how to handle open() errors?

[fabrizio]

Opening /dev/tap0, I have an error in fact open() returns -1.

int fd = open("/dev/tap0",O_RDWR);
if (fd == -1)
{
cerr<<"error opening interface"<<endl;
}

How can I handle the error? Essentially, how can I print the error to
know the reason of it?

Thanks.

[John Harrison]

fabrizio wrote:

Opening /dev/tap0, I have an error in fact open() returns -1.

int fd = open("/dev/tap0",O_RDWR);
if (fd == -1)
{
cerr<<"error opening interface"<<endl;
}

How can I handle the error? Essentially, how can I print the error to
know the reason of it?

Thanks.

perror will print an error message to the standard error stream

int fd = open("/dev/tap0",O_RDWR);
if (fd == -1)
{
perror("error opening interface");
}

There are of coure no guarantees that the error message will be helpful.

john