Provided by: libterm-progressbar-perl_2.21-1_all 
NAME
Term::ProgressBar - provide a progress meter on a standard terminal
VERSION
Version 2.21
SYNOPSIS
use Term::ProgressBar;
my $progress = Term::ProgressBar->new ({count => 10_000});
$progress->update(5_000);
DESCRIPTION
Term::ProgressBar provides a simple progress bar on the terminal, to let the user know
that something is happening, roughly how much stuff has been done, and maybe an estimate
at how long remains.
A typical use sets up the progress bar with a number of items to do, and then calls update
to update the bar whenever an item is processed.
Often, this would involve updating the progress bar many times with no user-visible
change. To avoid unnecessary work, the update method returns a value, being the update
value at which the user will next see a change. By only calling update when the current
value exceeds the next update value, the call overhead is reduced.
Remember to call the "$progress->update($max_value)" when the job is done to get a nice
100% done bar.
A progress bar by default is simple; it just goes from left-to-right, filling the bar with
'=' characters. These are called major characters. For long-running jobs, this may be
too slow, so two additional features are available: a linear completion time estimator,
and/or a minor character: this is a character that moves from left-to-right on the
progress bar (it does not fill it as the major character does), traversing once for each
major-character added. This exponentially increases the granularity of the bar for the
same width.
EXAMPLES
A really simple use
#!/usr/bin/perl
use Term::ProgressBar 2.00;
use constant MAX => 100_000;
my $progress = Term::ProgressBar->new(MAX);
for (0..MAX) {
my $is_power = 0;
for (my $i = 0; 2**$i <= $_; $i++) {
$is_power = 1 if 2**$i == $_;
}
if ($is_power) {
$progress->update($_);
}
}
see eg/simle_use.pl
Here is a simple example. The process considers all the numbers between 0 and MAX, and
updates the progress bar whenever it finds one. Note that the progress bar update will be
very erratic. See below for a smoother example. Note also that the progress bar will
never complete; see below to solve this.
The complete text of this example is in examples/powers in the distribution set (it is not
installed as part of the module).
A smoother bar update
my $progress = Term::ProgressBar->new($max);
for (0..$max) {
my $is_power = 0;
for (my $i = 0; 2**$i <= $_; $i++) {
$is_power = 1 if 2**$i == $_;
}
$progress->update($_)
}
See eg/smooth_bar.pl
This example calls update for each value considered. This will result in a much smoother
progress update, but more program time is spent updating the bar than doing the "real"
work. See below to remedy this. This example does not call "$progress->update($max);" at
the end, since it is unnecessary, and ProgressBar will throw an exception at an attempt to
update a finished bar.
The complete text of this example is in examples/powers2 in the distribution set (it is
not installed as part of the module.
A (much) more efficient update
my $progress = Term::ProgressBar->new({name => 'Powers', count => $max, remove => 1});
$progress->minor(0);
my $next_update = 0;
for (0..$max) {
my $is_power = 0;
for (my $i = 0; 2**$i <= $_; $i++) {
$is_power = 1 if 2**$i == $_;
}
$next_update = $progress->update($_) if $_ >= $next_update;
}
$progress->update($max) if $max >= $next_update;
This example does two things to improve efficiency: firstly, it uses the value returned by
update to only call it again when needed; secondly, it switches off the use of minor
characters to update a lot less frequently ("$progress->minor(0);". The use of the return
value of update means that the call of "$progress->update($max);" at the end is required
to ensure that the bar ends on 100%, which gives the user a nice feeling.
This example also sets the name of the progress bar.
This example also demonstrates the use of the 'remove' flag, which removes the progress
bar from the terminal when done.
The complete text of this example is in examples/powers3 in the distribution set (it is
not installed as part of the module.
When the maximum number of items is sometimes unknown
Sometimes you may wish to use the progress bar when the number of items may or may not be
known. One common example is when you write a script that can take input piped from the
output of another command, and then pipe the output to yet another command. eg:
some_command --arg value | my_script.pl | some_other_command
Or ...
my_script.pl input_file output_file
This example shows how you can iterate over a file specified on the command line with the
progress bar. Since the input file may be read from STDIN, the number of lines may not be
known. Term::ProgressBar handles this by just taking '-1' as the count value and with no
further changes to the code. By calling update with the same count value, you ensure the
progress bar is removed afterwards.
my $input_file = shift;
my $output_file = shift;
my $in_fh = \*STDIN;
my $out_fh = \*STDOUT;
my $message_fh = \*STDERR;
my $num_lines = -1;
if (defined($input_file) and $input_file ne '-') {
open($in_fh, $input_file) or die "Couldn't open file, '$input_file': $!";
my $wc_output = `wc -l $input_file`;
chomp($wc_output);
$wc_output =~ /^\s*(\d+)(\D.*)?/ or die "Couldn't parse wc output: $wc_output";
$num_lines = $1;
}
if(defined($output_file)) {
!-f $output_file or die "Specified output file, '$output_file', already exists";
open($out_fh, '>', $output_file) or die "Couldn't open output file, '$output_file': $!";
}
my $progress = Term::ProgressBar->new({
name => 'file processor',
count => $num_lines,
remove => 1,
fh => $message_fh,
});
while (my $line = <$in_fh>) {
chomp($line);
print $out_fh "I found a line: $line\n";
$progress->message("Found 10000!") if($line =~ /10000/);
$progress->update();
}
$progress->update($num_lines);
print $message_fh "Finished\n";
When the file is defined explicitly, the progress bar displays the linewise progress
through the file. Since the progress bar by default prints output to stderr, your scripts
output to STDOUT will not be affected.
Using Completion Time Estimation
my $progress = Term::ProgressBar->new({
name => 'Powers',
count => $max,
ETA => 'linear',
});
$progress->max_update_rate(1);
my $next_update = 0;
for (0..$max) {
my $is_power = 0;
for (my $i = 0; 2**$i <= $_; $i++) {
if ( 2**$i == $_ ) {
$is_power = 1;
$progress->message(sprintf "Found %8d to be 2 ** %2d", $_, $i);
}
}
$next_update = $progress->update($_)
if $_ > $next_update;
}
$progress->update($max)
if $max >= $next_update;
This example uses the ETA option to switch on completion estimation. Also, the update
return is tuned to try to update the bar approximately once per second, with the
max_update_rate call. See the documentation for the new method for details of the
format(s) used.
This example also provides an example of the use of the message function to output
messages to the same filehandle whilst keeping the progress bar intact
The complete text of this example is in examples/powers5 in the distribution set (it is
not installed as part of the module.
INSTANCE CONSTRUCTION
new
Create & return a new Term::ProgressBar instance.
ARGUMENTS
If one argument is provided, and it is a hashref, then the hash is treated as a set of
key/value pairs, with the following keys; otherwise, it is treated as a number, being
equivalent to the "count" key.
count
The item count. The progress is marked at 100% when update count is invoked, and
proportionally until then.
If you specify a count less than zero, just the name (if specified) will be
displayed and (if the remove flag is set) removed when the progress bar is updated
with a number lower than zero. This allows you to use the progress bar when the
count is sometimes known and sometimes not without making multiple changes
throughout your code.
name
A name to prefix the progress bar with.
fh The filehandle to output to. Defaults to stderr. Do not try to use *foo{THING}
syntax if you want Term capabilities; it does not work. Pass in a globref
instead.
term_width
Sometimes we can't correctly determine the terminal width. You can use this
parameter to force a term width of a particular size. Use a positive integer,
please :)
silent
If passed a true value, Term::ProgressBar will do nothing at all. Useful in
scripts where the progress bar is optional (or just plain doesn't work due to
issues with modules it relies on).
Instead, tell the constructor you want it to be silent and you don't need to
change the rest of your program:
my $progress = Term::ProgressBar->new( { count => $count, silent => $silent } );
# later
$progress->update; # does nothing
ETA A total time estimation to use. If enabled, a time finished estimation is printed
on the RHS (once sufficient updates have been performed to make such an estimation
feasible). Naturally, this is an estimate; no guarantees are made. The format of
the estimate
Note that the format is intended to be as compact as possible while giving over
the relevant information. Depending upon the time remaining, the format is
selected to provide some resolution whilst remaining compact. Since the time
remaining decreases, the format typically changes over time.
As the ETA approaches, the format will state minutes & seconds left. This is
identifiable by the word 'Left' at the RHS of the line. If the ETA is further
away, then an estimate time of completion (rather than time left) is given, and is
identifiable by 'ETA' at the LHS of the ETA box (on the right of the progress
bar). A time or date may be presented; these are of the form of a 24 hour clock,
e.g. '13:33', a time plus days (e.g., ' 7PM+3' for around in over 3 days time) or
a day/date, e.g. ' 1Jan' or '27Feb'.
If ETA is switched on, the return value of update is also affected: the idea here
is that if the progress bar seems to be moving quicker than the eye would normally
care for (and thus a great deal of time is spent doing progress updates rather
than "real" work), the next value is increased to slow it. The maximum rate aimed
for is tunable via the max_update_rate component.
The available values for this are:
undef
Do not do estimation. The default.
linear
Perform linear estimation. This is simply that the amount of time between the
creation of the progress bar and now is divided by the current amount done,
and completion estimated linearly.
EXAMPLES
my $progress = Term::ProgressBar->new(100); # count from 1 to 100
my $progress = Term::ProgressBar->new({ count => 100 }); # same
# Count to 200 thingies, outputting to stdout instead of stderr,
# prefix bar with 'thingy'
my $progress = Term::ProgressBar->new({ count => 200,
fh => \*STDOUT,
name => 'thingy' });
INSTANCE COMPONENTS
Scalar Components.
See "get_set" in Class::MethodMaker for usage.
target
The final target. Updates are measured in terms of this. Changes will have no effect
until the next update, but the next update value should be relative to the new target.
So
$p = Term::ProgressBar({count => 20});
# Halfway
$p->update(10);
# Double scale
$p->target(40)
$p->update(21);
will cause the progress bar to update to 52.5%
max_update_rate
This value is taken as being the maximum speed between updates to aim for. It is only
meaningful if ETA is switched on. It defaults to 0.5, being the number of seconds
between updates.
Boolean Components
See "get_set" in Class::MethodMaker for usage.
minor
Default: set. If unset, no minor scale will be calculated or updated.
Minor characters are used on the progress bar to give the user the idea of progress
even when there are so many more tasks than the terminal is wide that the granularity
would be too great. By default, Term::ProgressBar makes a guess as to when minor
characters would be valuable. However, it may not always guess right, so this method
may be called to force it one way or the other. Of course, the efficiency saving is
minimal unless the client is utilizing the return value of update.
See examples/powers4 and examples/powers3 to see minor characters in action, and not
in action, respectively.
Configuration
lbrack
Left bracket ( defaults to [ )
$progress->lbrack('<');
rbrack
Right bracket ( defaults to ] )
$progress->rbrack('>');
INSTANCE HIGHER-LEVEL PROCEDURES
update
Update the progress bar.
ARGUMENTS
so_far
Current progress point, in whatever units were passed to "new".
If not defined, assumed to be 1+ whatever was the value last time "update" was
called (starting at 0).
RETURNS
next_call
The next value of so_far at which to call "update".
message
Output a message. This is very much like print, but we try not to disturb the terminal.
ARGUMENTS
string
The message to output.
REPORTING BUGS
via RT: <https://rt.cpan.org/Dist/Display.html?Name=Term-ProgressBar>
COMPATIBILITY
If exactly two arguments are provided, then new operates in v1 compatibility mode: the
arguments are considered to be name, and item count. Various other defaults are set to
emulate version one (e.g., the major output character is '#', the bar width is set to 50
characters and the output filehandle is not treated as a terminal). This mode is
deprecated.
AUTHOR
Martyn J. Pearce fluffy@cpan.org
Significant contributions from Ed Avis, amongst others.
MAINTAINER
Gabor Szabo <http://szabgab.com/> <http://perlmaven.com/>
LICENSE AND COPYRIGHT
Copyright (c) 2001, 2002, 2003, 2004, 2005 Martyn J. Pearce. This program is free
software; you can redistribute it and/or modify it under the same terms as Perl itself.