setUpChild

fn setUpChild(ev: *Evented, options: struct {
    stdin_pipe: c.fd_t,
    stdout_pipe: c.fd_t,
    stderr_pipe: c.fd_t,
    dev_null_fd: c.fd_t,
    prog_pipe: c.fd_t,
    argv_buf: [:null]?[*:0]const u8,
    env_block: process.Environ.Block,
    PATH: []const u8,
    spawn: process.SpawnOptions,
}) ForkBailError {
    try ev.setUpChildIo(
        options.spawn.stdin,
        options.stdin_pipe,
        c.STDIN_FILENO,
        options.dev_null_fd,
    );
    try ev.setUpChildIo(
        options.spawn.stdout,
        options.stdout_pipe,
        c.STDOUT_FILENO,
        options.dev_null_fd,
    );
    try ev.setUpChildIo(
        options.spawn.stderr,
        options.stderr_pipe,
        c.STDERR_FILENO,
        options.dev_null_fd,
    );

    switch (options.spawn.cwd) {
        .inherit => {},
        .dir => |cwd_dir| try processSetCurrentDir(ev, cwd_dir),
        .path => |cwd_path| try processSetCurrentPath(ev, cwd_path),
    }

    // Must happen after fchdir above, the cwd file descriptor might be
    // equal to prog_fileno and be clobbered by this dup2 call.
    if (options.prog_pipe != -1) try ev.dup2(options.prog_pipe, prog_fileno);

    if (options.spawn.gid) |gid| while (true) switch (c.errno(c.setregid(gid, gid))) {
        .SUCCESS => break,
        .INTR => {},
        .AGAIN => return error.ResourceLimitReached,
        .INVAL => return error.InvalidUserId,
        .PERM => return error.PermissionDenied,
        else => return error.Unexpected,
    };

    if (options.spawn.uid) |uid| while (true) switch (c.errno(c.setreuid(uid, uid))) {
        .SUCCESS => break,
        .INTR => {},
        .AGAIN => return error.ResourceLimitReached,
        .INVAL => return error.InvalidUserId,
        .PERM => return error.PermissionDenied,
        else => return error.Unexpected,
    };

    if (options.spawn.pgid) |pid| while (true) switch (c.errno(c.setpgid(0, pid))) {
        .SUCCESS => break,
        .INTR => {},
        .ACCES => return error.ProcessAlreadyExec,
        .INVAL => return error.InvalidProcessGroupId,
        .PERM => return error.PermissionDenied,
        else => return error.Unexpected,
    };

    if (options.spawn.start_suspended) while (true) switch (c.errno(c.kill(0, .STOP))) {
        .SUCCESS => break,
        .INTR => {},
        .PERM => return error.PermissionDenied,
        else => return error.Unexpected,
    };

    return ev.execv(
        options.spawn.expand_arg0,
        options.argv_buf.ptr[0].?,
        options.argv_buf.ptr,
        options.env_block,
        options.PATH,
    );
}