Filehandles

[Guenther Sohler]

Hallo,

I am writing a small parser in perl, which should also be able to
include files.
if a include statement happens,
the prg shall put the current FH onto the stack and open a new file with
the same FH.

How can I do this as filehandles are special in perl ?

 

[Tassilo v. Parseval]

Also sprach Guenther Sohler:

I am writing a small parser in perl, which should also be able to
include files.
if a include statement happens,
the prg shall put the current FH onto the stack and open a new file with
the same FH.

How can I do this as filehandles are special in perl ?

Just pretend that they aren't special. Filehandles no longer need to be
barewords:

open my $fh, "<", $file or die "$file: $!";
push @stack, $fh;

...

# and then later
my $element = pop @stack;
if (ref($element) eq 'GLOB') { # is it a filehandle?
while (<$element>) { # then: read file
...
}
}

Note that your terminology is a bit sloppy: If it's a filehandle then
the underlying file has already been opened and you cannot really "open
a new file with the same FH".

Tassilo

 

[Anno Siegel]

Hallo,

I am writing a small parser in perl, which should also be able to
include files.
if a include statement happens,
the prg shall put the current FH onto the stack and open a new file with
the same FH.

How can I do this as filehandles are special in perl ?

You use what is known as a lexical filehandle:

open my $fh, $file;

These are (slightly simplified) lexical variables that contain a reference
to an anonymous filehandle. The filehandle itself is still global.

Also search CPAN for the keyword "include". What comes up looks like
your problem has been dealt with before.

Anno

 

[Tad McClellan]

put the current FH onto the stack

How can I do this as filehandles are special in perl ?

perldoc -q filehandle


How can I make a filehandle local to a subroutine? How do I
pass filehandles between subroutines? How do I make an array
of filehandles?

 

[Brian McCauley]

Note that your terminology is a bit sloppy: If it's a filehandle then
the underlying file has already been opened and you cannot really "open
a new file with the same FH".

Er, no. Perl filehandles (aka "IO thingys") can exist in a closed state
and a new file can be associated with an existinh file handle with open().

 

[Brian McCauley]

Er, no.

Ignore that.

I now realise you were drawing a destinction between "file handle" and
"IO handle". When a filehandle is closed it just becomes a closed IO
handle.