I was writing a program communicating via COMM with read/write, and thinking of setting the comm to synchronous mode, such that write() function won’t return until all data in the buffer has been sent. So, I tried to set the O_DSYNC flag by calling fcntl() function. But apparently it doesn’t work, fcntl function call return with errorno:22 (/* Invalid argument*/).
Anyone has any idea? I guess qnx does’t support O_DSYNC flag for serial port, is that right?
Any idea how to walk around this: how to write() comm in a synchronous mode?
Attached is the code I used.
Thanks.
//*************** Code ***************************
#include
#include
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <pthread.h>
#include <fcntl.h>
#include <stdarg.h>
#include <termios.h>
#include <time.h>
#include <errno.h>
using namespace std;
int main (int argc, char **argv)
{
int serf = open("/dev/ser1", O_RDWR );
if (serf == -1)
{
cout << “Fail to open COM.” << endl;
exit(1);
}
int retval = fcntl(serf, F_SETFL, O_DSYNC );
if( retval == -1 ) {
printf( "error setting stdout flags, with errorno=%d\n", errno);
return EXIT_FAILURE;
}
ifstream iFile;
char* iFileName = "/etc/printers/epijs.cfg";
iFile.open(iFileName, ios::binary);
if(!iFile.is_open())
{
cout << "Error opening input file named: " << iFileName << endl;
exit (1);
}
int wcount;
while(!iFile.eof())
{
char buffer[132];
iFile.read(buffer, 132);
wcount=iFile.gcount();
if (write(serf, buffer, wcount) != wcount)
{
cout << "Write error!" << endl;
exit (1);
};
}
iFile.close();
close(serf);
return EXIT_SUCCESS;
}