External program output into build

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1

I want to embed the git version into my program. What I tried to do is:

    const get_command_output = b.addSystemCommand(&.{ "git", "rev-parse", "--short", "HEAD" });
    const git_version = get_command_output.captureStdOut();
    options.addOption([]const u8, "git_version", git_version);

but I get the following error:

build.zig:172:50: error: expected type '[]const u8', found 'Build.LazyPath'
    options.addOption([]const u8, "git_version", git_version);

There is another way to do it, get the git command to output to a file and then @embedFile to get the string value, but I think my current approach is cleaner.

Thanks

2

We do std.mem.trimRight(u8, b.run(&.{ "git", "rev-parse", "--verify", "HEAD" }), "\n") which means git rev-parse is run on every configure, which is not great in theory, but ok in practice.

The neat way to do this is to depend on ./git/logs/HEAD:

Otherwise, I don’t think there’s an automatic way to do what you want to do here, but it is possible by writing your own Options step.

3

Yeah, Zig itself also does that at configure time, so it’s officially fine :stuck_out_tongue:

4
5

Yes, that is neat, but probably more than I need right now, unless you have an easy way to add it to a build.zig file.

Thanks also for the pointer to b.run() - it works.

6

I finally settled on:

    const git_version = b.run(&.{ "git", "log",
                  "--pretty=format:%cI-%h", "-1" });

Which has the commit time as well as the uid, which makes it easier to find, and reason about ordering.

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