Manipulates a file descriptor.

This function is compatible with the following targets:

ANSI

BeOS

EMB/RTOS

Mac OS

Palm OS

Win32

#include <fcntl.h>

int fcntl(int fildes, int cmd, ...);

Parameters for this facility are:

fildes	int	The file descriptor
cmd	int	A command to the file system
...		A variable argument list

This function performs the command specified in cmd on the file descriptor fildes.

In the Metrowerks ANSI library, fcntl() can perform only one command, F_DUPFD. This command returns a duplicate file descriptor for the file that fildes refers to. You must include a third argument in the function call. The new file descriptor is the lowest available file descriptor that is greater than or equal to the third argument.

Mode	Description
F_DUPFD	Return a duplicate file descriptor.

If it is successful, fcntl() returns a file descriptor. If it encounters an error, fcntl() returns -1.

"fileno"

"open"

"fdopen".

#include <unix.h>

int main(void)
{
	int fd1, fd2;

	fd1 = open("mytest", O_WRONLY | O_CREAT);

	write(fd1, "Hello world!\n", 13);
		/* Write to the original file descriptor.                      */
	
	fd2 = fcntl(fd1, F_DUPFD, 0);
		/* Create a duplicate file descriptor.                            */

	write(fd2, "How are you doing?\n", 19);
		/* Write to the duplicate file descriptor.                    */

	close(fd2);	

	return 0;
}
/*ReslutAfter you run this program, 
the file mytest contains the following:
Hello world!
How are you doing?
*/





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Last updated: August 16, 2000