Etydhv

I often have trouble remembering the name of the kpsewhich command. Maybe it would be easier for me to remember it, if I understand where the name come from, so the question is:

What does the kpse stand for?

Karl's Path SEarch Library WHICH

As info kpathsea says (online manual here), Kpathsea is a library for path searching (e.g., for very quickly locating a given .sty file in a set of potentially large TEXMF trees, without doing a recursive directory tree traversal every time a given file is needed; this is important when compiling LaTeX documents using several packages, themselves requiring other packages, possibly various font files, etc.).

This path search gives the pathse part, abbreviated as pse. The “which“ reminds of the Unix which utility, which tells you the path of the executable run for a given command, according to your PATH environment variable. For instance:

$ which find
/usr/bin/find

I believe the “k” stands for “Karl Berry”. :-)

Note: the comparison between which and kpsewhich goes further than that. As Unix shells often maintain a cache of executables present in directories of the PATH in order to offer efficient lookup for completion and program starting, and which performs a query on this cache, the Kpathsea library maintains a filename database (comprised of the ls-R files in each TEXMF tree) in order to offer similar fast lookup to TeX-related programs. In Unix shells, the cache can often be updated with a hash command (hash -r in Bash, rehash in Zsh) when you've added or removed executables from your PATH and wish to refresh the cache without restarting your shell; for the Kpathsea library, the corresponding operation is done with mktexlsr, also known as texhash. Finally, which performs a lookup query on the cache maintained by Unix shells, similarly as kpsewhich on the filename database (kpsewhich is more sophisticated than a typical which though, as it can return different results depending on what was given as -progname, has a notion of variables that can be set in special config files, etc.).