Tuesday, July 5, 2011


[EDIT] This code is now available on github: libpbar

cURL ships with one. wget uses it's own. OpenSSH (scp) even comes with it's own version. Indeed, I've written several variations myself over the years. Sooner or later, if you are doing something that processes large amounts of data or takes a long time to complete and you are working in a command-line environment you will write your own, too. A progress bar.

I did a quick search for existing progress bar libraries but came up with little outside of Ruby and Python wrappers around what the packages I mention above are already doing [1]. For mostly selfish reasons, I've decided to write a library that fixes my redundant behavior moving forward. Once I am able to provide a proper build system I will put this code up on github - my unfamiliarity with autotools may delay this a bit.

What this library aims to provide is a consistent interface for programatically displaying a progress bar outside of a GUI environment. It does not try to provide a package similar to Pipe Viewer (pv) which is a complete, standalone program for monitoring processes activity. Instead, to keep things simple, libpbar will initially provide a class with the following public interface:

class ProgressBar {
    ProgressBar (::size_t cap);
    void update (::size_t n = 1);

With three implementations provided with the library: TextProgressBar, ColorProgressBar, GraphicalProgressBar. These provide basic text functionality, color text, and a GTK+-based object respectively. Using any of these facilities is as simple as:

int flags = TextProgressBar::SHOW_VALUE | TextProgressBar::SHOW_COUNT;
TextProgressBar pb(100,flags);

They each do as you might expect:



The nice thing about the GUI version is that the hosting program doesn't need to be a GUI application. For this version of the progress bar a separate thread is used to spawn the graphical interface and as much as possible is done to shed the window treatments to expose just the progress bar itself.

I've got to expand on this by allowing some way to encode message text with format strings and allowing user-defined color modifications. The basics are there, however, and I should now be free from writing yet another progress bar implementation.

[1] This is a solved problem and certainly my fruitless search does not imply any lack of existing tools

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