Can I extract a Hash element by passing a variable to the hash?

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

I have a Hash that I want to extract data from by passing it a variable for the element name, is this possible?
For example:

system "/bin/date +%A > /tmp/day";
open (DAY, "/tmp/day") ||
die "Error opening file!";
$RUNDAY = (<DAY>);
%Backup_Day = (
   Sunday => "0",
   Monday => "1",
   Tuesday => "2",
   Wednesday => "3",
   Thursday => "4",
   Friday => "6",
);
$SLOT = $Backup_Day{$RUNDAY};
print "Slot Number is $SLOT\n";
[download]

<jdporter added code tags

Comment on Can I extract a Hash element by passing a variable to the hash? Download Code

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Re: Can I extract a Hash element by passing a variable to the hash? by ikegami (Patriarch) on Jan 27, 2006 at 20:55 UTC
Yes you can. If it doesn't work, it's probably because `$RUNDAY` probably contains `"Friday\n"` rathen than `"Friday"`. Fix: `chomp($RUNDAY = <DAY>);`. I have some suggestions for improvements. Instead of using a temporary file, you can use backticks. Uppercase variable bames usually indicate a constant. You don't need to put numbers in quotes, usually. my %BACKUP_DAY = ( Sunday => 0, Monday => 1, Tuesday => 2, Wednesday => 3, Thursday => 4, Friday => 6, ); chomp(my $runday = `/bin/date +%A`); my $slot = $BACKUP_DAY{$runday}; print "Slot Number is $slot\n"; [download] By the way, you're missing Saturday. I don't know if that's intentional. For future reference, place `<c>` and `</c>` around any code you post to make it readable.	[reply] [d/l] [select]
Re^2: Can I extract a Hash element by passing a variable to the hash? by Anonymous Monk on Jan 27, 2006 at 21:28 UTC
Thanks, that did the trick.	[reply]
Re^3: Can I extract a Hash element by passing a variable to the hash? by ikegami (Patriarch) on Jan 27, 2006 at 21:39 UTC
As I meant to mention that in my original post, you could just use localtime. `my $slot = (localtime)[6]; # 0..6 for Sun..Sat if ($slot == 6) { $slot = undef; # undef for Sat. elsif ($slot == 5) { $slot = 6; # 6 for Fri. } print "Slot Number is $slot\n";` [download]	[reply] [d/l]
Re: Can I extract a Hash element by passing a variable to the hash? by chargrill (Parson) on Jan 27, 2006 at 20:45 UTC
chargrill hands buster_balz a set of <code></code> tags... Yes, see perldoc perldata. You might find you need to `chomp()` it first. ... and why write to a file which could fail and `die`, and not use `qx//`? (see perldoc perlop) --chargrill `$/ = q#(\w)# ; sub sig { print scalar reverse join ' ', @_ } + sig map { s$\$/\$/$\$2\$1$g && $_ } split( ' ', ",erckha rlPe erthnoa stJu +" );` [download]	[reply] [d/l] [select]
Re: Can I extract a Hash element by passing a variable to the hash? by CountZero (Bishop) on Jan 27, 2006 at 20:51 UTC
Have you tried to run your program? What was it result? CountZero "If you have four groups working on a compiler, you'll get a 4-pass compiler." - Conway's Law	[reply]