Using variables within system command?

Hey guys, I'm not sure if what I'm trying to do is possible or the way I should do it. Basically I want to ask for a hostname, a message and place them in string variables as host and msg respectively. The contents will then be parsed onto the "net send" system command.

This is my best way of describing what I'm trying to do:

Code:

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system("net send ") << host << msg << endl;

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If its not clear enough I can post more of the code.

Put that into one string and then pass it to the system command.

Code:

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string systemSender = "net send ";

systemSender += host + msg;

system(systemSender.c_str());

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Though make sure to add spaces between the parameters.

How do you know it needs spaces ;). Maybe its comma sepeated :D

Because generally if a person is using 2 different varaibles for a command such as that, it will need spaces between them because they are sperate parameters. Though I could be wrong, I doubt that I am.

It was a joke(just making sure you know that).

I was just showing off my mind reading skills in my first post in this thread... then I had to back track so people didn't think I could read minds that way I don't get asked... "What am I thinking right now?!"

I got a compile error from Dev C++ telling me

Code:

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systemSender += host + msg;

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is wrong, so I changed it to

Code:

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systemSender += host, msg;

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and it compiles fine. Everything seems to be working fine except when I try "Host: 127.0.0.1" & "Msg: Hello" it tells me sending files are no longer supported. I think this is because the variables parsed mighten be spaced out after eachother, so its trying to perform this command:

Code:

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net send 127.0.0.1Hello

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How can I space host and msg out?

Well, what are host and msg defined as? If the are just char * or char[] then yes that won't work.

And to add a space you can make those strings and do this:

Code:

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systemSender += host + " " + msg;

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Commas are not the same as most languages and lists when in programming languages. I am supprised that worked as it did.

One thing you can do is

Code:

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string systemSender = "net send " + host + " " + msg;

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The +'s dont seem to work, I get an error on compile but I'll show you what does work.

Code:

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#include <iostream>
#include <dos.h>
#include <string>

using namespace std;

char host[64], msg[512];
string systemSender = "net send ";

char getinfo()
{
    cout<< "Hostname: ";
    cin.getline (host, 64, '\n');
    cout<< "Message: ";
    cin.getline (msg, 512, '\n');
}

char send()
{
    systemSender += host;
    systemSender += " ";
    systemSender += msg;
    system(systemSender.c_str());
}

int main()
{ 
    getinfo();
    send();
    cin.get();
}

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Anything I'm missing thats not letting me use "+ host + msg" ?

Yes like I said above the + operator isn't overloaded to take 2 char*'s which is what you are doing there.

So what can it take two of?

Quote:

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Originally Posted by moagim

Anything I'm missing thats not letting me use "+ host + msg" ?

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Yes, you cannot concatenate character strings like that. The + operator only works if one or both arguments are std::string.

Sweet everything works thanks

The program seems to run with just the iostream header file on its own, why arent the others required? Just curious

Due to the way the standard library is usually implemented, some standard headers include others internally, and thus the symbols from those other headers become available, too.
The important thing is that this is only a side effect, and a completely unpredictable at that. A different compiler, even a different standard library, might be implemented differently and make your program fail.

Code:

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#include <iostream>
#include <dos.h>
#include <string>

using namespace std;

int select;
string host, msg;
string systemSender = "net send ";



char getinfo()
{
    system("cls");
    cout<< "------------------------\n"
        << "Potato Net Sender v0.01\n"
        << "------------------------\n\n";
    cout<< "Hostname: ";
    cin>> host;
    cout<< "Message: "; 
    getline (cin, msg, '\n');
    cin>> msg;
}

char send()
{
    systemSender += host + " " + msg;
    system(systemSender.c_str());
}

char selection1()
{
            cin.get();
            getinfo();
            send();
}

int exit_app()
{
    return 0;
}

char intro()
{
    system("cls");
    cout<< "------------------------\n"
        << "Potato Net Sender v0.01\n"
        << "------------------------\n\n";
       
    cout<< "1. Send a message to another computer\n"
        << "2. Exit\n\n";
    cout<< "Selection: ";
    cin>> select;
   
    if (select == 1)
    {
            selection1();
    }   
    else if (select == 2)
    {
          exit_app();
    }
    else
    {
        system("cls");
        cout<< "\nYou must enter either 1 or 2 to proceed\n\n";
        cout<< "Press any key to try again...";
        cin.get();
        selection1();
    }
}

int main()
{ 
    intro();
    cin.get();
}

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Hmm I'm having another slight problem, possibly I'm using the wrong syntax for storing the string into variable msg.

Whenever I type a message with more than one word it will just net send the first word, it doesnt seem to be capturing the whole string.

For Example:

Code:

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Hostname: 127.0.0.1
Message: Hello this is a test

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That will send only "Hello" through net send.

That's probably because net send only sends its first argument. You must make sure quotes appear on the command line, i.e. the string you send to system.

Yeah but I want to be able to store what I type in the string without the quotes, isnt that possible?

[edit]
Doesnt work with quotes anyway

> systemSender += host + " " + msg;
> system(systemSender.c_str());
If you're just being hackish and using system() to do all the dirty work for you, then you need to be more careful with the command line you construct.

Say

Code:

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    systemSender += host + " \"" + msg + "\"";
    system(systemSender.c_str());

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to include the message you want to send in double quotes

What else could I use other than system() ? I use it cause its all I know so far, also, I dont quite understand that code you typed, and it gives me the same result as before

Does this work?

Code:

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system( "net send \"hello world\" ");

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> What else could I use other than system() ?
Like the proper sockets interface to write true networking applications.

You can basically do what you have at the moment using a batch file.