On SuSE 10.3 there is a /usr/bin/[ executable (yes, the name of the program is simply the open square bracket). Doing a little research: file /usr/bin/[ /usr/bin/[: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped Is this how BASH implements [ ?