C / C++ / MFC

Garbled output using cerr in piped programs

3-Apr-06 9:09

Try:

AfxBeginThread(ThreadProc, this);
...
UINT CScanDlg::ThreadProc( LPVOID pParam )
{
    CScanDlg *pDlg = (CScanDlg *) pParam;
 
    if (pDlg->wmi(strIP1))
        return 0;
    else
        return 1;
}

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

Re: AfxBeginThread

viperlogic3-Apr-06 9:33

viperlogic

3-Apr-06 9:33

thx, that worked

can explain why thou?

Stian Andre Olsen3-Apr-06 5:56

Stian Andre Olsen

3-Apr-06 5:56

Recently, I discovered that using cerr from console programs that are linked together by a pipe can produce garbled output. I have made two test programs that illustrate the problem. I have also made two programs that use fprintf and stderr instead of cerr -- and the output is fine. Does anyone know how to avoid the garbled output (see below) while still using cerr?

The first two programs that use cerr for log messages are called StdOutCpp and StdInCpp. When executing the command "StdOutCpp | StdInCpp" I get the following output (varies a little bit from execution to execution):

StdOut: Printing to stdout...
StdOut: Printing byte 1...
StdOut: Byte 1 printed.
StdIn: Reading from stdin...
StdIn: Reading byte 1...
StdIn: Byte 1 read.
StdOut: Printing byte 250001...
StdOut: Byte 250001 pStdIn: Rrinted.
eading byte 250001...
StdIn: Byte 250001 read.
StdOut: Printing byte 500001...
StdOut: Byte 500001 pStdIrinted.
n: Reading byte 500001...
StdIn: Byte 500001 read.
StdOut: Printing byte 750001...
StdOut: Byte 750001 pStdrinted.
In: Reading byte 750001...
StdIn: Byte 750001 read.
StdOut: Finished printing to stdout.
StdIn: Finished reading from stdin.

As you can see from the above printout, some lines are mixed together.

The next two programs that use fprintf and stderr for log messages are called StdOutC and StdInC. When executing the command "StdOutC | StdInC" I get the following output:

StdOut: Printing to stdout...
StdOut: Printing byte 1...
StdOut: Byte 1 printed.
StdIn: Reading from stdin...
StdIn: Reading byte 1...
StdIn: Byte 1 read.
StdOut: Printing byte 250001...
StdOut: Byte 250001 printed.
StdIn: Reading byte 250001...
StdIn: Byte 250001 read.
StdOut: Printing byte 500001...
StdOut: Byte 500001 printed.
StdIn: Reading byte 500001...
StdIn: Byte 500001 read.
StdOut: Printing byte 750001...
StdOut: Byte 750001 printed.
StdIn: Reading byte 750001...
StdIn: Byte 750001 read.
StdOut: Finished printing to stdout.
StdIn: Finished reading from stdin.

A perfect output, exactly as I want it.

Code listings:

--- StdOutCpp.cpp begin ---
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
int n = 1000000;
cerr << "StdOut: Printing to stdout..." << endl;
for (int i = 0; i < n; i++)
{
if (i % (n / 4) == 0) cerr << "StdOut: Printing byte " << i+1 << "..." << endl;
cout << 'A';
if (i % (n / 4) == 0) cerr << "StdOut: Byte " << i+1 << " printed." << endl;
}
cerr << "StdOut: Finished printing to stdout." << endl;
return 0;
}
--- StdOutCpp.cpp end ---

--- StdInCpp.cpp begin ---
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
int n = 1000000;
cerr << "StdIn: Reading from stdin..." << endl;
for (int i = 0; i < n; i++)
{
if (i % (n / 4) == 0) cerr << "StdIn: Reading byte " << i+1 << "..." << endl;
cin.get();
if (i % (n / 4) == 0) cerr << "StdIn: Byte " << i+1 << " read." << endl;
}
cerr << "StdIn: Finished reading from stdin." << endl;
return 0;
}
--- StdInCpp.cpp end ---

--- StdOutC.cpp begin ---
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
int n = 1000000;
fprintf(stderr, "StdOut: Printing to stdout...\n");
for (int i = 0; i < n; i++)
{
if (i % (n / 4) == 0) fprintf(stderr, "StdOut: Printing byte %i...\n", i+1);
cout << 'A';
if (i % (n / 4) == 0) fprintf(stderr, "StdOut: Byte %i printed.\n", i+1);
}
fprintf(stderr, "StdOut: Finished printing to stdout.\n");
return 0;
}
--- StdOutC.cpp end ---

--- StdInC.cpp begin ---
#include <iostream>
using namespace std;

int main(int argc, char* argv[])
{
int n = 1000000;
fprintf(stderr, "StdIn: Reading from stdin...\n");
for (int i = 0; i < n; i++)
{
if (i % (n / 4) == 0) fprintf(stderr, "StdIn: Reading byte %i...\n", i+1);
cin.get();
if (i % (n / 4) == 0) fprintf(stderr, "StdIn: Byte %i read.\n", i+1);
}
fprintf(stderr, "StdIn: Finished reading from stdin.\n");
return 0;
}
--- StdInC.cpp end ---

Stian

STL next_permutation

thepersonof3-Apr-06 5:11

thepersonof

3-Apr-06 5:11

Hi I've the following code to generate permutations of my vector v:

<br />
		while (next_permutation(v.begin(), v.end() ) ) { <br />
                    // Loop until all permutations are generated.<br />
		copy(v.begin(), v.end(), ostream_iterator<int>(cout, ""));

How can I make it output to a vector instead?
I know I need to change to ostream_iterator, but what to?

cheers

-- modified at 11:14 Monday 3rd April, 2006

Re: STL next_permutation

Taka Muraoka3-Apr-06 5:23

Taka Muraoka

3-Apr-06 5:23

back_inserter

0 bottles of beer on the wall, 0 bottles of beer, you take 1 down, pass it around, 4294967295 bottles of beer on the wall.

Awasu 2.2 [^]: A free RSS/Atom feed reader with support for Code Project.

InitThunk

HakunaMatada3-Apr-06 3:14

HakunaMatada

3-Apr-06 3:14

What does the CAuxThunk and CAuxStdThunk classes do? What purpose does InitThunk have and why do we have to pass a Procedure name to it? What does TMPF stand for and what does it do?

Thanks... Smile | :)

---
With best regards,
A Manchester United Fan

The Genius of a true fool is that he can mess up a foolproof plan!

Hot toconnect databases to dialog based project

swapna_signsin3-Apr-06 3:00

Re: Hot toconnect databases to dialog based project

3-Apr-06 3:00

Hi friends,
I've done a project which is dialog based application.Now I need to connect databases.So how do I proceed now.Do Ineed to redo the whole project in SDI.Pls help me in solving this problem.

bye

swapna_signsin

Waldermort3-Apr-06 3:05

Waldermort

3-Apr-06 3:05

What sort of database are you trying to connect to?

Re: Hot toconnect databases to dialog based project

swapna_signsin3-Apr-06 4:05

Re: Hot toconnect databases to dialog based project

3-Apr-06 4:05

MSACCESS

thatsme_cool3-Apr-06 3:07

thatsme_cool

3-Apr-06 3:07

I don't think so
In order to connect to Data base visit this link
http://www.codeproject.com/database/connectionstrings.asp[^]

Re: Hot toconnect databases to dialog based project

David Crow3-Apr-06 3:56

Re: How toconnect databases to dialog based project

3-Apr-06 3:56

swapna_signsin wrote:
Now I need to connect databases.So how do I proceed now.

If you already have a DSN created, just derive a class from CRecordset using ClassWizard (Ctrl+W).

swapna_signsin wrote:
Do Ineed to redo the whole project in SDI.

No, not at all.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

swapna_signsin3-Apr-06 4:17

Re: How toconnect databases to dialog based project

3-Apr-06 4:17

Thanx for the reply,
but how do u create a DSN in Dialog based application.I mean how do u make use of ODBC Connection,bcoz u don't have a document/view when u'r using dialog based.

David Crow3-Apr-06 4:39

3-Apr-06 4:39

swapna_signsin wrote:
but how do u create a DSN

Use SQLConfigDataSource().

swapna_signsin wrote:
I mean how do u make use of ODBC Connection...

CRecordset handles the details for you. Just derive a class from it.

swapna_signsin wrote:
...u don't have a document/view when u'r using dialog based.

Whether you use document/view or not is irrelevant.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

How do u connect to DSN

swapna_signsin3-Apr-06 4:34

3-Apr-06 4:34

HI,
Actually Iam a beginner,Sorry to trouble u again,So how do u connect to DSN in Dialog Based applications,bcoz u don't have a Doc/View in this and u can't connect ODBC thru that.I've to connect to MSACCESS database.

Pls do reply,
bye

swapna_signsin

David Crow3-Apr-06 4:45

3-Apr-06 4:45

swapna_signsin wrote:
So how do u connect to DSN in Dialog Based applications...

In exactly the same way you would in any other application.

swapna_signsin wrote:
I've to connect to MSACCESS database.

After you've got a DSN created (see here for an example), use ClassWizard to derive a class from CRecordset.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

swapna_signsin3-Apr-06 5:24

3-Apr-06 5:24

Hi again,
I've tried it and I get the following errors :

1. 'CRecordSet' is not a class or a namespace namefor foll code: CRecordset::Dump(dc);
CRecordset::AssertValid();
2.'CFieldExchange':Undeclared Identifier
3.'CDatabase': Undeclared Identifier
and many of taht sort.

swapna_signsin

David Crow3-Apr-06 5:28

3-Apr-06 5:28

You failed to include afxdb.h.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

swapna_signsin3-Apr-06 5:54

3-Apr-06 5:54

Thanx,I'll try it and reply soon.

bye

swapna_signsin

PostNcDestroy() question

ns3-Apr-06 2:57

3-Apr-06 2:57

I have

CDialog::PostNcDestroy();

m_pParentWnd->SendMessage(UDM_LISTCLOSED,0,0);

delete this;

and in the .h file

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CTargetInfo)
	public:
	virtual BOOL OnInitDialog(); // called first time after construct

	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	virtual void PostNcDestroy();

	//}}AFX_VIRTUAL

The dialog was created by:

if(!m_tgtInfo)
{
    m_tgtInfo = new CTargetInfo(this, caseStudy);
    if(!m_tgtInfo) return true;
    m_tgtInfo->Create(IDD_DLGTGTINFO, (CWnd*)this);
    m_tgtInfo->ShowWindow(SW_SHOW);
}

When I close this modeless dialog, execution does not enter the PostNcDestroy function. However if I close the whole app, then the code does go into this function. What am I missing? I looked at sample code and there does not seem to be anything else I need to do... Confused | :confused:

thanks,
sb

-- modified at 9:00 Monday 3rd April, 2006

David Crow3-Apr-06 3:54

3-Apr-06 3:54

ns wrote:
CDialog::PostNcDestroy();
delete this;

Switch these two statements.

ns wrote:
When I close this modeless dialog, execution does not enter the PostNcDestroy function.

Have you called m_tgtInfo->DestroyWindow()?

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

ns3-Apr-06 4:00

3-Apr-06 4:00

When am I supposed to call m_tgtInfo->destroyWindow()? The user closes m_tgtInfo at which point I was trying to send a message to the parent (which instantiated m_tgtInfo)
thanks for helping,
sb

David Crow3-Apr-06 4:35

3-Apr-06 4:35

ns wrote:
When am I supposed to call m_tgtInfo->destroyWindow()?

When you want to dismiss the modeless dialog.

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb

ns3-Apr-06 4:41

3-Apr-06 4:41

A miscommunication, I think.
The user closes the m_tgtInfo dialog using the system menu at the upper right corner (the cross). I don't dismiss it with code. Am I still missing your point? When the cross is clicked, I thought the postNcDestroy() function would run, but it doesn't. Thanks for your patience.
sb

David Crow3-Apr-06 5:16

3-Apr-06 5:16

Do you have the following:

void CTargetInfo::OnOK()
{
    DestroyWindow();
}
 
void CTargetInfo::OnCancel()
{
    DestroyWindow();
}
 
void CTargetInfo::OnClose()
{
    DestroyWindow();
}

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb