openfd()

Open for private access a file associated with a given descriptor

Synopsis:

#include <unistd.h>

int openfd( int fd,
            int oflag );

Arguments:

fd

A file descriptor associated with the file that you want to open.

oflag

How you want to open the file; a combination of the following bits:

O_RDONLY — permit the file to be only read.
O_WRONLY — permit the file to be only written.
O_RDWR — permit the file to be both read and written.
O_APPEND — cause each record that's written to be written at the end of the file.
O_TRUNC — truncate the file to contain no data.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

The openfd() function opens the file associated with the file descriptor, fd. This is similar to dup(), except the new fd has private access modes and offset. The access mode, oflag, must be equal to or more restrictive than the access mode of the source fd.

Returns:

A file descriptor, or -1 if an error occurred (errno is set).

Errors:

EBADF: Invalid file descriptor fd.
EACCES: The access mode specified by oflag isn't equal to or more restrictive than the access mode of the source fd.
EBUSY: Sharing mode (sflag) was denied due to a conflicting open (see sopenfd()).

Examples:

#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>

int main ( void )
{
    int fd, fd2, oflag;

    fd = open ("/etc/passwd", O_RDONLY);
    fd2 = openfd ( fd, O_RDONLY );
    return EXIT_SUCCESS;
}

Classification:

QNX Neutrino

Safety:
Cancellation point	Yes
Interrupt handler	No
Signal handler	Yes
Thread	Yes