C / C++ / MFC

• read return value is -1.
• read return value is positive, but less than 50.

while ( ! finished )
{
  ssize nread = read(fd[0],buf,50);
  if ( nread == -1 )
  {
    // handle error
  }
  else if (nread > 0)
  {
    printf("Read %d characters\n", nread);
    buf[nread]='\0';
    printf(buf);
    write(fileOpen, buf, nread);
  }
}

CPallini wrote:

For instance


while ( ! finished )
{
ssize nread = read(fd[0],buf,50);
if ( nread == -1 )
{
// handle error
}
else if (nread > 0)
{
printf("Read %d characters\n", nread);
buf[nread]='\0';
printf(buf);
write(fileOpen, buf, nread);
}
}

CPallini wrote:

where finished is a termination condition (timeout?) that you possibly know better than me.

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(int argc, char* argv[])
{
	if (argc != 5)
	{
		printf("Error!\nUsage: %s <input file 1> <input file 2> <input file 3> <output file>\n", argv[0]);
		return -1;
	}
	
	int fd[2];
	int fileOpen;
	int i;
	char buf[51];
	pipe(fd);	
	ssize_t nread;
	int count = 0;

	for (i=1; i < 4; i++)
	{
		switch (fork())
		{
		case -1:
			printf("Error: fork failure.\n");
			return -2;
		case 0:
			close(fd[0]); //child only writes to pipe
			printf("Child %d created. File: %s\n", i ,argv[i]);
			if ((fileOpen = open(argv[i], O_RDONLY)) == -1)
			{
				printf("File %s does not exist.\n", argv[i]);
				return -3;
			}
			printf("Child %d writing to pipe\n",i);
			while ((nread = read(fileOpen,buf,50)) > 0)
			{
				buf[nread] = '\0';
				printf("Child %d. Text: %s\n", i, buf);
				write(fd[1], buf, nread);
				usleep(25000*(rand()%8+3));
			}
			close(fd[1]); //child done writing
			close(fileOpen);
			printf("Child %d done writing to pipe\n",i);
			return 0;
		default:
			break;
		}
	}
	// father	
	close(fd[1]); //father only reads from pipe
	if ((fileOpen = open(argv[4],O_WRONLY|O_CREAT)) == -1)
	{
		printf("Unable to open file %s.\n", argv[4]);
		return -4;
	}
	printf("Father reading from pipe.\n");
	while (count < 1000)
	{
		if ((nread = read(fd[0],buf, 50)) > 0)
		{
			int i;
			printf("Father read line...\n");
			buf[nread] = '\0';
			printf("\n%s\n",buf);
			write(fileOpen, buf, nread);
		}
		else
		{
			printf("Father waiting for data...\n");
			usleep(10000);
		}
		count++;
	}
	close(fd[0]);
	close(fileOpen);
	printf("Father Done reading!\n");
		
	return 0;
}

SummerBulb wrote:

Here is my Code:

	int pids[3];
	int i;
//...
	for (i=1; i < 4; i++)
	{
		switch ((pids[i] = fork()))

sashoalm wrote:

I tried searching in google, but I couldn't find anything good.

Anu_Bala wrote:

error C3352: 'OnCallClick' : the specified function does not match the delegate type 'void (System::String ^)'

Maxwell Chen wrote:

(System::String ^ ) in the prototype is C# syntax, not C++.

N a v a n e e t h wrote:

It is not C#, it is C++/CLI.

Anu_Bala wrote:

static void OnCallClick(CString msg)
{
}

static void OnCallClick(System::String^ msg)<br />
{<br />
}

// CMainDlg dialog

class CMainDlg : public CDialog
{
// Construction
public:
	CMainDlg(CWnd* pParent = NULL); // standard constructor

	void BoxDone();

// Dialog Data
	//{{AFX_DATA(CMainDlg)
	enum { IDD = IDD_MAIN_DIALOG };
		// NOTE: the ClassWizard will add data members here
	//}}AFX_DATA

	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CMainDlg)
	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	//}}AFX_VIRTUAL

// Implementation
protected:
	HICON m_hIcon;
	<big>CAdderDialog* m_pModeless;</big>

	// Generated message map functions
	//{{AFX_MSG(CMainDlg)
	virtual BOOL OnInitDialog();
	afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
	afx_msg void OnPaint();
	afx_msg HCURSOR OnQueryDragIcon();
	virtual void OnOK();
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
public:
	afx_msg void OnBnClickedOk();
};