Command Prompt Shell

I know it will sound weird at first, but I am trying to make a sort of wrapper around the Windows Command Prompt. The reason for this being that my school blocks windows' Command Prompt (and for good reason, some of the kids don't know squat about computers, and could really screw things up).

Here's what I have so far:

Code:

---

/*

Wrapper around the microsoft terminal.

Useful for when shell work is not available or disabled.

*/



// Includes start here...

#include <windows.h>

#include <stdlib.h>

#include <iostream>

#include <string>

// Includes end here...



// Tell that were gonna use some namespaces here...

using namespace std;



int main()

{

        bool                quit                = false;

        string                cwd        = "> ";

        string      quitstr1    = "quit";

        string      quitstr2    = "Quit";

        string                gettext;



        // Lets get the user name for nice display at the start of each line...

    char        currentuser[50];

    DWORD      ncurrentuser  = sizeof(currentuser);



    GetUserName(currentuser, &ncurrentuser);



    start:



        while(quit == false)

        {

                gettext = "";

                cout        << currentuser << cwd;

                cin                >> gettext;

                cin.ignore();



        if(gettext == quitstr1 || gettext == quitstr2)

        {

            quit = true;

            goto start;

        }



                system(gettext.c_str());

        }



        return 0;

}

---

I know this isn't quite the best solution, but it is a quick hack-up that will hopefully work when I try and use portable gcc at the schools computers (among other things that need the terminal).

My question is...

I want to give the program the ability to use the cd command. And what I'm thinking for this, is just to see if the user inputted 'cd C:\whatever', like I did with quit. Problem is, how to I just collect the first two characters, to see if it's 'cd'? And even if I do this, how to I collect everything after the third character (everything after 'cd<space>')? If I can just do this, I'll be able to append that path to './whatever.txt' files, so that the user doesn't always have to use full path names.

Thanks so much!
FlyingIsFun1217

Quote:

---

Problem is, how to I just collect the first two characters, to see if it's 'cd'?

---

It seems to me that locating the first whitespace character would be a better solution, after which you can take the substring based on that. std::string makes this easy.

By the way, there is no need to use goto in your program. Use a loop.

Quote:

---

Originally Posted by laserlight

By the way, there is no need to use goto in your program. Use a loop.

---

Or in this case use break.

Quote:

---

Originally Posted by laserlight

By the way, there is no need to use goto in your program. Use a loop.

---

I figure the code is small enough and not too horribly public, so I don't see why using a goto would be a bad idea.

I can search around easy enough to find how to find the first whitespace, but what exactly do you mean by 'taking the substring based on that'? Find the whitespace, and check to see what is before/after it?

Thanks again!
FlyingIsFun1217

Quote:

---

Originally Posted by FlyingIsFun1217

I figure the code is small enough and not too horribly public, so I don't see why using a goto would be a bad idea.

---

many code does start small and "not too horribly public". and then it grows. and then nobody has time to clean it up and nobody want to throw it away. And some rainy day some poor programmer writes a desperated post to this board about how to fix the messed up spaghetti-goto program he should maintain because the creator is to busy writing new spaghetti code elsewhere. just do it right. you won't lose anything

Quote:

---

Originally Posted by FlyingIsFun1217

I can search around easy enough to find how to find the first whitespace, but what exactly do you mean by 'taking the substring based on that'? Find the whitespace, and check to see what is before/after it?

Thanks again!
FlyingIsFun1217

---

Code:

---

if
(
    yourString.substring(0, yourString.find(string(" ")))
    ==
    string("cd")
)
{
  // you got  a string starting with "cd"
}

---

Quote:

---

Originally Posted by pheres

many code does start small and "not too horribly public". and then it grows. and then nobody has time to clean it up and nobody want to throw it away. And some rainy day some poor programmer writes a desperated post to this board about how to fix the messed up spaghetti-goto program he should maintain because the creator is to busy writing new spaghetti code elsewhere. just do it right. you won't lose anything

---

I mean for this to be a mostly personal project, and I'm sure that the code is so messed up anyway, that I would hope others DON'T use it. But alas, to fall into peer pressure and clean up code, I will use a break.

Quote:

---

Originally Posted by pheres

Code:

---

if
(
    yourString.substring(0, yourString.find(string(" ")))
    ==
    string("cd")
)
{
  // you got  a string starting with "cd"
}

---

---

Very helpful! Guess I better have looked over my reading better.
I will read through my C++ book, but... and this is why I am going to read through my book, because it will sound kinda rude... how would I best be able to get the path from the user? Would it be to look for the fourth entry?

FlyingIsFun1217

Code:

---

string path;
string::size_type first_space = yourString.find(string(" "));
if
(
    yourString.substring(0, first_space)
    ==
    string("cd")
)
{
  // you got  a string starting with "cd"
  // now get the path
  path = yourString.substring(first_space);

  // now take the path string and break it into it's components.
  // therefore search for "\" or "/"
  // depending on your system
  // ...left to the reader ;)
}

---

just written out of my head.
http://www.sgi.com/tech/stl/basic_string.html
will help you

Quote:

---

Originally Posted by FlyingIsFun1217

I figure the code is small enough and not too horribly public, so I don't see why using a goto would be a bad idea.

---

You don't write maintainable code to avoid being embarrassed in public. You write maintainable code because it's maintainable.

Quote:

---

Originally Posted by CornedBee

You don't write maintainable code to avoid being embarrassed in public. You write maintainable code because it's maintainable.

---

I don't plan on maintaining this when I'm done ;)

Thanks for the example, and especially the link!

FlyingIsFun1217

>> I don't plan on maintaining this when I'm done

Of course, the other reason to write maintainable code is to get in the habit of doing it for the time when you do plan on maintaining your code.

Quote:

---

Originally Posted by Daved

>> I don't plan on maintaining this when I'm done

Of course, the other reason to write maintainable code is to get in the habit of doing it for the time when you do plan on maintaining your code.

---

Very true...

FlyingIsFun1217

Hola amigos!

Here's my current code:

Code:

---

/*
Wrapper around the microsoft terminal.
Useful for when shell work is not available or disabled.
*/

// Includes start here...
#include <windows.h>
#include <stdlib.h>
#include <iostream>
#include <string>
// Includes end here...

// Tell that were gonna use some namespaces here...
using namespace std;

int main()
{
        bool                quit                = false;
        string                cwd        = "> ";
        string      quitstr1    = "quit";
        string      quitstr2    = "Quit";
        string                gettext;

        // Lets get the user name for nice display at the start of each line...
    char        currentuser[50];
    DWORD      ncurrentuser  = sizeof(currentuser);

    GetUserName(currentuser, &ncurrentuser);

        while(quit == false)
        {
                gettext = "";
                cout        << currentuser << cwd;
                cin                >> gettext;
                cin.ignore();

        if(gettext == quitstr1 || gettext == quitstr2)
        {
            quit = true;
            break;
        }

        // Check for 'CD...', give a string containing first two letters...
        string cdstring = gettext.substr(0,2);
        // Conditional strings to check for 'CD', 'Cd', 'cD', 'cd',...
        string cd1 = "CD";
        string cd2 = "Cd";
        string cd3 = "cD";
        string cd4 = "cd";
        // Store current directory in this string. ABSOLUTE DEFINITIVE DIRECTORY HOLDER!
        string currentdirectory = "";

        if(cdstring == cd1 || cdstring == cd2 || cdstring == cd3 || cdstring == cd4)
        {
            string tempdirectory = gettext.substr(3,65);
            currentdirectory = tempdirectory;

            tempdirectory.erase(0,tempdirectory.length());
        }

                system(gettext.c_str());
        }

        return 0;
}

---

Seems though that when I type in at my 'shell': cd <whateverhere>, I just get an unexpected error, reported when running through C::B as:

Quote:

---

This application has requested the Runtime to terminate it in an unusual way. Please contact the applications support team for more information.

---

Running it standalone though just gives me the result of the program instantaneously closing.

Any thoughts on this one?
FlyingIsFun1217

substr() asserts (or even throws, not sure) if any index is out of range. Your generous (3, 65) substring is probably out of range most of the time.

Surely there is a way to compare strings in a case-insensitive way - if nothing else, create a lower or upper case copy of your string, and compare it to your command - imagine the number of combinations of "mkdir" (32 combinations) or "delete" (64 combinations) for example - you'd be forever writing command comparisons.

The other thought on this subject is that you probably want to create a structure/class with command and function pointers to make the parsing and implementation of new commands easier. You may also want to take your input string and split it at spaces into a int argc, char *argv[] set. That way, you can easily sort out things like "rmdir /s directory-to-delete" [well, at least it's EASIER than if in each command you go about splitting the string into pieces].

--
Mats

Quote:

---

Originally Posted by matsp

Surely there is a way to compare strings in a case-insensitive way - if nothing else, create a lower or upper case copy of your string, and compare it to your command - imagine the number of combinations of "mkdir" (32 combinations) or "delete" (64 combinations) for example - you'd be forever writing command comparisons.

The other thought on this subject is that you probably want to create a structure/class with command and function pointers to make the parsing and implementation of new commands easier. You may also want to take your input string and split it at spaces into a int argc, char *argv[] set. That way, you can easily sort out things like "rmdir /s directory-to-delete" [well, at least it's EASIER than if in each command you go about splitting the string into pieces].

--
Mats

---

Still doesn't explain my current error though, which is what I'm most interested in at the moment...

Good tips though, I will definitely split it up into separate functions soon :)

FlyingIsFun1217

>> Still doesn't explain my current error though, which is what I'm most interested in at the moment...
Did fixing the substr call help?

>> tempdirectory.erase(0,tempdirectory.length());
BTW, this line does nothing important. The variable is about to go out of scope anyway, and if you wanted to clear a string you should use clear().

Quote:

---

Originally Posted by matsp

You may also want to take your input string and split it at spaces into a int argc, char *argv[] set. That way, you can easily sort out things like "rmdir /s directory-to-delete"

---

Not to sound to braindead, but could you show an example of how to do this? If anything, just don't give me a straight example, I wanna figure it out myself ;)

FlyingIsFun1217

Quote:

---

Originally Posted by FlyingIsFun1217

Still doesn't explain my current error though, which is what I'm most interested in at the moment...

Good tips though, I will definitely split it up into separate functions soon :)

FlyingIsFun1217

---

Yes, that's true, and I didn't try to say anything about that, because as far as I was concerned, CornedBee seemed to have already answered that.

--
Mats

Quote:

---

Originally Posted by FlyingIsFun1217

Not to sound to braindead, but could you show an example of how to do this? If anything, just don't give me a straight example, I wanna figure it out myself ;)

FlyingIsFun1217

---

Well, if you have a line of input, with spaces [tabs may be separators too, if you like], scan through the line [or use "find" or "locate", whatever it is called] to find the spaces, and copy each portion into a separate string [I suggested char array, but I guess the better solution is to have an array of C++ style strings]. Give each function a number of strings and a pointer to the array of strings. So for example, the function to do "cd" would look like this:

Code:

---

int cd(int argc, string *argv)
{
    if (argc != 1) {
      cout << "Incorrect number of parameters for \"" << argv[0] << "\"\n";
      return 1;
    }
    res = chdir(argv[1]);
    if (!res) {
      cout << "Error, could not change to directory \"" << argv[1] << "\"\n";
    }
    return res;
}

---

This is untested code, so you may find that it doesn't work quite right - but it should give you an idea.

Note that argv[0] should be the command itself, so for example "cd foo" should give:

Code:

---

argv[0] = "cd";
argv[1] = "foo";
argc = 2;

---

--
Mats

Don't forget that argv[argc] must be valid and a null pointer.

Since I've only been coding in C++ for a year, in between school assignments, I haven't had great practice at it, and in this case, I believe arrays are what I really need to know better.

I'll look it up, and as usual, thanks for the awesome help!
FlyingIsFun1217