This chapter will try to cover all the needed knowledge to write a new patchset for autoepatch, as well as to maintain the ones already present in the distribution. An autoepatch patchset consists at least of two atoms: a directory, whose name is also the name of the patchset, and a bash script, inside that directory, named the same way with ".sh" extension. That script is the core of the patchset, as it will tell autoepatch where to find the files to patch, what kind of patchset it is, and whether to fail or not if the patching is not completed as intended. To facilitate writing new patchsets, the names of the functions that are defined into the patchset's script are standardised, so that the parameters they get and the result they echo out can be relied upon and used by autoepatch safely. patch_targets This function is the basis to start writing a new patchset, it is used to identify where the patches are going to be applied. The results are simply returned on the standard output, one per line. This function is supposed to check if the patch should or should not be applied over a file or a directory, by grepping, if needed, for key phrases that would show if the patch is needed or not. This function is not supposed to check for the applicability of the patch on the current system. The reason for this is that it's way simpler to test all patchsets every time, so that if errors are added to the patchset, they can be fixed immediately. patch_required This function is called in the case the patchset failed to apply entirely; it is supposed to return 0 (truth value) if the patch is important, and autoepatch has to fail if it's not applied (and thus stop the merge process), or 1 (untruth value) if the patch is optional and/or it's not of first importance for the current setup. The reason to have this function is that some patches might be only needed on some targets (for instance Gentoo/FreeBSD, or uClibc or Darwin systems), or only in some situations (newer autotools, newer glibc or linux-headers), and for the rest of the cases, it's just an assurance and a testing purpose to apply the patch on every use. So the failure on autoepatch, when a patchset fails to apply, is entirely decided by the value returned by this function.