Output Directory Layout

This page covers requirements and layout for output directories.

Requirements for an output directory layout:

Doesn’t collide if multiple users are building on the same box.如果多个用户在同一个盒子上建造则不会发生冲突。

Supports building in multiple workspaces at the same time.支持同时在多个工作区中构建。
Supports building for multiple target configurations in the same workspace.支持在同一个工作区中构建多个目标配置。
Doesn’t collide with any other tools.
Is easy to access.
Is easy to clean, even selectively.
Is unambiguous, even if the user relies on symbolic links when changing into their client directory.是明确的，即使用户在切换到其客户端目录时依赖符号链接。
All the build state per user should be underneath one directory (“I’d like to clean all the .o files from all my clients.”)
每个用户的所有构建状态都应位于一个目录下（“我想清除所有客户端的所有 .o 文件。”）

Current layout

当前实施的解决方案：

• 包含repo 边界文件的目录

  • 必须从包含 repo 边界文件的目录或其子目录调用 Bazel。换句话说，必须从存储库内部调用 Bazel。否则，会报告错误。

• outputRoot 目录

  • 在 Linux 上 默认为 ${XDG_CACHE_HOME}/bazel（如果未设置 XDG_CACHE_HOME 环境变量，则为 ~/.cache/bazel），
  • 在 macOS 上为 /private/var/tmp
    /private/var/tmp

• outputUserRoot 目录

  • Bazel 用户的构建状态位于 outputRoot/_bazel_$USER 下方。这称为 outputUserRoot 目录。
    /private/var/tmp/_bazel_jack/

• installBase 目录

  • outputUserRoot 目录下有一个 install 目录，其中有一个 installBase 目录，其名称是 Bazel 安装清单的 MD5 哈希值。/private/var/tmp/_bazel_jack/install/407b1ab4400596af2aee426156d1f82d

• outputBase 目录

  • 在 outputUserRoot 目录下，还会创建一个 outputBase 目录，其名称是工作区根目录路径名的 MD5 哈希值。因此，例如，如果 Bazel 在工作区根目录 /home/user/src/my-project（或在与该目录符号链接的目录中）中运行，则会创建一个名为：/home/user/.cache/bazel/_bazel_user/d41a31ac2e17db9f7c57cb77e1261555 的输出基目录。您还可以在工作区根目录中运行 echo -n $(pwd) | md5sum 来获取 MD5。
    /private/var/tmp/_bazel_jack/d41a31ac2e17db9f7c57cb77e1261555

  • 您可以使用 Bazel 的 --output_base 启动选项覆盖默认的输出基目录。例如，bazel --output_base=/tmp/bazel/output build x/y:z。

• the default install base and output base directories

  • 您还可以使用 Bazel 的 --output_user_root 启动选项来覆盖默认安装基目录和输出基目录 install base and output base directories。例如：bazel --output_user_root=/tmp/bazel build x/y:z。

The symlinks for “bazel-”, “bazel-out”, “bazel-testlogs”, and “bazel-bin” are put in the workspace directory; these symlinks point to some directories inside a target-specific directory inside the output directory. (Output Directory Layout)These symlinks are only for the user’s convenience, as Bazel itself does not use them. Also, this is done only if the workspace root is writable.“bazel-”、“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中特定于目标的目录中的某些目录。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，只有当工作区根目录可写时才会这样做。

Layout diagram

The directories are laid out as follows:目录布局如下：

<workspace-name>/                         <== The workspace root
  bazel-my-project => <..._main>          <== Symlink to execRoot
  bazel-out => <...bazel-out>             <== 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)包含首次运行时从 bazel 可执行文件的数据部分解压的二进制文件和脚本（例如辅助脚本和主 Java 文件 BazelServer_deploy.jar）
    7ffd56a6e4cb724ea575aba15733d113/     <== Hash of the client's workspace root (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.操作缓存目录层次结构,这包含 FilesystemValueChecker 使用的文件元数据（时间戳，可能最终还有 MD5总和持久记录。
      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.远程存储库下载/符号链接到的目录。
      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.所有操作的工作目录。对于沙盒和远程执行等特殊情况，操作将在模拟 execroot 的目录中运行。
                                              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.
        _main/                            <== Working tree for the Bazel build & root of symlink forest: execRootBazel ,构建的工作树和符号链接林的根：execRoot
          _bin/                           <== Helper tools are linked from or copied to here.

          bazel-out/                      <== All actual output of the build is under here: outputPath
            _tmp/actions/                 <== Action output directory. This contains a file with the
                                              stdout/stderr for every action from the most recent
                                              bazel run that produced output.
            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. ,//foo/bar:baz 可执行文件的运行文件符号链接场。
                  MANIFEST
                  _main/
                    ...
              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
       

https://bazel.build/rules/lib/builtins/runfiles
A container of information regarding a set of files required at runtime execution. This object should be passed via DefaultInfo in order to tell the build system about the runfiles needed by the outputs produced by the rule.
运行时执行所需的一组文件信息的容器。此对象应通过DefaultInfo传递，以便告知构建系统规则生成的输出所需的运行文件。

bazel clean

bazel clean does an rm -rf on the outputPath and the action_cache directory. It also removes the workspace symlinks. The --expunge option will clean the entire outputBase.