## 2 Installing and Using CFITSIO

First, you should download the CFITSIO software and the set of example FITS utility programs from the web site at https://heasarc.gsfc.nasa.gov/docs/software/fitsio/. The example programs illustrate how to perform many common types of operations on FITS files using CFITSIO. They are also useful when writing a new program because it is often easier to take a copy of one of these utility programs as a template and then modify it for your own purposes, rather than writing the new program completely from scratch.

To build the CFITSIO library on Unix platforms, ‘untar’ the source code distribution file and then execute the following commands in the directory containing the source code:

    >  ./configure [--prefix=/target/installation/path]
    >  make           (or 'make shared')
    >  make install   (this step is optional)

The optional ’prefix’ argument to configure gives the path to the directory where the CFITSIO library and include files should be installed via the later ’make install’ command. For example,

    >  ./configure --prefix=/usr1/local

will cause the ’make install’ command to copy the CFITSIO libcfitsio file to /usr1/local/lib and the necessary include files to /usr1/local/include (assuming of course that the process has permission to write to these directories).

Pre-compiled versions of the CFITSIO DLL library are available for PCs. On Macintosh machines, refer to the README.MacOS file for instructions on building CFITSIO using CodeWarrior.

Any programs that use CFITSIO must of course be linked with the CFITSIO library when creating the executable file. The exact procedure for linking a program depends on your software environment, but on Unix platforms, the command line to compile and link a program will look something like this:

    gcc -o myprog myprog.c -L. -lcfitsio -lm -lnsl -lsocket

You may not need to include all of the ’m’, ’nsl’, and ’socket’ system libraries on your particular machine. To find out what libraries are required on your (Unix) system, type ’make testprog’ and see what libraries are then included on the resulting link line.