Re: Add login_tty

[Felix Janda <felix.janda@posteo.de>]

Szabolcs Nagy wrote:
> * Felix Janda <felix.janda@posteo.de> [2014-08-26 18:56:28 +0200]:
> > --- /dev/null
> > +++ b/src/misc/login_tty.c
> > @@ -0,0 +1,14 @@
> > +#include <utmp.h>
> > +#include <sys/ioctl.h>
> > +#include <unistd.h>
> > +
> > +int login_tty(int fd)
> > +{
> > +	setsid();
> > +	if (ioctl(fd, TIOCSCTTY, (char *)0)) return -1;
> > +	dup2(fd, 0);
> > +	dup2(fd, 1);
> > +	dup2(fd, 2);
> > +	if (fd>2) close(fd);
> > +	return 0;
> > +}
> 
> i recently came across this:
> http://lxr.free-electrons.com/source/fs/file.c#L751
> 
> so dup2 may spuriously fail with EBUSY on linux
> 
> the current forkpty does not check dup2 either, but i
> wonder if it should be
> 
>  while(dup2(fd,0)==-1 && errno==EBUSY);
> 
> instead

The other possibility for dup2 to fail seems to be EINTR.
(We already know that fd can't be invalid.)
Should this also be checked?

Felix