update

README.md

@@ -1,5 +1,60 @@
-# ctempd
+# Screen Color Temperature Changing Daemon
 
-Small daemon to set screen temperature.  ctempd can either set the screen's
-temperature once with the -s option or run in the background and set the
+Small daemon to set screen temperature.  ctempd can either set the screen's temperature once with the -s option or run in the background and set the
 screen's temperature automatically based on the time of day.
+
+## Features
+
+* Set screen temperature continuously in the background
+* Set screen temperature once
+
+## Installation
+
+ctempd is written in C and known to work on the operating systems listed in the table below.  To compile it you need the following things:
+
+* A recent C compiler (tested with both clang >= 11 and GCC >= 8)
+* make (tested with both BSD and GNU make)
+* [libXrandr](https://www.x.org/wiki/libraries/libxrandr/)
+* [libX11 core development libraries](https://www.x.org/releases/current/doc/libX11/libX11/libX11.html)
+
+### Dependencies
+
+Install the dependencies as follows:
+
+| Operating System | Commands and Notes |
+| --- | --- |
+| OpenBSD | All installed by default |
+| Void Linux| `xbps-install gcc make libXrandr-devel libX11-devel` |
+
+If your operating system does not have `pkg-config` installed by default, you have to install it as well.
+
+### Compilation and Installation
+
+By default, the `Makefile` looks for external includes and libraries in `/usr/local/{include,lib}`, `/usr/X11R6/{include,lib}`.  If your distribution uses special path, you have to modify the Makefile accordingly.
+
+Compile and install with the following commands:
+
+```
+$ make
+# make install
+```
+
+## Usage
+
+Let ctempd automatically adapt the screen temperature based on the time of day.  The highest temperature at noon is 5400K:
+
+```
+$ ctempd 5400
+```
+
+ctempd logs via syslog, you can check the current temperature in your system's log messages.
+
+Set the screen temperature to 3200K once.
+
+```
+$ ctempd -s 3200
+```
+
+## License
+
+isscrolls was written by Matthias Schmidt and is public domain.  The algorithm to set the screen temperature was written by Ted Unangst and is also public domain.