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

Actually this is sort of related to a question I saw earlier about reporting the status of something being done. One thing I always sort of wanted to do is make a spinner. By spinner I mean a simple section of text which changes from | to / to - to \ . While I was booting Free BSD and watching one, I thought about how something like this could enhance my programs, and at least show that they're still working (and not hanging) - this became especially apperent today when I wrote an encryption program that takes a LONG time. If I could somehow show something happening around every 100th iteration of the main loop, I could at least show that it is doing something. But here's the catch, I want it to work in both Unix AND Windows. I know Term has the functionality I need, but it doesn't support Windows. About the only thing I could come up with was the following (this is just example code):

#!/usr/bin/perl

my $spinner;
my @spinState = ("-", "\\", "|", "/");

foreach(1..25) {
  print "Working: " . $spinState[$spinner] . "\n";
  print "    \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
  sleep(1);

}

[download]

And as you can see that's basically a pile of slop and not any real sort of solution. Actually just being able to overwrite the last character written to the screen is all I need. Any Ideas?

Replies are listed 'Best First'.
Re: making a spinner
by blakem (Monsignor) on Sep 20, 2001 at 22:40 UTC
    This seems to work on my unix VT100 terminal. It involves unbuffering the output, and printing the '\b' or backspace char. 
    #!/usr/bin/perl -wT
use strict;

$| = 1; # unbuffer output

my $spinner;
my @spinState = ("-", "\\", "|", "/");

print "Working: ";
foreach(1..25) {
  print "$spinState[$_%@spinState]";
  sleep 1;
  print "\b";  # backspace
}

    [download]

    -Blake

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[d/l]
Re: making a spinner
by shotgunefx (Parson) on Sep 20, 2001 at 22:29 UTC
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Re: making a spinner
by phubuh (Beadle) on Sep 20, 2001 at 22:54 UTC
    "\b" is for backspace, so you could do this:
    $|++;
for (my $x = 0; $x <= 25; ++$x){
  foreach (("-", "\\", "|", "/")){
    print $_; sleep 1; print "\b";
  }
}

    [download]
[reply]
[d/l]
Re: making a spinner
by archen (Pilgrim) on Sep 20, 2001 at 23:17 UTC
    yeah, \b seems to work (okay, I feel stupid now). I could have sworn there was something about it not working in an MSDOS prompt. Perhaps I confused myself recalling not being able to check input as it happens in DOS.

    Thanks!

    Here's what the revised code looks like:

    ...

print "Working: " . $spinState[$spinner];
while(read(INFILE, $buffer, 1024)) {
   print CRYPTFILE $cipher->crypt($buffer);
   &status() if(($wrap = ($wrap + 1) % 50) && not $silent);
}
print CRYPTFILE $cipher->finish;     #-- flush remaining crap in buffe
+r
...

sub status()
{
   $spinner = ($spinner + 1) % 4;
   print "\b$spinState[$spinner]";
}

    [download]
[reply]
[d/l]
      there's a variety of ascii/ escape codes that you can also use, if you're so inclined.
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Re: making a spinner
by perlisfun (Sexton) on Sep 21, 2001 at 01:05 UTC
    PerlIsFun

    Long time ago, i wrote something to transfer database table from Informix to Oracle, i used a spinner. It may help you. 

     sub transfer_Data {
  my $stn = shift;
  my $dtn = shift;
  $| = 1;
  my @spinner = ('|','/','-','\\');
  my $ifmx_stmt = "select count(*) from $stn" ;
  my $sth_ifmx = $db_ifmx->prepare($ifmx_stmt);
  $sth_ifmx->execute;
  my $count = $sth_ifmx->fetchrow();
  print "Total record number: $count \n\n";

  $ifmx_stmt = "select * from $stn" ;
  $sth_ifmx = $db_ifmx->prepare($ifmx_stmt);
  $sth_ifmx->execute;
  my $rn = 1;
  while ( my @row = $sth_ifmx->fetchrow_array ) {
    my $ds = '';
    for ( my $i = 0; $i <@row; $i++ ) {
      my $nd = trim($row[$i]);
      $nd =~ s/'/''/g;
      my $check = match_DateList($i);
      if ( $check ) {
        $ds .= "to_date('$nd', 'MM/DD/YYYY'),";
      } else {
        $ds .= "'$nd',";
      }
    }
    $ds =~ s/,$/)/;
    $ds =~ s/^/(/;
    my $orac_stmt = "insert into $dtn values " . $ds ;
    my $sth_orac = $db_orac->do($orac_stmt);
    print "Record: $rn $spinner[$rn%4]\r";
    $rn++;
  }
  $sth_ifmx->finish;
  print "\nData Transfer is complete \n\n";
  $| = 0;
}

    [download]
    It may be too much. That is what i have.

    Edit by tye

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[d/l]
Re: making a spinner
by demerphq (Chancellor) on Sep 22, 2001 at 20:44 UTC
    Cool! Two uses for Tie::Cycle* in one day! 
    use Tie::Cycle;
my $delay=5;
tie my $spinner, 'Tie::Cycle', [map {("\b$_")x$delay}qw(\ | / -)];
print $spinner while (1);

    [download]
    :-)

    Yves
    --
    You are not ready to use symrefs unless you already know why they are bad. -- tadmc (CLPM)
    * and no I didn't write it... :-)

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[d/l]
Re: making a spinner
by grummerX (Pilgrim) on Sep 21, 2001 at 17:58 UTC
    The above suggestions utilizing "\b" should work fine for your purposes, but if you need to do any terminal manipulation in Windows, you should look into Win32::Console.

    The following code basically duplicates the "\b" examples utilizing Win32::Console: 

    #!c:/perl/bin/perl -w
use strict;
use Win32::Console;
my $console = new Win32::Console(STD_OUTPUT_HANDLE);


$console->Cursor(-1,-1,-1,0);    # Turn off cursor blink

foreach (1..3) {
    foreach( ("-", "\\", "|", "/") ){
        $console->Cursor(0);    #Move cursor to beginning of line
        $console->Write($_);
        sleep 1;
    }
}

$console->Cursor(-1,-1,-1,1);    # Reset cursor blink

    [download]
    Using "\b" is obviously preferable in this case, but if you're looking into doing anything more complex Win32::Console is a good thing to keep in mind.

    --grummerX

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[d/l]
Re: making a spinner
by snafu (Chaplain) on Sep 21, 2001 at 17:45 UTC
    Between this and the other set of posts on this same topic, I think it would be a good idea to make a module for the whirleywig. I believe in the node A whirleygig for a progress indicator for scripts someone mentioned a module for this. I don't remember very well. If that wasn't a real .pm will someone make one? ;) I would but I don't have the time right now nor the knowledge of module making. BUT! It would be a great exercise for me.

    ----------
    - Jim

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