Re: [Caml-list] Re: Unix.getlogin () fails when stdin is redirected

[Yaron Minsky <yminsky@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 3471 bytes --]

Is there a concrete difference in behavior you're concerned about?

y

On Tue, Mar 20, 2012 at 2:48 PM, Till Varoquaux <till@pps.jussieu.fr> wrote:

> getpwuid(getuid()) is not a synonym for get_login (refer to the
> discussion in the POSIX standard[^1]). You should not shadow posix
> functions by functions with different semantics in the Unix modules;
> providing your own abstraction over the OS is a commendable goal but
> you should do so without silently bypassing core functions.
>
> Till
> [1]:http://pubs.opengroup.org/onlinepubs/007904975/functions/getlogin.html
>
>
> On Tue, Mar 20, 2012 at 2:28 PM, David House <dhouse@janestreet.com>
> wrote:
> > Note that Jane Street's core library [1] does not use getlogin(3) in its
> > replacement Unix module, for exactly this reason:
> >
> > (* The standard getlogin function goes through utmp which is unreliable,
> >  see the BUGS section of getlogin(3) *)
> > let getlogin_orig = Unix.getlogin
> > let getlogin () = (Unix.getpwuid (getuid ())).Unix.pw_name
> >
> > [1]: https://bitbucket.org/yminsky/ocaml-core/wiki/Home
> >
> > I just tested your specific example, and it worked fine.
> >
> >
> > On Tue 20 Mar 2012 06:07:59 PM GMT, Ricardo Catalinas Jiménez wrote:
> >>
> >> On Tue, Mar 20, 2012 at 06:51:13PM +0100, Ricardo Catalinas Jiménez
> wrote:
> >>>
> >>> I found out the next issue in this simple code:
> >>>
> >>> let () =
> >>>     print_endline "Hello";
> >>>     print_endline (Unix.getlogin ())
> >>>
> >>> Running in the normal case, with `./a.out' gives:
> >>>
> >>> Hello
> >>> ricardo
> >>>
> >>> But running like `./a.out</dev/null' makes Unix.getlogin fail:
> >>>
> >>> Hello
> >>> Fatal error: exception Unix.Unix_error(20, "getlogin", "")
> >>>
> >>> A simple strace reveals the problem:
> >>>
> >>>    open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
> >>>    fstat(3, {st_mode=S_IFREG|0644, st_size=509, ...}) = 0
> >>>    mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS,
> -1,
> >>> 0) = 0x7fb125554000
> >>>    read(3, "root:x:0:0:root:/root:/bin/bash\n"..., 4096) = 509
> >>>    read(3, "", 4096)                       = 0
> >>>    close(3)                                = 0
> >>>    munmap(0x7fb125554000, 4096)            = 0
> >>> ->  ioctl(0, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or
> >>> TCGETS, 0x7fff12682c98) = -1 ENOTTY (Inappropriate ioctl for device)
> >>>    write(2, "Fatal error: exception Unix.Unix"..., 59) = 59
> >>>    exit_group(2)                           = ?
> >>
> >>
> >>
> >> Someone knew the answer, man 3 getlogin reads:
> >>
> >>        Note that glibc does not follow the POSIX specification and uses
> >>        stdin instead of /dev/tty.  A bug.  (Other recent systems, like
> >>        SunOS 5.8 and HP-UX 11.11 and FreeBSD 4.8 all return the login
> >>        name also when stdin is redirected.)
> >>
> >>
> >> Regards
> >
> >
> >
> >
> > --
> > Caml-list mailing list.  Subscription management and archives:
> > https://sympa-roc.inria.fr/wws/info/caml-list
> > Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> > Bug reports: http://caml.inria.fr/bin/caml-bugs
> >
>
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa-roc.inria.fr/wws/info/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>
>

[-- Attachment #2: Type: text/html, Size: 5139 bytes --]