How can I start an interactive console for Perl, similar to the irb command for Ruby or python for Python?
How can I start an interactive console for Perl, similar to the irb command for Ruby or python for Python?
You can use the perl debugger on a trivial program, like so:
perl -de1
Alternatively there's Alexis Sukrieh's Perl Console application, but I haven't used it.
Not only did Matt Trout write an article about a REPL, he actually wrote one - Devel::REPL
I've used it a bit and it works fairly well, and it's under active development.
BTW, I have no idea why someone modded down the person who mentioned using "perl -e" from the console. This isn't really a REPL, true, but it's fantastically useful, and I use it all the time.
I wrote a script I call "psh":
#! /usr/bin/perl
while (<>) {
chomp;
my $result = eval;
print "$_ = $result\n";
}
Whatever you type in, it evaluates in Perl:
> gmtime(2**30)
gmtime(2**30) = Sat Jan 10 13:37:04 2004
> $x = 'foo'
$x = 'foo' = foo
> $x =~ s/o/a/g
$x =~ s/o/a/g = 2
> $x
$x = faa
I think you're asking about a REPL (Read, Evaluate, Print, Loop) interface to perl. There are a few ways to do this:
I use the command line as a console:
$ perl -e 'print "JAPH\n"'
Then I can use my bash history to get back old commands. This does not preserve state, however.
This form is most useful when you want to test "one little thing" (like when answering Perl questions). Often, I find these commands get scraped verbatim into a shell script or makefile.
There isn't an interactive console for Perl built in like Python does. You can however use the Perl Debugger to do debugging related things. You turn it on with the -d option, but you might want to check out 'man perldebug' to learn about it.
After a bit of googling, there is a separate project that implements a Perl console which you can find at Perl Console - Perl code interactive evaluator with completion.
Hope this helps!
You can always just drop into the built-in debugger and run commands from there.
perl -d -e 1
I always did:
rlwrap perl -wlne'eval;print$@if$@'
With 5.10, I've switched to:
rlwrap perl -wnE'say eval()//$@'
(rlwrap is optional)
You could look into psh here: http://gnp.github.io/psh/
It's a full on shell (you can use it in replacement of bash for example), but uses perl syntax.. so you can create methods on the fly etc.
Perl doesn't have a console but the debugger can be used as one. At a command prompt, type perl -de 1. (The value "1" doesn't matter, it's just a valid statement that does nothing.)
There are also a couple of options for a Perl shell:
Archived "perlfaq3" page which contain question "Is there Perl Shell?"
For more information read perlfaq3 (current version).
You can do it online (like many things in life) here:
You can use org-babel in emacs; Open an org-mode file, i.e., tmp.org, and then you can do:
#+begin_src perl :results output
@a = (1,5,9);
print ((join ", ", @a) . "\n");
$b = scalar @a;
print "$#a, $b\n";
print "$#a, " . @a . "\n";
print join ", ", 1..$#a; print "\n";
print join ", ", @a[0..$#a]
#+end_src
Pressing CTRL-c CTRL-c evals the block:
#+RESULTS:
#+begin_example
1, 5, 9
2, 3
2, 3
1, 2
1, 5, 9
#+end_example
I am not sure what emacs config this needs to work, but I think you can just install https://github.com/hlissner/doom-emacs and enable its perl and org-mode modules.