18 '17 at 23:44

Stephan Lechner · Answer 1 · 2017-02-19T00:06:52.050

0

Function main provides the number of command line arguments and the argument values (including the name of the program itself): With that, you can achieve what you want.

#include <iostream>

int main( int argc, char* argv[] )
{
    std::cout << "The name used to start the program: " << argv[ 0 ]
    << "\nArguments are:\n";
    for (int n = 1; n < argc; n++)
        std::cout << n << ": " << argv[ n ] << '\n';
    return 0;
}

For more details, confer, for example, cppreference - main function. It explains, for example, that the "name of the program" could be an empty string:

argv[0] is the pointer to the initial character of a null-terminated multibyte strings that represents the name used to invoke the program itself (or an empty string "" if this is not supported by the execution environment)

edited Feb 19 '17 at 00:06

answered Feb 18 '17 at 23:43

Stephan Lechner

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Caveat: `std::cout << "The name used to start the program: " << argv[ 0 ]` is not entirely true. There will be an `argv[ 0 ]`, but it may be left blank. – user4581301 Feb 18 '17 at 23:59
@user4581301: Thanks for pointing that out. Adapted the answer accordingly. – Stephan Lechner Feb 19 '17 at 00:07

mpiatek · Answer 2 · 2017-02-18T23:53:24.093

You've got it mostly done.

You have bad signature of your main - that shold be int main(int argc, char** argv) or int main(int argc, char* argv[])
I don't understand why you try to initialize menu1, menu2 and menu3 with the same argument.

You may store your file paths in some std::vector<std::string> for future use.

#include <string>
#include <vector>

int main(int argc, char** argv)
{
    std::vector<std::string> filePaths;
    for (int i = 1; i < argc; ++i) {
        filePaths.emplace_back(argv[i]);
    }

    //...

    return 0;
}

Reading text files from command prompt

2 Answers2