I run a lot of "setup" scripts. I made them to speed installs of software.
Now other people are using them. Several times
in the scripts users need to edit a file or some other
activity that will change the way in which the user might expect the script to run.
S/he needs to realize this _before_ the the event starts.
Hence a snippet!


Takes one arg requried, the time to countdown.
One arg possibe, a description of what's comming.
kinda looks like this with the number changing each second:
5 seconds until event 

sub timetill($;$)
{
    my $pipe = $|;#pipe value is saved
    $| = 1;#pipe value changed to flush the buffer
    my $time = shift || return -1;#how long
    my $line = shift || " seconds until event";#what
    chomp $time;
    chomp $line;
    my $backcount = length $line;
    $backcount+=7;#this is where you might need to edit
          #to suit you. Spaces, and number display is added
          #to the total count to backup
    while($time > 0)
    {
        print " " . ' ' x (3 - length($time)) .          
                    "$time $line";
        foreach (1..$backcount){print "\b"}
        $time -= 1;
        sleep 1;
    }
    $| = $pipe;#yea maybe I don't need to replace $| 
                   #but I sleep better knowing I'd put     
                   #everyting back the way I found it.
#I tend to use it like this:
#timetill(10, 'edit /etc/inetd.conf');
#system("vi /etc/inetd.conf");
}

[download]

Replies are listed 'Best First'.
Re: Time until event
by blokhead (Monsignor) on Sep 19, 2002 at 15:44 UTC
    You may want to consider changing the following. It's shorter, and it's probably how I would have written the loop. I realize life is not one big Perl-golf challenge, but in this case I prefer the shorter version. 
    while ($time > 0) {
  print " " . ' ' x (3 - length($time)) . "$time $line";
  foreach (1..$backcount){print "\b"}
  $time -= 1;
  sleep 1;
}

    [download]
    to 
    while ($time--) {
  printf(" %3s %s", $time, $line);

  print "\b" for (1..$backcount);
  # or this could even be written as:
  # print "\b" x $backcount;

  sleep 1;
}

    [download]
    No need to do the formatting of the time yourself, sprintf or printf can do it for you. The %3s part means format the string $time, right-justified within a column of 3 characters (space-padded if necessary). You could also do %3d as part of your printf format to do the same thing with zero-padding instead. See the perldoc page for printf for more fun options.

    Having said that, I haven't actually executed your code, but I wonder if printing out backspaces isn't the most efficient way to erase the line. I don't have any other suggestions though, so I may be off base. Anyway, good job in saving/replacing $| within your sub. Returning globals to their previous values can save a lot of headaches.

    blokhead

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        "I wonder if printing out backspaces isn't the most efficient way to erase the line."

      Actually, "\r" serves that purpose, unless you are overprinting in mid-line.   But even then, simply reprinting the unchanging beginning of the line still seems simplest.
      eg, 
      printf(" %3d %s\r", $time, $line);

while(--$time) {
  sleep 1;
  printf(" %3d\r", $time);
}
print"\n";

      [download]
      See this whirligig for a similar function.

        p
[reply]
[d/l]
Re: Time until event
by Aristotle (Chancellor) on Sep 19, 2002 at 19:18 UTC
    See comments. 
    sub timetill { # don't use prototypes
   local $| = 1; # will be restored on exit scope

   my $time = shift || return; # use "undef" to signal errors in Perl
   my $line = shift || " seconds until event";

   # why chomp?

   while($time > 0) {
       my $prompt = sprintf "%3d $line", $time;
       print $prompt;
       sleep 1;
       print "\b" x length $prompt; # no need to edit the function
       $time--;
   }
}

    [download]

    Please read Are prototypes evil? and Tom Christiansen's explanation on prototypes.

    Makeshifts last the longest.

[reply]
[d/l]

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