Re: Another Q about piping Perl

[stefp]

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

[blakem]

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/*>

-Blake

[Ovid]

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)' ./*

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)" ./*

No wonder people say Perl has too much punctuation :)

Cheers,
Ovid

Update: Hmm... seems I wasn't paying attention to blakem's post.

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