And if you just don't want to be bothered by locales, it's not enough to setlocale(LC_ALL, "C"); Other libraries may call setlocale() behind your back (e.g. GT

And if you just don't want to be bothered by locales, it's not enough to setlocale(LC_ALL, "C"); Other libraries may call setlocale() behind your back (e.g. GTK2). So, what you have to do is, you have to break setlocale's arms off: #define _GNU_SOURCE #include <stdio.h> #include <dlfcn.h> #include <locale.h> typedef char *(*setlocale_prototype)(int category, const char *locale); static setlocale_prototype real_setlocale = NULL; static char *the_only_locale = "C"; char *setlocale(__attribute__((unused)) int category, __attribute__((unused)) const char *locale) { char *msg; if (!real_setlocale) { *(void **) &real_setlocale = dlsym(RTLD_NEXT, "setlocale"); msg = dlerror(); if (msg) { fprintf(stderr, "Failed to override setlocale(): %s\n", msg); fflush(stderr); real_setlocale = NULL; return the_only_locale; } } /* C is the locale, and the locale shall be C */ return real_setlocale(LC_ALL, "C"); } Now it doesn't matter if GTK or whatever library calls setlocale() with whatever weird parameters, the locale shall be "C".