Besides the fact that all the programs share some functions that were explained in Library, everything else about each program is completely independent.
Recall that Gnuastro is written for an active astronomer/scientist (not a passive one who just uses a software).
It must thus be easily navigable.
Hence there are fixed source files (that contain fixed operations) that must be present in all programs, these are discussed fully in Mandatory source code files.
To easily understand the explanations in this section you can use The TEMPLATE program which contains the bare minimum code for one working program.
This template can also be used to easily add new utilities: just copy and paste the directory and change TEMPLATE with your program’s name.
GNU Astronomy Utilities 0.22 manual, February 2024.