Re: Another Q about piping Perl

The idiom to execute perl statements on and print the result of each line of a file is
perl -pe 'perl_statements' < file
or
some_command | perl -pe 'perl_statements'

each line is stored in $_ on which perl_statements act.

Here you want to print all the files in the $HOME/Mail directory. An all perl solution is:
map{ -f $_ and print "$_ " } <$ENV{HOME}/MAIL/*>

Some people consider using map on empty context is bad form. I don't. They would propose instead: for(<$ENV{HOME}/MAIL/*>) { -f $_ and print "$_ " }
or
-f $_ and print "$_ " for <$ENV{HOME}/MAIL/*>

TMTOWTDI

-- stefp

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(Ovid) Re(2): Another Q about piping Perl by Ovid (Cardinal) on Oct 12, 2001 at 03:39 UTC
stefp wrote: Some people consider using map on empty context is bad form. I don't. I think it depends on the context. If you're doing a short one-liner like that, it's not a big deal. In fact, if you're just writing a small "throw away" script that only gets used once or twice and you don't care about performance or memory, then it's not a big deal IMHO. However, if you're writing large applications, it pays to be rigorous. Creating a bunch of only to throw away the return value is a waste of resources and a for loop is preferable. Doing what you did to print all the files in the `$HOME/MAIL/` directory: `# print all files in the directory (an overblown and limited 'ls' +or 'dir' perl -e '-f $_ and print "$_ " for glob(shift)' ./` [download] Side note: since I tested that on a Windows box and it doesn't like single quotes on the command line and I hate using `\"` all the time to embed quotes, I wrote this: `perl -e "-f $_ and print $_.$,.$/ for glob(shift)" ./` [download] No wonder people say Perl has too much punctuation :) Cheers, Ovid Update: Hmm... seems I wasn't paying attention to blakem's post. Vote for paco! Join the Perlmonks Setiathome Group or just click on the the link and check out our stats.	[reply] [d/l] [select]
Re: Re: Another Q about piping Perl by blakem (Monsignor) on Oct 12, 2001 at 03:25 UTC
I like map as much as the next guy (see the "extended" Location field on my homenode) but why not write the above map as: `-f $_ && print "$_ " for <$ENV{HOME}/MAIL/*>` [download] -Blake	[reply] [d/l]