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

been really struggling here.... probably a dumb approach

so I have 3 files, file1,file2,file3 generated by filehandles over ssh. File are written on local machine and contain CSV data coming from 6 nodes (need to stay like this). My script works but I am trying to optimize with a foreach loop on each of the files rather than hard coded for each.

so I have this array: 
@FILES = ( 1, 2, 3 );
foreach $FILE (@FILES) {

   # Open filehandle tailing file written by ssh<br><br>
   open ( ${fh.$FILE}, "tail -f file$FILE |") || die "can't open file$
+FILE";
   while ( ${line.$FILE} = ${fh.$FILE} ) {
      
      # Here I do my split on the CSV line and assign to arrays (keepi
+ng the 
      # $FILE value as a suffix to the array name)<br><br>

      @{fields.$FILE} = split(/,/,${line.$FILE});
      push @{AAA.$FILE}, ${fields.$FILE[0]};

      # .....

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The issue I have is that ${line.$FILE} does not seem to be filled by the filehandle, I get the mem address (GLOB(0x563b358e1060) for example).

any help greatly appreciated!

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Re: Filehandle/array naming
by bliako (Abbot) on Nov 20, 2020 at 11:30 UTC

    try enclosing the filehandle in <>,

    Edit: The above won't work because the inside to the diamond operator must be a simple scalar variable and ${fh.$FILE} is not (why?). See choroba's answer

     while ( ${line.$FILE} = <${fh.$FILE}> ) {

    I must note that yours is definetely uncommon coding style! I usually use arrays rather than creating unqiue variables, one for each array item, whose name contains the array index. If I deciphered your code correctly that is.

    EDIT: I forgot the tail -f, perhaps you want to replace that with a Perl module: File::Tail

    bw, bliako

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      This won't work, unfotunately. See perlop:

      > If what's within the angle brackets is neither a filehandle nor a simple scalar variable containing a filehandle name, typeglob, or typeglob reference, it is interpreted as a filename pattern to be globbed, and either a list of filenames or the next filename in the list is returned, depending on context. This distinction is determined on syntactic grounds alone. That means <$x> is always a readline() from an indirect handle, but <$hash{key}> is always a glob(). That's because $x is a simple scalar variable, but $hash{key} is not--it's a hash element. Even <$x > (note the extra space) is treated as glob("$x "), not readline($x).

      So, use readline, not the diamond.

      map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
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        A clarification is needed: if $x is a "simple scalar variable", then what is ${fh.$FILE}?

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        Thx a Million Choroba, that solved it!!!!
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      Thx Bliako, I did have the <> in my code, not sure why it did not make it in my post. But that did not work either, readline was the golden ticket!
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Re: Filehandle/array naming
by Anonymous Monk on Nov 20, 2020 at 13:24 UTC
    open ( ${fh.$FILE}, "tail -f file$FILE |") || die "can't open file$FILE";
    You are probably much better off storing those filehandles in a data structure, say, a hash, instead of creating a set of related variables with programmatically obtained names. How can I use a variable as a variable name? explains it better than I can do at the moment.
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