Here is the README.SxP4 from that tgz file:
This is the README file from SxP4Test_linux_patch.tgz . The files in this archive are for compiling the SxP4Test software, available at http://www.zeptomoby.com/satellites/SxP4Test.zip, in a Linux build environment. The files in SxP4Test.zip appear to be for a Windows Visual Studio or .NET environment build environment. The SxP4Test.zip file, when extracted, creates two directories, 'norad' and 'SxP4Test'. The files provided here are a single patch file for the original sources, and simple Makefiles for each of the original subdirectories. This tar file should be extracted in the directory that contains the 'norad' and 'SxP4Test' directories, and will create: norad/Makefile SxP4Test/Makefile SxP4.patch README.SxP4 The 'norad' Makefile builds a static library, 'norad.a', that contains routines implementing the SGP4/SPD4 algorithms. The 'SxP4Test' Makefile builds an example program, SxP4Test, that demonstrates the use of routines in the norad library. The linux patch/build process: 1. Download 'SxP4Test.zip' from http://www.zeptomoby.com/satellites/ and extract the contents to a directory of your choice, for example, ./SxP4 2. Place this tar file in that same directory and extract the contents $ cd SxP4 $ cp <tarfile-path>/SxP4_linux_patch.tgz . $ tar xzf SxP4_linux_patch.tgz 3. Apply the patch file in place thusly: $ patch -p1 < SxP4.patch 4. In the 'norad' subdirectory, simply do 'make'. 5. Ditto in the 'SxP4Test' subdirectory. The resulting executable 'SxP4Test', when invoked, prints out orbital data from TLEs hardwired in the source.