RE: Why is this a problem?
Title: Message
See
answers:
my %fh = ( aa = 1, bb =2, cc = 3) ;
# note that each instance of $fh{$fhkey} has a different valueforeach my
$fhkey ( keys %fh){ open ( $fh{$fhkey}, "$fhkey"
) ;## so, you open 3 file handles,
one named "1", one named "2", and one named "3"
}
non-working
code
my %fh = ( aa = 1, bb =1, cc = 1)
; # note - only change, each $fh{} has value of
1foreach my $fhkey ( keys %fh){ open (
$fh{$fhkey}, "$fhkey" ) ; }##
Mmmm, because you only
open one uniquely named file handle? Specifically, named
"1"?
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Re: Why is this a problem?
Hugh Loebner wrote:
Hello perl gurus,
I spent almost a whole day solving this problem. However, I wonder why
it's a problem.
#
# The following program (which is what I started out with) will NOT work
properly: Each element of %fh has a value of 1
# Why doesn't this work properly? - all statements write to one file
#
my%fh = ( aa = 1, bb =1, cc = 1) ;# note - only change, each
$fh{} has value of 1
The proper way to do this would be to use Symbol:
use Symbol;
my %fh = (aa = gensym, bb = gensym, cc = gensym);
Barring that, you could use a ref to typeglob :
my %fh = (aa = \*1, bb = \*2, cc = \*3);
If you use 1,1,1 instead of 1,2,3 - then they'll all be pointing to the
same symbolic reference and essentially the same file.
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey ) ;
}
foreach my $fhkey ( keys %fh ){
print { $fh{$fhkey} } xxx $fhkey xxx \n ;# note file handle
$fh{$fhkey} has to be in a block
} ;
foreach my $fhkey ( keys %fh ){
close $fh{$fhkey} ;
}
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Re: Why is this a problem?
At 09:20 AM 7/1/05 -0400, [EMAIL PROTECTED] wrote:
# this works fine, produces three files, aa , bb, cc with contents 'xxx aa
xxx' etc
my %fh = ( aa = 1, bb =2, cc = 3) ; # note that each instance of
$fh{$fhkey} has a different value
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey ) ;
}
In this case, ur successively opening three file handles, with the values,
1, 2, and 3. If you want the file handle to be the name of the key, it
should be $fhkey not $fh{$fhkey}.
# The following program (which is what I started out with) will NOT work
properly: Each element of %fh has a value of 1
# Why doesn't this work properly? - all statements write to one file
my %fh = ( aa = 1, bb =1, cc = 1) ; # note - only change, each $fh{} has
value of 1
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey ) ;
}
Here ur opening the same file handle, 1, three times.
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0100
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RE: Why is this a problem?
Because the first parameter passed to open
is the file handle. In the first case, there are 3 file handles: 1,2,3. In
the second case, the same file handle is used for each file, always 1.
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Hugh Loebner
Sent: Friday, July 01, 2005 9:21
AM
To: Perl-Win32-Users Mailing List;
activeperl@listserv.ActiveState.com
Subject: Why is this a problem?
Hello perl gurus,
I spent almost a whole day solving this problem. However, I wonder why
it's a problem.
#
use strict;
no strict refs ;
# this works fine, produces three files, aa , bb, cc with contents 'xxx aa xxx'
etc
my %fh = ( aa = 1, bb =2, cc = 3) ; # note
that each instance of $fh{$fhkey} has a different value
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey )
;
}
foreach my $fhkey ( keys %fh ){
print { $fh{$fhkey} } xxx $fhkey xxx \n
; # note file handle $fh{$fhkey} has to be in a block
} ;
foreach my $fhkey ( keys %fh ){
close $fh{$fhkey} ;
}
#
# The following program (which is what I started out with) will NOT work
properly: Each element of %fh has a value of 1
# Why doesn't this work properly? - all statements write to one file
#
my %fh = ( aa = 1, bb =1, cc = 1)
; # note - only change, each $fh{} has value of 1
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey )
;
}
foreach my $fhkey ( keys %fh ){
print { $fh{$fhkey} } xxx $fhkey xxx \n
; # note file handle $fh{$fhkey} has to be in a
block
} ;
foreach my $fhkey ( keys %fh ){
close $fh{$fhkey} ;
}
#
Hugh Loebner
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RE: Why is this a problem?
Hugh Loebner wrote:
foreach my $fhkey ( keys %fh){
open ( $fh{$fhkey}, $fhkey ) ;
}
Nobody mentioned this yet: Since you want your filehandles to be unique, why
not use the key of the hash instead of the value? In other words, change the
above to:
foreach my $fhkey ( keys %fh){
open ( $fhkey, $fhkey ) ;
}
- Mark.
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