difference between bazel-bin and bazel-out

In Bazel, the bazel-bin and bazel-out directories serve distinct purposes in the build process, each playing a critical role in managing and organizing build artifacts. Here’s a detailed explanation of the differences between these directories:

1. bazel-bin

Purpose:

• The bazel-bin directory is where Bazel stores the final output artifacts of the build process. These artifacts are the result of build actions such as compiled binaries, libraries, and other generated files that are ready for use.

Characteristics:

• Final Outputs: Contains the final, built artifacts that are intended for use or deployment.
• Symlinks: Often contains symlinks to files in the bazel-out directory. These symlinks provide a convenient path for users to access the build outputs.
• Organized by Targets: The directory structure within bazel-bin reflects the structure of the targets defined in the BUILD files.

Example Contents:

• If you build a target //src:my_app, the resulting executable or binary would be found in bazel-bin/src/my_app.

2. bazel-out

Purpose:

• The bazel-out directory is where Bazel stores all intermediate and final build outputs. This includes not only the final artifacts but also temporary files and intermediate outputs generated during the build process.

Characteristics:

• Intermediate and Final Outputs: Contains both intermediate files used in the build process and the final output artifacts.
• Configuration-specific Directories: Organized by build configurations, such as fastbuild, opt, or dbg. Each configuration has its own subdirectory within bazel-out.
• Sandboxed Environment: Helps manage and isolate build environments to ensure reproducibility and minimize external influences on the build.

Example Contents:

• If you build with the default configuration, you might see paths like bazel-out/k8-fastbuild/bin/src/my_app.

Detailed Comparison:

1. Purpose and Content:

• bazel-bin: Primarily holds the final, user-facing build artifacts.
• bazel-out: Contains all build-related files, including intermediate files, final artifacts, and configuration-specific directories.

2. Directory Structure:

• bazel-bin: Simplified structure with symlinks to final outputs, organized by the target paths.
• bazel-out: More complex structure reflecting the entire build process, including subdirectories for different build configurations.

3. User Interaction:

• bazel-bin: Users typically interact with this directory to access the final build artifacts.
• bazel-out: Used internally by Bazel during the build process; users generally do not need to interact directly with this directory.