The following files are not sorted by name correctly: c_cathode_time.C c_cathode_time.pdf c_cathode_time.png cell8_out.root c_feast_t0.C c_feast_t0.pdf c_feast_t0.png This is the order in which they appear in Thunar. The order should be either cell8_out.root c_cathode_time.C c_cathode_time.pdf c_cathode_time.png c_feast_t0.C c_feast_t0.pdf c_feast_t0.png or c_cathode_time.C c_cathode_time.pdf c_cathode_time.png c_feast_t0.C c_feast_t0.pdf c_feast_t0.png cell8_out.root depending on whether you consider the "_" character to come before "a" or after "z"... Usually it is considered to come before "a".
Actually the underscore is ignored while sorting the files. This is not Thunar's doing, even Nemo, Nautilus and ls have the same behavior while sorting the filenames from your example. From a quick Google I learned that this sorting is determined by LC_COLLATE, see for yourself: pkill -i thunar; LC_COLLATE=c thunar
Is this an environment variable? To use this, do I put LC_COLLATE=c in my bashrc or something?
Yes, it's an environment variable. In the example I provided, it's set only for running thunar, but to make it permanent please refer to Arch's wiki: https://wiki.archlinux.org/index.php/environment_variables Here you can find more info about LC_COLLATE and Locale in general: https://wiki.archlinux.org/index.php/locale#LC_COLLATE:_collation