How to select a file handle depending on user options

gg48gg has asked for the wisdom of the Perl Monks concerning the following question:

Hi all, I am trying to use a file if a file is given by the user, otherwise use STDIN. It is not working, and I am not sure of the best way to do this. I could use some advice. I suspect I need some honing of my understanding of using variables with filehandles.

if ($FILE) {
 open(FILE,"<",$FILE) || fatal_error("Unable to open file $FILE");
 $HANDLE='FILE'
}
else {
 $HANDLE='STDIN';
}

######################################################################
+##########
#MAIN
######################################################################
+##########
while (defined(my $line = <$HANDLE>)) {
 print "$line";
}
[download]

Comment on How to select a file handle depending on user options Download Code

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Re: How to select a file handle depending on user options by choroba (Cardinal) on Jun 18, 2012 at 21:53 UTC
You assign strings 'FILE' and 'STDIN' instead of handles. Use `$HANDLE = FILE; ... $HANDLE = STDIN;` [download] Update: or use `\*FILE` for a reference. See Typeglobs and Filehandles.	[reply] [d/l] [select]
Re: How to select a file handle depending on user options by morgon (Priest) on Jun 18, 2012 at 23:14 UTC
You handle STDIN wrong (you need a filehandle or a typeglob - not a string) and it is usually better to use lexical variables for filehandles. One way of doing it would be: `use IO::File; my $handle = $FILE ? do { IO::File->new($FILE) or fatal_error(".."); } : *STDIN; # later you can use <$handle>` [download]	[reply] [d/l]
Re^2: How to select a file handle depending on user options by gg48gg (Sexton) on Jun 20, 2012 at 13:32 UTC
so IO::File->new returns the file handle? I have never seen do used in a ternary like that. Interesting. Thank you.	[reply]
Re: How to select a file handle depending on user options by linuxkid (Sexton) on Jun 19, 2012 at 20:29 UTC
use the `<>` operator in while, and it will set `$_` --linuxkid imrunningoutofideas.co.cc	[reply] [d/l] [select]

--linuxkid