C / C++ / MFC

Re: How to use command line arguments in a win32 application?

14-Jul-08 21:14

Hi guys,

I am trying to implement some command-line arguments for my application. I would like to be able to run the program with "Program.exe -w800 -h600" to force the resolution to be displayed at 800*600.

I've come up with this basic code that I would have thought could achieve the goal I had in mind but I get the error

error C2446: '==' : no conversion from 'const char *' to 'int' There is no context in which this conversion is possible

So lpCmdLine is a pointer to a const char, so how do I extract the information I want from it? Wouldn't it have been easier for microsoft to just implement it as an array of char's? Frown | :(

WINDOW_WIDTH and WINDOW_HEIGHT are both global integers.

// Get command-line parameters
for (int n=0; n < (sizeof(lpCmdLine) / sizeof(char)); n++)
{
    if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "w")
    {
        char w[4];
        w[0] = lpCmdLine[n+2];
        w[1] = lpCmdLine[n+3];
        w[2] = lpCmdLine[n+4];
        w[3] = lpCmdLine[n+5];
        WINDOW_WIDTH = w[];
    }

    if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "h")
    {
        char h[4];
        h[0] = lpCmdLine[n+2];
        h[1] = lpCmdLine[n+3];
        h[2] = lpCmdLine[n+4];
        h[3] = lpCmdLine[n+5];
        WINDOW_HEIGHT = h[];
    }
}

The solution probably has something to do with some hefty use of pointers Frown | :(

Cedric Moonen14-Jul-08 21:26

Cedric Moonen

14-Jul-08 21:26

You should use atoi[^] if you want to convert a string (e.g. "800") into the corresponding integer.

Cédric Moonen
Software developer

Charting control [v1.4]
OpenGL game tutorial in C++

Re: How to use command line arguments in a win32 application?

Sauce!14-Jul-08 21:36

Re: How to use command line arguments in a win32 application?

14-Jul-08 21:36

sorry but I don't think that will work for my purposes Frown | :(

I need to be able to parse the string first for any - signs followed by either a w or h. Once I get that working then I would be able to use atoi to convert the numbers in the string but I can't get to that point using atoi Frown | :(

CPallini14-Jul-08 21:41

Re: How to use command line arguments in a win32 application?

14-Jul-08 21:41

Your code has several flaws.
Try

int iLen = _tcslen(lpCmdLine);
for (int i = 0; i < iLen - 2; i++) // supposing at least a digit following -h or -w option
{
  if ( lpCmdLine[i] == _T('-'))
  {
    if (lpCmdLine[i+1] == _T('h'))
    {
      WINDOW_HEIGHT = _tstoi(&(lpCmdLine[i+2]));
    }
    else if (lpCmdLine[i+1] == _T('w'))
    {
      WINDOW_WIDTH = _tstoi(&(lpCmdLine[i+2])); 
    }
  }
}

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Sauce!14-Jul-08 21:50

Re: How to use command line arguments in a win32 application?

14-Jul-08 21:50

It took me a few minutes to understand your code (had to search through all the help files for all that stuff I've never seen before)

It looks like it should work.

But it doesnt Frown | :(

error C2664: 'wcslen' : cannot convert parameter 1 from 'LPSTR' to 'const wchar_t *'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
error C2664: '_wtoi' : cannot convert parameter 1 from 'CHAR *' to 'const wchar_t *'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
error C2664: '_wtoi' : cannot convert parameter 1 from 'CHAR *' to 'const wchar_t *'
Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast

And could you please give me some hints as to why my code is flawed? I was already aware there was something wrong with it, hence the reason it doesn't work.

CPallini14-Jul-08 22:00

Re: How to use command line arguments in a win32 application?

14-Jul-08 22:00

OK. These errors arise because the LPSTR nature of lpCmdLine. Use:

int iLen = strlen(lpCmdLine);
for (int i = 0; i < iLen - 2; i++) // supposing at least a digit following -h or -w option
{
  if ( lpCmdLine[i] == '-')
  {
    if (lpCmdLine[i+1] == 'h')
    {
      WINDOW_HEIGHT = atoi(&(lpCmdLine[i+2]));
    }
    else if (lpCmdLine[i+1] =='w')
    {
      WINDOW_WIDTH = atoi(&(lpCmdLine[i+2])); 
    }
  }
}

Sauce!14-Jul-08 22:21

Re: How to use command line arguments in a win32 application?

14-Jul-08 22:21

thankyou, your code works flawlessly. Big Grin | :-D

Bloody legend :P

Now, may we discuss the bad things I did in my original snippet so that I may learn from it in the future? That would be nice Smile | :)

CPallini14-Jul-08 22:38

Re: How to use command line arguments in a win32 application?

14-Jul-08 22:38

Sauce! wrote:
Now, may we discuss the bad things I did in my original snippet so that I may learn from it in the future? That would be nice

Your original code:

// Get command-line parameters
	for (int n=0; n < (sizeof(lpCmdLine) / sizeof(char)); n++)
	{
		if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "w")
		{
			char w[4];
			w[0] = lpCmdLine[n+2];
			w[1] = lpCmdLine[n+3];
			w[2] = lpCmdLine[n+4];
			w[3] = lpCmdLine[n+5];
			WINDOW_WIDTH = w[];
		}

		if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "h")
		{
			char h[4];
			h[0] = lpCmdLine[n+2];
			h[1] = lpCmdLine[n+3];
			h[2] = lpCmdLine[n+4];
			h[3] = lpCmdLine[n+5];
			WINDOW_HEIGHT = h[];
		}
	}

1. sizeof(lpCmdLine) = sizeof(LPSTR) = 4 (on 32 bit systems). You should use strlen(lpCmdLine) instead.

2. Since the code inside the loop accesses lpCmdLine[n+5], the loop itself cannot run on the whole lpCmdLine's range available.
So the loop controlling condition should be (n < strlen(lpCmdLine) - 5) to
prevent buffer overrun.

3. You wrote your own version of atoi, but it is wrong: suppose pCmdLine[0] to pCmdLine[3] containing the right input for the number, the (brute force and simplified) code for a atoi-like function may be

int value = 0;
value = pCmdLine[0]-'0'; // since pCmdLine[0] is a character 
value *= 10;
value += pCmdLine[1]-'0';
value *= 10;
value += pCmdLine[2]-'0';
value *= 10;
value += pCmdLine[3]-'0';

Sauce!15-Jul-08 2:39

Re: How to use command line arguments in a win32 application?

15-Jul-08 2:39

1) Huh, missed that one completely. Probably could have been avoided if I could find some better documentation on the exact data-type and format of lpCmdLine. Microsoft's documentation was pretty poor. Frown | :(

2) thanks, I was wondering why you subtracted 2 from iLen in your example. I thought to myself "yeah, it's technically correct, but you don't need to do it" (what a stupid thing to think!) I didn't even think about preventing buffer overrun.

3) I'm not sure what you're getting at here...

CPallini15-Jul-08 3:15

Re: How to use command line arguments in a win32 application?

15-Jul-08 3:15

Sauce! wrote:
3) I'm not sure what you're getting at here...

Well, suppose:

lpCmdLine = "-w800";

this really means

lpCmdLine[0] = '-';
lpCmdLine[1] = 'w';
lpCmdLine[2] = '8';
lpCmdLine[3] = '0';
lpCmdLine[4] = '0';

Consider lpCmdLine[2] = '8'. Here lpCmdLine[2] is a char variable holding the ASCII value of the character '8' (that is 56 decimal). If you write

int iFirstDigit = lpCmdLine[2];

then you make a mistake, because iFirstDigit will contain 56 instead of 8. On the other hand, writing

int iFirstDigit = lpCmdLine[2] - '0';

you get the expected value (in a rather portable way), since numbers are ordered in the ASCII encoding following their natural (ordinal!) sequence, hence
lpCmdLine[2] - '0' = 56 - 48 = 8.
Now, suppose you make the same for the following digits, obtaining

iFirstDigit = 8; // please note, quite different with respect '8'!
iSecondDigit = 0;
iThirdDigit = 0;

to finally build the number you have to exploint the base 10 positional numbering system, i.e. poorly speaking:

int iNumber = iFrstDigit * 100 + iSecondDigit * 10 + iThirdDigit;

I made the above in a incremental way on previously posted code.
Smile | :)

Sauce!15-Jul-08 5:51

Re: How to use command line arguments in a win32 application?

15-Jul-08 5:51

You're so clever :]

Thankyou very much for your help. You've been quite informative Smile | :)

I've never fully understood converting from char's to int's, but you've cleared it all up for me Big Grin | :-D

CPallini16-Jul-08 7:04

Re: How to use command line arguments in a win32 application?

16-Jul-08 7:04

Sauce! wrote:
You're so clever :]

Thank you. Blush | :O

Sauce! wrote:
Thankyou very much for your help. You've been quite informative

I've never fully understood converting from char's to int's, but you've cleared it all up for me

You're welcome.
Smile | :)

David Crow15-Jul-08 3:21

David Crow

15-Jul-08 3:21

Sauce! wrote:
if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "w")
...
if(lpCmdLine[n] == "-" && lpCmdLine[n+1] == "h")

lpCmdLine[n] is a single character, yet you are comparing to an array of characters (even though there is only one character present). You should use single quotes instead, like:

if (lpCmdLine[n] == '-' && lpCmdLine[n+1] == 'w')

"Love people and use things, not love things and use people." - Unknown

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

How to verify that calling process has read access to the specified range of memory in vista

V K 214-Jul-08 20:33

V K 2

14-Jul-08 20:33

How to verify that calling process has read access to the specified range of memory in vista. Earlier IsBadReadPtr and IsBadWritePtr could be used. But it is not suggestible by Microsoft. Can I know any other alternate method to verify that calling process has access to memory

Thanks,
Venkat

Re: How to verify that calling process has read access to the specified range of memory in vista

Stephen Hewitt14-Jul-08 20:42

Re: How to verify that calling process has read access to the specified range of memory in vista

14-Jul-08 20:42

In almost all cases the professional thing to do is crash. Why are you so insistent on implementing what is almost certainly a bad idea? We’ve had this discussion before. If you can give a compelling reason why your application is an exception I’ll give you some pointers, but I’m reluctant to be a part of the spread of bad programming practices.

Steve

Stephen Hewitt14-Jul-08 20:53

fatal error: Cannot open type library file: 'msxml.dll' in Vista

14-Jul-08 20:53

I assume you just voted my reply down. If so, that's all well and good, but it doesn't change the facts. Again, see the following expert opinions on this issue:
Raymond Chen[^]: "You should crash."
Larry Osterman[^]

Steve

NiceNaidu14-Jul-08 19:48

NiceNaidu

14-Jul-08 19:48

Hi friends,
The following code is giving the above error.

#include  windows.h ;
#import msxml.dll ;
int main(int, char*[])
{
 return 0;
}

on vista.

I got a solution in msdn forums to replace the msxml.dll with msxml.tlb .Still i am getting the same error saying "Cannot open type library file: 'msxml.tlb':"
(http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=365059&SiteID=1[^]

Can someone tell me the reason for this.

Thanks in advance.

Appu..
"Never explain yourself to anyone.
Because the person who likes you does n't need it.
And the person who dislikes you won't believe it."

Re: fatal error: Cannot open type library file: 'msxml.dll' in Vista

Stephen Hewitt14-Jul-08 20:22

enable DHCP using win32 API

14-Jul-08 20:22

Documentation for #import can be found here[^]. The following table is a quote from the section entitled "Search Order for filename":

Syntax form	Action
Quoted form	Instructs the preprocessor to look for type library files first in the directory of the file that contains the #import statement, and then in the directories of whatever files that include (#include) that file. The preprocessor then searches along the paths shown below.
Angle-bracket form	Instructs the preprocessor to search for type library files along the following paths: 1. The PATH environment variable path list 2. The LIB environment variable path list 3. The path specified by the /I (additional include directories) compiler option

This should be enough for you to fix the problem.

Steve

an8914-Jul-08 19:45

an89

14-Jul-08 19:45

I have to write code for enabling DHCP using win32 API.can anybody help?I don't want WMI functions for this.Thanks....

Re: enable DHCP using win32 API

Stephen Hewitt14-Jul-08 20:36