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Closure to change output

/ Published in: Perl
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  1. ## Define three types printers: 1.Pipe to less, 2.Output to a file 3.Just print
  2. ##
  3. ##
  4.  
  5.    sub getLessPrinter {
  6.      my $pout= IO::File->new( "| less" ) or croak "Failed to create less pipe\n";
  7.  
  8.      return sub { my $line= shift;
  9.                   return $pout->print( $line ) if defined $line;
  10.                   $pout->close(); # undef to close
  11.             } # closure     
  12.    } # getLessPrinter
  13.  
  14.    sub getFilePrinter {
  15.      my $file= shift;
  16.      my $fout= IO::File->new( "> $file" ) or croak "Failed to create file: $file: $!\n";
  17.  
  18.      return sub { my $line= shift;
  19.                   return $fout->print( $line ) if defined $line;
  20.                   $fout->close(); # undef to close
  21.             } # closure     
  22.    } # getFilePrinter
  23.  
  24.   sub getNoLessPrinter {
  25.  
  26.      return sub { my $line= shift;
  27.                   print $line if defined $line;
  28.             } # closure     
  29.   } # getNoLessPrinter
  30.  
  31.  
  32.   ## Then select one of the printer
  33.   ##
  34.   ## my $printer= getFilePrinter( "output.txt");
  35.   ##    or
  36.   ## my $printer= getNoLessPrinter();
  37.   ##    or
  38.   my $printer= getLessPrinter();
  39.  
  40.   $printer->( "Something to print.\n");
  41.   $printer->( undef ); # to close the stream if needed.

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