Perl hash question: How do I print the elements stored in a hash in Perl?
Answer: There are at least two ways to print the elements of a Perl hash, including one way that I think is easy to remember, and another way that is recommended if you have a very large hash.
Perl hash printing with a foreach loop
The easier way for me to remember is with a Perl foreach loop. In the following sample code I'll first create a Perl hash, and then I'll print out each key and value stored in the hash:
#!/usr/bin/perl
# create our perl hash
$prices{"pizza"} = 12.00;
$prices{"coke"} = 1.25;
$prices{"sandwich"} = 3.00;
#--------------------------------------------------
# option 1:
# print the hash key and value using a foreach loop
#--------------------------------------------------
foreach $key (keys %prices)
{
print "$key costs $prices{$key}\n";
}
As mentioned, I think this Perl foreach syntax is easier to remember, and I use it very often.
The Perl while/each approach
The second approach is to the use Perl's each operator and a Perl while loop. Here's a sample Perl script that demonstrates this:
#!/usr/bin/perl
# create our perl hash
$prices{"pizza"} = 12.00;
$prices{"coke"} = 1.25;
$prices{"sandwich"} = 3.00;
#---------------------------------------------
# option 2:
# traverse the hash using the "each" function.
# better for when the hash may be very large.
#---------------------------------------------
while (($key, $value) = each (%prices))
{
print "$key costs $prices{$key}\n";
}
As mentioned, I can't seem to remember this Perl while/each syntax as easily as I can remember the Perl foreach syntax, but this approach is supposed to perform better than the other approach. I haven't tested this performance myself, so if you think you have a very large hash in Perl script, and performance is slow, you can try this as an optimization approach.
Related Perl hash tutorials
I hope you found this short Perl hash tutorial helpful. We have many more Perl hash tutorials on this site, including the following:
Getting started Perl hash tutorials:
- Perl hash introduction/tutorial
- Perl foreach and while: how to loop over the elements in a Perl hash
- Perl hash add - How to add an element to a Perl hash
- How to print each element in a Perl hash
More advanced Perl hash tutorials:
The hash in Perl - hash sorting tutorials:
- Perl hash sorting - Sort a Perl hash by the hash key
- Perl hash sorting - Sort a Perl hash by the hash value
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