genrule(
    name = "foo",
    srcs = [],
    outs = ["foo.txt"],
    cmd = "sleep 3 && echo 'Hello Bazel!' > $@ ",
)

# This is a comment?
genrule(
    name = "bar",
    srcs = [],
    outs = ["bar.txt"],
    cmd = "printenv > $@ ",
)