Shell rules for Bazel
This project extends Bazel with a toolchain for common shell commands.
Setup
See the WORKSPACE setup section of the current release.
Or use the following template in your WORKSPACE file to install a development
version of rules_sh:
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "rules_sh",
# Replace git revision and sha256.
sha256 = "0000000000000000000000000000000000000000000000000000000000000000",
strip_prefix = "rules_sh-0000000000000000000000000000000000000000",
urls = ["https://github.com/tweag/rules_sh/archive/0000000000000000000000000000000000000000.tar.gz"],
)
load("@rules_sh//sh:repositories.bzl", "rules_sh_dependencies")
rules_sh_dependencies()Usage
Configure the toolchain
Add the following to your WORKSPACE file to configure a local POSIX toolchain.
load("@rules_sh//sh:posix.bzl", "sh_posix_configure")
sh_posix_configure()Bazel will query PATH for common Unix shell commands. You can override the
path to individual commands with environment variables of the form
POSIX_<COMMAND_NAME>. E.g. POSIX_MAKE=/usr/bin/gmake.
Note, this introduces an inhermeticity to the build as the contents of PATH
may be specific to your machine's setup.
Refer to rules_nixpkgs's nixpkgs_posix_configure for a
hermetic alternative.
Use Unix tools in genrules
The POSIX toolchain exposes custom make variables of the form
POSIX_<COMMAND_NAME> for discovered commands. Use these as follows:
genrule(
name = "example",
srcs = [":some-input-file"],
outs = ["some-output-file"],
cmd = "$(POSIX_GREP) some-pattern $(execpath :some-input-file.bzl) > $(OUTS)",
toolchains = ["@rules_sh//sh/posix:make_variables"],
)See posix.commands defined in @rules_sh//sh/posix.bzl for the list of known
POSIX commands.
Use Unix tools in custom rules
The POSIX toolchain provides two attributes:
commands: Adictmapping names of commands to their paths.paths: A deduplicated list of bindir paths suitable for generating$PATH.
def _my_rule_impl(ctx):
posix_info = ctx.toolchains["@rules_sh//sh/posix:toolchain_type"]
ctx.actions.run(
executable = posix_info.commands["grep"],
...
)
ctx.actions.run_shell(
command = "grep ...",
env = {"PATH": ":".join(posix_info.paths)},
...
)
my_rule = rule(
_my_rule_impl,
toolchains = ["@rules_sh//sh/posix:toolchain_type"],
...
)