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

Hello monks, thank you for your time. I am wondering about the proper syntax for inputing files at the command line and sending them to separate hashes. perl -walne '$h{$F[0]}.="$F[1]";END{print "$_:\t" . $h{$_} for sort keys%h}' file1.txt.

Now lets say I want to read in a second file as a second hash in the same execution... what is the syntax to tell perl that file1 and file2 should go to separate hashes?

perl -walne '$h{$F[0]}.="$F[1]" Now here is where I want to read in file2.txt into %h2 ;END{$_=......... ' file1.txt file2.txt

Any ideas on how to do this? Thanks a ton!!

UPDATE

how about something simpler... file one is a list, and I want to print out every line in file 2 that matches the current element in the list. In a script you would do this by making a nested foreach loop or you could do it by making a hash and then checking the hash.. How would one do this at command line (specifically dealing with 2 files ) ? Something like this where the file 2 lines only are piped in to the matching part:

 perl -F: -walne'$h{$F[0]}.="$F[1] "; END{#Line from file2 here#=~/$h{$_}/&&print"$h{$_}"for keys%h}' file1.txt file2.txt

Replies are listed 'Best First'.
Re: How to supply to input files at command line
by jwkrahn (Abbot) on Apr 17, 2012 at 19:54 UTC

    $ARGV is the name of the current file being processed so you could do something like this: 

    perl -walne '$h{$ARGV}{$F[0]}.="$F[1]";END{ print ...}' file1.txt file
+2.txt

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Re: How to supply to input files at command line
by brx (Pilgrim) on Apr 17, 2012 at 17:53 UTC
    Take a look to eof
    In a while (<>) loop, eof or eof(ARGV) can be used to detect the end of each file, whereas eof() will detect the end of the very last file only.

    Update: try this not tested version
     perl -walne '$;="\t";$i||=0;$h{$i,$F[0]}.="$F[1]" } continue { $i++ if eof; END{print "$_:\t" . $h{$_} for sort keys %h}' file1.txt file2.txt

    Seems OK

    $ perl -MO=Deparse -walne '$;="\t";$i||=0;$h{$i,$F[0]}.="$F[1]" } cont
+inue { $i++ if eof; END{print "$_:\t" . $h{$_} for sort keys %h}' fil
+e1.txt file2.txt
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined($_ = <ARGV>)) {
    chomp $_;
    our(@F) = split(' ', $_, 0);
    $; = "\t";
    $i ||= 0;
    $h{join $;, $i, $F[0]} .= "$F[1]";
}
continue {
    ++$i if eof;
}
sub END {
    print "${_}:\t" . $h{$_} foreach (sort keys %h);
}
-e syntax OK

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