Bashsimplecurses: Simple curses library made in bash to draw terminal interfaces

There&#x27;s some quite impressive and interesting bash (and other shell) exploration in the matrix.org &quot;Fun Shell Scripting&quot; room from time to time; usually when someone asks an obscure question and a few people dive down a rabbit-hole.<p>One oft overlooked feature is bash supports dynamically loadable &#x27;builtins&#x27; as shared object modules so it wouldn&#x27;t take much to create a &#x27;proper&#x27; wrapper around libncurses.<p>Debian and derivatives have the package &quot;bash-builtins&quot; that has a lot of examples including wrapping&#x2F;implementing many coreutils tools.

This is cool, I&#x27;ve used curses UIs to build various small things that need to be a) vaguely easy to use (so, complicated CLIs are out. oncalls need to be able to use this at 3am while half their brain is still sleeping) and b) accessible over ssh because we have secure ssh access to these envs but ~nothing else.<p>So I love TUIs.<p>That said, I&#x27;m always a little puzzled about why people build these libraries in bash. Is it simply curiosity? Maybe, and if so, godspeed.<p>But if it&#x27;s driven by pragmatism, let me assure the reader that if there are limits to the extents I will go to get python somewhere instead of writing even a somewhat nontrivial bash script, I have yet to find them. Not only is bash just kind of really annoying to program in, it&#x27;s also nearly unethical to program in. Let me link the 2 I always link to when someone tells me they&#x27;re &quot;working on&quot; a bash script.<p>Steam deleted my entire system (empty variable expansion): <a href="https:&#x2F;&#x2F;github.com&#x2F;valvesoftware&#x2F;steam-for-linux&#x2F;issues&#x2F;3671">https:&#x2F;&#x2F;github.com&#x2F;valvesoftware&#x2F;steam-for-linux&#x2F;issues&#x2F;3671</a><p>Bumblebee deletes &#x2F;usr due to space: <a href="https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;softwaregore&#x2F;comments&#x2F;2hsdo6&#x2F;giant_bug_causing_usr_to_be_deleted_so_sorry&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;softwaregore&#x2F;comments&#x2F;2hsdo6&#x2F;giant_...</a><p>So I warn people: if you use python, you&#x27;ll categorically avoid being the third entry in my list.

Zsh users get a bundled curses module; see zsh&#x2F;curses¹ in zshmodules(1). It is a <i>very</i> thin wrapper, so it works how you&#x27;d expect from other uses. There is a tetris implementation using zsh&#x2F;curses that ships with zsh², and you can use it as a nice comparison to the non-curses implementation that also comes with zsh³.<p>I&#x27;ve used zsh&#x2F;curses a few times to hack together little interfaces, and it is quite workable. It makes things far simpler once you start reaching for terminfo&#x27;s capabilities that require you to think about state too much. A friend of mine wrote a little mblaze⁴ frontend using it, and it felt like using single mailbox mutt with less than a hundred lines of code.<p>I was expecting the linked project to be a loadable module too given that bash also supports them, but it is actually a little more interesting to look at given it implements a bunch of the behaviour itself on top of tput calls.<p>¹ <a href="https:&#x2F;&#x2F;zsh.sourceforge.io&#x2F;Doc&#x2F;Release&#x2F;Zsh-Modules.html#The-zsh_002fcurses-Module" rel="nofollow">https:&#x2F;&#x2F;zsh.sourceforge.io&#x2F;Doc&#x2F;Release&#x2F;Zsh-Modules.html#The-...</a><p>² <a href="https:&#x2F;&#x2F;github.com&#x2F;zsh-users&#x2F;zsh&#x2F;blob&#x2F;master&#x2F;Functions&#x2F;Misc&#x2F;tetriscurses">https:&#x2F;&#x2F;github.com&#x2F;zsh-users&#x2F;zsh&#x2F;blob&#x2F;master&#x2F;Functions&#x2F;Misc&#x2F;...</a><p>³ <a href="https:&#x2F;&#x2F;github.com&#x2F;zsh-users&#x2F;zsh&#x2F;blob&#x2F;master&#x2F;Functions&#x2F;Misc&#x2F;tetris">https:&#x2F;&#x2F;github.com&#x2F;zsh-users&#x2F;zsh&#x2F;blob&#x2F;master&#x2F;Functions&#x2F;Misc&#x2F;...</a><p>⁴ <a href="https:&#x2F;&#x2F;git.vuxu.org&#x2F;mblaze&#x2F;about&#x2F;" rel="nofollow">https:&#x2F;&#x2F;git.vuxu.org&#x2F;mblaze&#x2F;about&#x2F;</a>

I have a fondness for bash abuse and those odd sort of people who get fixated on bash. bed [0] the bash editor is one of my favorite examples, always surprised by how short and concise it is, far from a great editor but a great exercise and I learned a thing or two about the bash way from it.<p>0. <a href="https:&#x2F;&#x2F;github.com&#x2F;comfies&#x2F;bed">https:&#x2F;&#x2F;github.com&#x2F;comfies&#x2F;bed</a>

I&#x27;ve made a similar library called bash-term[1], which is similar, but only has functions for lower-level operations, like moving the cursor to the end of the line, etc. It&#x27;s also cleaner and has almost no global variables.<p>[1] <a href="https:&#x2F;&#x2F;github.com&#x2F;bash-bastion&#x2F;bash-term">https:&#x2F;&#x2F;github.com&#x2F;bash-bastion&#x2F;bash-term</a>

If you only need simple dialogs, <i>whiptail</i> is usually installed on Debian-based systems: <a href="https:&#x2F;&#x2F;en.wikibooks.org&#x2F;wiki&#x2F;Bash_Shell_Scripting&#x2F;Whiptail" rel="nofollow">https:&#x2F;&#x2F;en.wikibooks.org&#x2F;wiki&#x2F;Bash_Shell_Scripting&#x2F;Whiptail</a>

Bash with a #!&#x2F;bin&#x2F;bash shebang. Typical GNU cultural imperialism. &quot;Everyone has a Bash and it&#x27;s always kept in &#x2F;bin.&quot;

If the only purpose of this project is to create windows in Bash one might easily replace it with tmux panes.

This reminds me of something I have always wanted in the UNIX ecosystem:<p>&quot;topify&quot;<p>... which is the word I would use to describe a primitive that will take line inputs from stdio and display them in a &#x27;top&#x27; style output, presumably with curses.<p>Maybe there is more complication here than I have thought out but ... if I can output a standard line with columns I have already defined (perhaps in an &#x27;awk&#x27; pipeline or whatever) then I would like a way to refresh them, in some order.<p>I am fairly certain this does not exist ...