C / C++ / MFC

4-Jul-20 20:08

i'm just testing to run prog using parameters, but why i got error when debugging?

screenshot[^]

this is my code:

#include <iostream>

int main (int argc, char * argv []) {
	
	if (argc > 0) {
		std::cout << *argv[1] << std::endl;
	}

	std::cin.ignore(std::numeric_limits<int>::max(), '\n');
	std::cout << "press ENTER to close program.";
	std::cin.get();
	return 0;
}

Richard MacCutchan4-Jul-20 21:09

4-Jul-20 21:09

If you call the program via:

myprog.exe

then argc will equal 1, and argv[1] will not exist, hence the exception. Remember, array indexes start from zero, not one.

chipp_zanuff4-Jul-20 22:15

4-Jul-20 22:15

i know, but how to respond users if there's argument(s) submitted?

Richard MacCutchan4-Jul-20 22:19

4-Jul-20 22:19

You have two choices:
1. Your program needs specific argument values which you must check by iterating over the items in argv. The actual number and type is for you to decide.
2. Your program does not accept command line arguments in which case you just ignore them. You may wish to display a warning message if argc is greater than 1.

chipp_zanuff4-Jul-20 23:15

4-Jul-20 23:15

1. you mean like loop? i tried this but still error:

#include <iostream>

int main (int argc, char * argv []) {
	
	int itr = 0;

	if (argc > 0) {
		while (itr <= argc) {
			std::cout << argv[itr] << std::endl;
			++itr;
		}
	}

	std::cin.ignore(std::numeric_limits<int>::max(), '\n');
	std::cout << "press ENTER to close program.";
	std::cin.get();
	return 0;
}

2. so how to make my program accept argument(s)?

Richard MacCutchan5-Jul-20 0:11

5-Jul-20 0:11

You did not mention what error you received, but I assume it is because you are still trying to access an item which does not exist. The values for argc and argv are as follows:
1. argv is an array of strings, which will always contain at least one item: the name of the executable that is used to initiate the program.
2. argc contains the number of items in the argv array. So it will always be at least 1.

Let's look at a couple of examples:
1. A simple command line call to run my program, which is called Test.exe produces the following:

C:\Users\user1\Documents\Code\C++>Test.exe
argc = 1
argv[0] = Test.exe

There are no input parameters, argc equals 1 as there is only one item in argv, and that is argv[0] which contains the program name. If I use the full path to run the program the output will be:

C:\Users\user1\Documents\Code\C++>C:\Users\user1\Documents\Code\C++\Test
argc = 1
argv[0] = C:\Users\user1\Documents\Code\C++\Test

If we add some parameters to the command line we will get something like

C:\Users\user1\Documents\Code\C++>Test.exe one two "three and a half"
argc = 4
argv[0] = Test.exe
argv[1] = one
argv[2] = two
argv[3] = three and a half

So argv now contains 4 items, the program name followed by each item that is separated by a space or tab. Not that argv[3] contains four words, since they were delineated by double quotes in the command line.

The code to list these values is as follows:

std::cout << "argc = " << argc << std::endl;
for (int i = 0; i < argc; ++i)
{
    std::cout << "argv[" << i << "] = " << argv[i] << std::endl;
}

Generally you are not interested in the program name so you can start the above loop from 1 rather than 0.

The actual values in each parameter are for you to decide. You can use simple strings in a specific or random order, option letters or names preceded by single or double dashes or forward slashes:

Test check \foo\bar\filename.txt
Test -c C:\user1\Documents\file.jpg
Test --check somefilename

... etc.

chipp_zanuff5-Jul-20 6:17

5-Jul-20 6:17

this is really embarrassing! this was my mistake...

thank you very much! i just fix the code and now it's working![^]

this is the final test code:

#include <iostream>

int main (int argc, char * argv []) {

	if (argc > 1) {
		std::cout << argv[1] << std::endl;
	}

	std::cin.ignore(std::numeric_limits<int>::max(), '\n');
	std::cout << "press ENTER to close program.";
	std::cin.get();
	return 0;
}

really appreciate your reply!!

Richard MacCutchan5-Jul-20 6:35

5-Jul-20 6:35

You are welcome.

python language

seotutorialszone4-Jul-20 10:40

seotutorialszone

4-Jul-20 10:40

what is best resource to learn python language

chipp_zanuff4-Jul-20 20:13

4-Jul-20 20:13

you know that this is C & C++ thread, right?

Richard MacCutchan4-Jul-20 21:06

4-Jul-20 21:06

seotutorialszone wrote:
what is best resource to learn python language

1. The ability to use your brain.
2. Google.
3. The Python Tutorial — Python 3.7.8 documentation[^]

modified yesterday.

Patrice T5-Jul-20 0:16

Patrice T

5-Jul-20 0:16

Try to Google with Python and tutorial.

Patrice

“Everything should be made as simple as possible, but no simpler.” Albert Einstein

Create C++ Program for Android Gaming

CPallini5-Jul-20 20:15

CPallini

5-Jul-20 20:15

The C/C++/MFC forum, of course. Big Grin | :-D

Message Closed

4-Jul-20 6:48

OnlyGame13

4-Jul-20 6:48

Message Closed

OnlyGame134-Jul-20 6:46

OnlyGame13

4-Jul-20 6:46

Can i Use C++ Progam to develop a Appliciton for Andriod?

Re: Create C++ Program for Android Gaming

Dave Kreskowiak4-Jul-20 6:56

Dave Kreskowiak

4-Jul-20 6:56

What happened when you Googled for "C++ application development"?

Asking questions is a skill
CodeProject Forum Guidelines
Google: C# How to debug code
Seriously, go read these articles.

Dave Kreskowiak

Re: Create C++ Program for Android Gaming

David Crow4-Jul-20 9:42

David Crow

4-Jul-20 9:42

Yes.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles

Re: Create C++ Program for Android Gaming

CPallini5-Jul-20 20:17

CPallini

5-Jul-20 20:17

Yes, though I am not sure it is the simplest path. Have a look at Android NDK | Android Developers[^].

Sir? Builtin Function Help

NaumanMalik26-Jun-20 9:08

NaumanMalik

26-Jun-20 9:08

Hi, How are you?...i hope you are doing fine... i want to ask is there any built in function to get on exact line in a file? Like:

FILE DATA:
1)Start
2)Mid
3)Username
4)END

i want to get the pointer of file handler on 3 so that i can read that specific line....
or Can we use Seekg.(); function in this case? Kindly help please

Robust Services Core | Software Techniques for Lemmings | Articles

Greg Utas26-Jun-20 10:47

Greg Utas

26-Jun-20 10:47

I don't know of such a function. If each line ends in an '\n', you can use std::getline to read each one and count up to the line you want.

seekg moves by a specified number of characters, so it won't help unless lines are padded to a fixed length.

Richard MacCutchan26-Jun-20 22:17

26-Jun-20 22:17

The simplest way to do this is to read the file line by line and check for the data that you are interested in. Remember a text file is just a stream of characters with no structure so you cannot easily use file positioning to get to a particular item.

Richard MacCutchan27-Jun-20 0:21

27-Jun-20 0:21

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