本页面将介绍输出目录的要求和布局。
要求
输出目录布局的要求：
- 如果多个用户在同一框上进行构建，则不会冲突。
- 支持同时在多个工作区中构建。
- 支持在同一工作区中针对多个目标配置进行构建。
- 不会与任何其他工具发生冲突。
- 易于访问。
- 易于清洁，即便是精心挑选也无妨。
- 明确化，即使用户在切换到客户端目录时依赖符号链接也是如此。
- 每位用户的所有构建状态都应在一个目录下（“我想从所有客户端中清除所有 .o 文件”）。
当前布局
目前实现的解决方案：
- Bazel 必须从包含 WORKSPACE 文件的目录（“工作区目录”）或其子目录调用。否则，它会报告错误。
- 在 Linux 上，outputRoot 目录默认为
~/.cache/bazel；在 macOS 上，则默认为/private/var/tmp；如果在 Windows 上，则默认为 ；如果已设置，则为%USERPROFILE%；否则为在设置了FOLDERID_Profile标志的情况下调用SHGetKnownFolderPath()的结果。如果已设置环境变量$TEST_TMPDIR（例如在 Bazel 本身测试中），则该值会替换默认值。 - Bazel 用户的构建状态位于
outputRoot/_bazel_$USER下。这称为 outputUserRoot 目录。 outputUserRoot目录下面有一个install目录，它是一个installBase目录，其名称是 Bazel 安装清单的 MD5 哈希。- 在
outputUserRoot目录下，系统还会创建一个outputBase目录，其名称是工作区路径的 MD5 哈希。例如，如果 Bazel 在工作区目录/home/user/src/my-project（或与该目录符号关联的目录）中运行，系统会创建一个名为/home/user/.cache/bazel/_bazel_user/7ffd56a6e4cb724ea575aba15733d113的输出基目录。您还可以在 Bazel 工作区中运行echo -n $(pwd) | md5sum，以获取 MD5。 - 您可以使用 Bazel 的
--output_base启动选项来替换默认输出基目录。例如bazel --output_base=/tmp/bazel/output build x/y:z。 - 您也可以使用 Bazel 的
--output_user_root启动选项替换默认安装基目录和输出基目录。例如：bazel --output_user_root=/tmp/bazel build x/y:z。
“bazel-<workspace-name>”、“bazel-out”、“bazel-testlogs”和“bazel-bin”的符号链接放在工作区目录中；这些符号链接指向输出目录内目标专用目录中的某些目录。这些符号链接只是为了方便用户，因为 Bazel 本身并不使用它们。此外，仅当工作区目录可写时，系统才会执行此操作。
布局示意图
目录布局如下：
<workspace-name>/ <== The workspace directory
bazel-my-project => <...my-project> <== Symlink to execRoot
bazel-out => <...bin> <== Convenience symlink to outputPath
bazel-bin => <...bin> <== Convenience symlink to most recent written bin dir $(BINDIR)
bazel-testlogs => <...testlogs> <== Convenience symlink to the test logs directory
/home/user/.cache/bazel/ <== Root for all Bazel output on a machine: outputRoot
_bazel_$USER/ <== Top level directory for a given user depends on the user name:
outputUserRoot
install/
fba9a2c87ee9589d72889caf082f1029/ <== Hash of the Bazel install manifest: installBase
_embedded_binaries/ <== Contains binaries and scripts unpacked from the data section of
the bazel executable on first run (such as helper scripts and the
main Java file BazelServer_deploy.jar)
7ffd56a6e4cb724ea575aba15733d113/ <== Hash of the client's workspace directory (such as
/home/user/src/my-project): outputBase
action_cache/ <== Action cache directory hierarchy
This contains the persistent record of the file
metadata (timestamps, and perhaps eventually also MD5
sums) used by the FilesystemValueChecker.
action_outs/ <== Action output directory. This contains a file with the
stdout/stderr for every action from the most recent
bazel run that produced output.
command.log <== A copy of the stdout/stderr output from the most
recent bazel command.
external/ <== The directory that remote repositories are
downloaded/symlinked into.
server/ <== The Bazel server puts all server-related files (such
as socket file, logs, etc) here.
jvm.out <== The debugging output for the server.
execroot/ <== The working directory for all actions. For special
cases such as sandboxing and remote execution, the
actions run in a directory that mimics execroot.
Implementation details, such as where the directories
are created, are intentionally hidden from the action.
Every action can access its inputs and outputs relative
to the execroot directory.
<workspace-name>/ <== Working tree for the Bazel build & root of symlink forest: execRoot
_bin/ <== Helper tools are linked from or copied to here.
bazel-out/ <== All actual output of the build is under here: outputPath
local_linux-fastbuild/ <== one subdirectory per unique target BuildConfiguration instance;
this is currently encoded
bin/ <== Bazel outputs binaries for target configuration here: $(BINDIR)
foo/bar/_objs/baz/ <== Object files for a cc_* rule named //foo/bar:baz
foo/bar/baz1.o <== Object files from source //foo/bar:baz1.cc
other_package/other.o <== Object files from source //other_package:other.cc
foo/bar/baz <== foo/bar/baz might be the artifact generated by a cc_binary named
//foo/bar:baz
foo/bar/baz.runfiles/ <== The runfiles symlink farm for the //foo/bar:baz executable.
MANIFEST
<workspace-name>/
...
genfiles/ <== Bazel puts generated source for the target configuration here:
$(GENDIR)
foo/bar.h such as foo/bar.h might be a headerfile generated by //foo:bargen
testlogs/ <== Bazel internal test runner puts test log files here
foo/bartest.log such as foo/bar.log might be an output of the //foo:bartest test with
foo/bartest.status foo/bartest.status containing exit status of the test (such as
PASSED or FAILED (Exit 1), etc)
include/ <== a tree with include symlinks, generated as needed. The
bazel-include symlinks point to here. This is used for
linkstamp stuff, etc.
host/ <== BuildConfiguration for build host (user's workstation), for
building prerequisite tools, that will be used in later stages
of the build (ex: Protocol Compiler)
<packages>/ <== Packages referenced in the build appear as if under a regular workspace
*.runfiles 目录的布局在 RunfilesSupport 所指向的位置有更详细的说明。
bazel clean
bazel clean 对 outputPath 和 action_cache 目录执行 rm -rf。还会移除工作区符号链接。--expunge 选项将清理整个 outputBase。