[27847] in Perl-Users-Digest
Perl-Users Digest, Issue: 9211 Volume: 10
daemon@ATHENA.MIT.EDU (Perl-Users Digest)
Sat Apr 29 11:05:52 2006
Date: Sat, 29 Apr 2006 08:05:04 -0700 (PDT)
From: Perl-Users Digest <Perl-Users-Request@ruby.OCE.ORST.EDU>
To: Perl-Users@ruby.OCE.ORST.EDU (Perl-Users Digest)
Perl-Users Digest Sat, 29 Apr 2006 Volume: 10 Number: 9211
Today's topics:
Re: Detecting filehandles <someone@example.com>
Re: Detecting filehandles <matthew.garrish@sympatico.ca>
Re: Detecting filehandles <bik.mido@tiscalinet.it>
Re: How to display image from RAM with some text around <bik.mido@tiscalinet.it>
Module for a curses/Turbovision style interface <amajorel@teezer.fr>
Digest Administrivia (Last modified: 6 Apr 01) (Perl-Users-Digest Admin)
----------------------------------------------------------------------
Date: Sat, 29 Apr 2006 12:05:16 GMT
From: "John W. Krahn" <someone@example.com>
Subject: Re: Detecting filehandles
Message-Id: <0EI4g.704$zn1.341@edtnps90>
Subotai wrote:
> Is there a way to detect if an argument you are passed in a subroutine is a
> filehandle? For instance:
>
> open(FILE, '/file');
> foo(\*FILE);
> foo($someotherarg);
>
> sub foo {
> $arg = shift;
> #### do some check on $arg to see if it is a filehandle or a normal scalar
> }
Use fileno() for that, if it is defined then it is a valid filehandle.
> Also if you have an open filehandle, is there a way to see what file it is
> referencing? For instance if you open the file "/foo", is there anyway to
> get "/foo" from the filehandle? I know with the fileno() call you can get
> the file descriptor, is there anyway you could use that to lookup that
> information? I don't think there is but I want to be 100% sure.
There is if you have a /proc file system that supports it:
$ perl -le'
open my $fh, q[test.txt] or die $!;
my $fn = fileno $fh;
print readlink "/proc/self/fd/$fn";
'
/home/john/test/test.txt
Or use the PID:
$ perl -le'
open my $fh, q[test.txt] or die $!;
my $fn = fileno $fh;
print readlink "/proc/$$/fd/$fn";
'
/home/john/test/test.txt
John
--
use Perl;
program
fulfillment
------------------------------
Date: Sat, 29 Apr 2006 08:04:59 -0400
From: "Matt Garrish" <matthew.garrish@sympatico.ca>
Subject: Re: Detecting filehandles
Message-Id: <KDI4g.4763$fx.438717@news20.bellglobal.com>
"Kevin Michael Vail" <kevin@vaildc.net> wrote in message
news:kevin-A5F7F3.21594228042006@news.verizon.net...
> In article <48mdnTde3IAuLM_ZnZ2dnUVZ_s6dnZ2d@giganews.com>,
> "Subotai" <subotai@aol.com> wrote:
>
>> Is there a way to detect if an argument you are passed in a subroutine is
>> a
>> filehandle? For instance:
>>
>> open(FILE, '/file');
>> foo(\*FILE);
>> foo($someotherarg);
>>
>> sub foo {
>> $arg = shift;
>> #### do some check on $arg to see if it is a filehandle or a normal
>> scalar
>> }
>
> Look at the 'openhandle' function in Scalar::Util.
>
>> Also if you have an open filehandle, is there a way to see what file it
>> is
>> referencing? For instance if you open the file "/foo", is there anyway to
>> get "/foo" from the filehandle? I know with the fileno() call you can get
>> the file descriptor, is there anyway you could use that to lookup that
>> information? I don't think there is but I want to be 100% sure.
>
> I don't believe there is, either. It would be difficult to impossible
> to implement under Unix, because a file is one thing and its name is
> something else; in fact a file can have multiple names (directory
> entries), so how would you choose which one is "the" file?
No, but no reason you can't just use a hash to store all the information
about the file and then pass that into the subroutine:
[untested]
my %fileinfo = (filepath => '/somefile.dat');
open ($fileinfo{'filehandle'}, '<', '$fileinfo{'filepath'}) or die $!;
mySub(\%fileinfo);
sub mySub {
my ($arg1) = @_;
if (ref($arg1) eq 'HASH' and defined($arg1->{'filehandle'}) {
# have a filehandle
}
else {
# do not have a filehandle
}
}
Matt
------------------------------
Date: Sat, 29 Apr 2006 15:30:51 +0200
From: Michele Dondi <bik.mido@tiscalinet.it>
Subject: Re: Detecting filehandles
Message-Id: <t9q652h4br8d9jqan2s17hrm1qmt7lg0lq@4ax.com>
On Fri, 28 Apr 2006 18:22:07 -0600, "Subotai" <subotai@aol.com> wrote:
>Also if you have an open filehandle, is there a way to see what file it is
>referencing? For instance if you open the file "/foo", is there anyway to
Not reliably and not portably. Under Linux you can inspect /proc. Once
I did it, but that was to analize the file descriptors of *another
process*. If you really want to do it for your script itself, then
you'll need fileno(), but personally I can't see why you should want
to do so. Thus I recommend you change the logic of your code...
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{pop^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
.'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
------------------------------
Date: Sat, 29 Apr 2006 15:04:16 +0200
From: Michele Dondi <bik.mido@tiscalinet.it>
Subject: Re: How to display image from RAM with some text around
Message-Id: <unt452topfn3nn3jjrhorokr0cuspt3pde@4ax.com>
On 28 Apr 2006 18:25:16 GMT, xhoster@gmail.com wrote:
>You could use the data uri, but it doesn't work with IE.
I have also seen using JavaScript for this, but I don't have the
slightest idea how portable it could be, and one has to have JS
enabled in any case, which... may not be the case!
Michele
--
{$_=pack'B8'x25,unpack'A8'x32,$a^=sub{pop^pop}->(map substr
(($a||=join'',map--$|x$_,(unpack'w',unpack'u','G^<R<Y]*YB='
.'KYU;*EVH[.FHF2W+#"\Z*5TI/ER<Z`S(G.DZZ9OX0Z')=~/./g)x2,$_,
256),7,249);s/[^\w,]/ /g;$ \=/^J/?$/:"\r";print,redo}#JAPH,
------------------------------
Date: Sat, 29 Apr 2006 14:54:59 +0000 (UTC)
From: Andre Majorel <amajorel@teezer.fr>
Subject: Module for a curses/Turbovision style interface
Message-Id: <slrne56vi4.vc0.amajorel@atc5.vermine.org>
I'm looking into writing an interactive Perl program that runs
in a TTY. The interface will be modelled after the old NetWare
text mode utilities. I imagine that entails curses or slang and
a widget layer on top of that.
What module would you recommend for that ? Curses::UI ?
Curses::Widgets ? Something else ?
--
André Majorel <URL:http://www.teaser.fr/~amajorel/>
"The best justice that money can buy."
------------------------------
Date: 6 Apr 2001 21:33:47 GMT (Last modified)
From: Perl-Users-Request@ruby.oce.orst.edu (Perl-Users-Digest Admin)
Subject: Digest Administrivia (Last modified: 6 Apr 01)
Message-Id: <null>
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------------------------------
End of Perl-Users Digest V10 Issue 9211
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