Rust is a compiled language. How can I run a program directly from the
shell?
The answer is Unix abuse, and a program that is valid in both
Rust and shell.
What I want the program to do from the shell is to compile itself, run
that compiled version, then erase the compiled version and exit. And
the directives to do that can't interfere with the actual Rust.
Fortunately Rust comments start with a double slash, and # indicates a
macro directive which will be ignored if not understood. So at the top
of the program:
#! /bin/sh
//usr/bin/env rustc --test $0 -o ${0}x && ./${0}x; rm -f ${0}x ; exit
The shell script finds and runs the Rust compiler, in test mode,
against itself, generating an executable (its own filename, as it
might be foo.rs, with an "x" on the end on the basis that that's easy
to work out). If that was successful, it runs the executable. Then it
removes it (using -f to avoid errors in case compilation wasn't
successful) and stops before the shell starts trying to interpret Rust
code. All of this is regarded by rustc as irrelevance.
I don't usually play the programming games like quines, Perl golf, and
such, but this one has some actual use: I can run foo.rs, and get back
either compilation errors or the output of the program, just as I do
for the other languages in the weekly challenge.
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