add installation and usage info to readme

blocks/README.md

@@ -1,3 +1,52 @@
 # rwmblocks
 status bar for dwm or rwm ported from
 [dwmblocks](https://github.com/torrinfail/dwmblocks)
+
+## Installation
+Unlike `rwm` itself, `rwmblocks` works pretty well, and I plan to replace
+dwmblocks in my config. Install with make:
+
+``` shell
+make install
+```
+
+I don't think this one requires nightly, but you will probably need X11
+installed on your system.
+
+## Usage
+Before installation, configure your status bar by editing `config.rs`. Each
+`Block` entry is one section of the status bar. Unfortunately, Rust's `Command`
+API doesn't expand special shell characters like `~`, so the `command` paths
+need to be absolute. I recommend storing the command in a script so that you can
+edit the command without recompiling `rwmblocks`. For example, my `time` script
+is a very thin wrapper around `date`:
+
+``` shell
+#!/bin/sh
+
+date '+%a %b %d %Y %H:%M |'
+```
+
+while my `mail` and `weather` scripts are a bit more involved.
+
+The `icon` is displayed before command output, the `interval` is how often the
+block is updated in seconds, and `signal` is a signal sent to `rwmblocks` to
+trigger an immediate update for the block. This can be useful if you have
+something like a volume icon, for example, that doesn't need to update on an
+interval but should update when you run some other script. To send such a
+signal, you can use `pkill` as shown below.
+
+``` shell
+pkill -RTMIN+12 rwmblocks
+```
+
+`SIGRTMIN` is the minimum real-time signal reserved for applications, so the
+`signal` fields in `Blocks` are relative to this minimum. Fortunately, `pkill`
+also knows about this convention and allows you to use the syntax shown above.
+This command would trigger an immediate update of my weather block.
+
+After this configuration and installation, simply spawn `rwmblocks` before
+running your window manager. I do this in my `.xinitrc` with `rwmblocks &>
+~/.log/blocks.log &`. If you copy this command, make sure the `.log` directory
+exists in your `$HOME` directory.
+