You have been zigged (series) : Forking a child process (part 2)

In this blog we will continue modifying last program. We will listen to the exit code and log it to console.

const std = @import("std");

pub fn main(init: std.process.Init) !void {
    const allocator = init.arena.allocator();
    // defer init.arena.deinit();  not needed as zig will deinit main arena on exit anyway
    const args = try init.minimal.args.toSlice(allocator);
    if (args.len == 2 and std.mem.eql(u8, args[1], "--worker=true")) {
        var buffer: [1024]u8 = undefined;
        var file_writer = std.Io.File.Writer.init(.stdout(), init.io, &buffer);
        var stdout_writer = &file_writer.interface;
        try stdout_writer.print("Printing from worker process...\n\n", .{});
        try stdout_writer.flush();
        std.process.exit(1);
    } else {
        var buffer: [1024]u8 = undefined;
        var file_writer = std.Io.File.Writer.init(.stdout(), init.io, &buffer);
        var stdout_writer = &file_writer.interface;
        try stdout_writer.print("Printing from main process...\n\n", .{});
        try stdout_writer.flush();

        const argv = &.{ "./worker__main", "--worker=true" };
        var child = try std.process.spawn(init.io, .{ .argv = argv, .stdout = .inherit });
        const term = try child.wait(init.io);
        switch (term) {
            .exited => |code| {
                try stdout_writer.print("Main: Child exit code is {}\n", .{code});
            },
            .signal => |sig| {
                try stdout_writer.print("Main: OS killed child with {}\n", .{sig});
            },
            .stopped => |signal| {
                try stdout_writer.print("Main: child got stopped/suspended by signal {}\n", .{signal});
            },
            .unknown => |code| {
                try stdout_writer.print("Main: child got terminated abnormally with raw code {}\n", .{code});
            },
        }
        try stdout_writer.flush();
    }
}

We'll build using zig build-exe -O ReleaseSafe worker__main.zig and run using ./worker__main. The output will be

Printing from main process...

Printing from worker process...

Main: Child exit code is 1

Thanks for reading. To be continued,