Building up on the file example, we can create a rule that builds and runs a simple executable shell script.

Rename the rule #

To begin with, let’s rename the rule as it is customary in Bazel to postfix the executable rules with _binary. Our BUILD file will now be:

load(":rules.bzl", "demo_binary")

demo_binary(name = "executable")

Renaming the functions in rules.bzl is trivial:

def _demo_binary_impl(ctx):
    ...

demo_binary = rule(
    implementation = _demo_binary_impl,
    ...

Create a script #

We can now change the generated file to a shell script

def _demo_binary_impl(ctx):
    out = ctx.actions.declare_file("hello")
    ctx.actions.write(
        output = out,
        content = "#!/bin/sh\necho \"Hello, World!\"\n",
    )
    ...

Make the rule executable #

Finally, we mark the rule as an executable and specify the our script as the executable file:

def _demo_binary_impl(ctx):
    ...
    return [DefaultInfo(
        files = depset([out]),
        executable = out,
    )]

demo_binary = rule(
    implementation = _demo_binary_impl,
    executable = True,
)

Build and run #

We can now build the file as we did before:

$ bazel build //executable
...
Target //executable:executable up-to-date:
  bazel-bin/executable/hello
...

We can use Bazel to run it as well:

$ bazel run //executable
...
Target //executable:executable up-to-date:
  bazel-bin/executable/hello
...
Hello, World!

We can also run the script directly:

$ bazel-bin/executable/hello
Hello, World!

The complete example is here.