Scriptable Zig

There is a preamble you can add to any Zig file to make it runnable as a script.

#if 0
p=$(mktemp -t tmp.XXXXXXXXXX.zig)
cc -x c -E -P $0 > $p
zig run $p
exit $?
#endif

const std = @import("std");

pub fn main() !void {
    std.log.info("hello world!", .{});
}

Then after a quick chmod +x ./script.zig it works even without a sh prefix:

$ ./script.zig
info: hello world!

Now this a long ways from perhaps only needing a shebang but it is indeed functional today 🎉.

The meat here could almost be a one-liner in zig run <(cc -x c -E -P $0) but that resulted in Zig erroring with error: unrecognized file extension of parameter '/dev/fd/63' since zig run works with both Zig and C and C++ and Asm.

You can try adding -x zig but then you get error: language not recognized: 'zig' since -x mainly forwards to the embedded C compiler. (maybe that’s an enhancement worth adding 😉)

Ah trying this with C it seems not being a one-liner also gets around error: failed to check cache: '/dev/fd/63' file_hash Unseekable which is indeed tricky.

This post was inspired by https://www.reddit.com/r/C_Programming/comments/1x2k1y0/compiling_c_is_so_fast_that_i_use_it_as_a/pf37mie/.

Using $0 and mktemp allows this method to be recursive such that Zig scripts can call each other and not clobber sources when printing stack traces after something goes wrong.

exit $? forwards the zig run result to the parent environment.

TIL shebangs don’t even need to be #!. This works too:

//usr/bin/env zig run $0 -- $@; exit

const std = @import("std");

pub fn main() !void {
    std.log.info("hello world!", .{});
    std.os.linux.exit(1);
}

Happy coding!