I have the following directory structure:
my_dir
|
--> src
| |
| --> foo.cc
| --> BUILD
|
--> WORKSPACE
|
--> bazel-out/ (symlink)
|
| ...
src/BUILD
contains the following code:
cc_binary(
name = "foo",
srcs = ["foo.cc"]
)
The file foo.cc
creates a file named bar.txt
using the regular way with <fstream>
utilities.
However, when I invoke Bazel with bazel run //src:foo
the file bar.txt
is created and placed in bazel-out/darwin-fastbuild/bin/src/foo.runfiles/foo/bar.txt
instead of my_dir/src/bar.txt
, where the original source is.
I tried adding an outs
field to the foo
rule, but Bazel complained that outs
is not a recognized attribute for cc_binary
.
I also thought of creating a filegroup
rule, but there is no deps
field where I can declare foo
as a dependency for those files.
How can I make sure that the files generated by running the cc_binary
rule are placed in my_dir/src/bar.txt
instead of bazel-out/...
?
Bazel doesn't allow you to modify the state of your workspace, by design.
The short answer is that you don't want the results of the past builds to modify the state of your workspace, hence potentially modifying the results of the future builds. It'll violate reproducibility if running Bazel multiple times on the same workspace results in different outputs.
Given your example: imagine calling bazel run //src:foo
which inserts
#define true false
#define false true
at the top of the src/foo.cc
. What happens if you call bazel run //src:foo
again?
The long answer: https://docs.bazel.build/versions/master/rule-challenges.html#assumption-aim-for-correctness-throughput-ease-of-use-latency
Here's more information on the output directory: https://docs.bazel.build/versions/master/output_directories.html#documentation-of-the-current-bazel-output-directory-layout
There could be a workaround to use genrule. Below is an example that I use genrule to copy a file to the .git folder.
genrule(
name = "precommit",
srcs = glob(["git/**"]),
outs = ["precommit.txt"],
# folder contain this BUILD.bazel file is tool which will be symbol linked, we use cd -P to get to the physical path
cmd = "echo 'setup pre-commit.sh' > $(OUTS) && cd -P tools && ./path/to/your-script.sh",
local = 1, # required
)
If you're passing the name of the output file in when running, you can simply use absolute paths. To make this easier, you can use the realpath
utility if you're in linux. If you're on a mac, it is included in brew install coreutils
. Then running it looks something like:
bazel run my_app_dir:binary_target -- --output_file=`realpath relative/path/to.output