> An absolute path is going to assume others have the same setup. Certain absolute path locations are standardized by POSIX. Including the absolute path of /us

> An absolute path is going to assume others have the same setup. Certain absolute path locations are standardized by POSIX. Including the absolute path of /usr/bin/env. > and that the program might be a different version than expected (which an absolute path doesn't solve either). ...and those programs in those standard locations are required by those same standards to behave ABI-compatibly with their behavior at time of standardization. Which is why e.g. /bin/bash bothers to strip out features when called as /bin/sh — the interpreter at /bin/sh must be no less and no more than the particular feature-set of the Bourne shell version that POSIX was standardized upon.