% BEAR(1) Bear User Manuals % László Nagy % April 27, 2026

NAME

Bear - a tool to generate compilation database for Clang tooling.

SYNOPSIS

bear [OPTIONS] [--] [BUILD_COMMAND...]

bear intercept [OPTIONS] [--] BUILD_COMMAND...

bear semantic [OPTIONS]

DESCRIPTION

Bear is a tool that generates a JSON compilation database for Clang tooling by intercepting command executions during the build process. The JSON compilation database is used in the Clang project to provide information about how individual compilation units were processed, enabling tools like clang-tidy, clangd, and other Clang-based analysis tools to understand your project's build configuration.

Bear operates by intercepting system calls during the build process to capture compilation commands. It supports two main interception methods: dynamic library preloading (on Unix-like systems) and wrapper executables (cross-platform). The captured commands are then filtered through semantic analysis to identify actual compiler invocations and generate the final compilation database.

Bear can operate in three modes:

• Combined mode (default): Runs both interception and semantic analysis in sequence
• Intercept mode: Only captures build events to an intermediate file
• Semantic mode: Processes previously captured events to generate the compilation database

OPTIONS

-c, --config FILE : Specify a configuration file path. The configuration file controls output formatting, compiler recognition, source filtering, and duplicate handling.

-o, --output FILE : Specify the output file path (default: compile_commands.json). The output is a JSON compilation database.

-a, --append : Append results to an existing output file instead of overwriting it. This allows incremental updates to the compilation database.

-h, --help : Print help information.

-V, --version : Print version information.

COMMANDS

Calling bear without commands will execute the combined mode, and will intercept the compiler calls and generate a compilation database as output.

bear intercept

Intercepts command execution events during the build process and saves them to an events file for later processing.

bear intercept [OPTIONS] [--] BUILD_COMMAND...

bear semantic

Processes previously captured events to generate a compilation database through semantic analysis.

bear semantic [OPTIONS]

OUTPUT

Bear generates a JSON compilation database conforming to the Clang JSON Compilation Database specification. The output is a JSON array of compilation entry objects.

Entry Format

Each compilation database entry contains the following fields:

directory : The working directory of the compilation (absolute path)

file : The main translation unit source file (absolute path)

arguments : The compilation command as an array of strings (preferred format)

command : The compilation command as a single shell-escaped string (alternative to arguments)

output : The output file produced by compilation (optional, absolute path)

Output Formatting

The output format can be controlled through the configuration file:

• Path resolution: Paths can be formatted as absolute, relative, canonical, or as-is
• Entry format: Choose between arguments array (preferred) or command string
• Field inclusion: Control whether the output field is included
• Source filtering: Include/exclude files based on directory rules
• Duplicate filtering: Remove duplicate entries based on configurable field matching

Bear generates entries where all paths are absolute by default, and uses the arguments field instead of command to avoid shell escaping issues.

CONFIG FILE

Bear uses a YAML configuration file to control its behavior. The configuration file follows a structured schema with several main sections.

Configuration Schema

schema: "4.1"
intercept:
  mode: wrapper
compilers:
  - path: /usr/bin/cc
    as: gcc
  - path: /usr/local/bin/gcc
    ignore: true
sources:
  directories:
    - path: /project/tests
      action: exclude
duplicates:
  match_on:
    - file
    - arguments
format:
  paths:
    directory: canonical
    file: canonical
  entries:
    use_array_format: true
    include_output_field: true

This example configuration file: sets the interception mode to wrapper, hints the /usr/bin/cc to be the main compiler in this project, which is the GNU compiler, hints to ignore the /usr/local/bin/gcc compilers from the project, instructs to ignore files from /project/tests, instructs to detect duplicates based on the file and arguments fields of the output file, instructs to format the output to use canonical path for the file and directory fields of the output file, instructs to use the arguments over the command field in the output file, instructs to include the output field in the output file.

Configuration Sections

The configuration file uses schema version 4.1 and has the following structure:

intercept

Controls the command interception method:

• mode: preload (Unix) or wrapper (cross-platform)

compilers

Contains hints about what compiler needs to be recognized and what that compiler is.

• path: Path to the compiler executable
• as: Compiler type hint for semantic analysis. Valid values are: gcc, clang, flang, intel-fortran, cray-fortran, cuda, msvc, clang-cl, intel_cc, nvidia-hpc, armclang, ibm_xl.
• ignore: Whether to ignore this compiler.

The generic compiler names cc and c++ default to GCC semantics. On platforms where these map to a different compiler (macOS, FreeBSD, OpenBSD), use the as field to override:

compilers:
  - path: /usr/bin/cc
    as: clang
  - path: /usr/bin/c++
    as: clang

sources

Filtering functionality based on the source file location.

• directories: List of directory-based inclusion/exclusion rules

Directory rules are evaluated in order, with the last matching rule determining inclusion/exclusion. Empty directories list means include everything.

duplicates

Filtering functionality based on duplicate detection. Here you can define which fields of the output file should be used in the duplicate detection.

• match_on: List of fields to use for duplicate detection (file, arguments, directory, command, output)

format

Output formatting configuration:

• paths.directory and paths.file: How to format paths of these fields. The allowed values are:
  • as-is: No transformation,
  • canonical: Resolve to canonical path,
  • relative: Make relative to directory field,
  • absolute: Convert to absolute path,
• entries.use_array_format: Use arguments array instead of command string
• entries.include_output_field: Include output field in entries

Default Configuration

If no configuration file is specified, Bear uses built-in defaults optimized for most use cases.

ENVIRONMENT

RUST_LOG : Controls the logging level for Bear's internal operations. This environment variable is essential for troubleshooting and debugging Bear's behavior.

Supported log levels (in order of verbosity):

- `error` - Only show critical errors
- `warn` - Show warnings and errors  
- `info` - Show informational messages, warnings, and errors
- `debug` - Show detailed debugging information

Examples:
```
RUST_LOG=debug bear -- make all
RUST_LOG=info bear intercept -- cmake --build .
```

FILES

The configuration file bear.yml is searched in the following locations, in order:

./bear.yml : The current working directory.

$XDG_CONFIG_HOME/bear.yml, $XDG_CONFIG_HOME/Bear/bear.yml (Unix) : When $XDG_CONFIG_HOME is set.

$HOME/.config/bear.yml, $HOME/.config/Bear/bear.yml (Unix) : When $XDG_CONFIG_HOME is unset.

%LOCALAPPDATA%\bear.yml, %LOCALAPPDATA%\Bear\bear.yml (Windows) : When %LOCALAPPDATA% is set.

%APPDATA%\bear.yml, %APPDATA%\Bear\bear.yml (Windows) : When %APPDATA% is set.

The first file found is loaded; remaining locations are not consulted.

EXIT STATUS

Bear returns the exit status of the executed build command when running in combined or intercept mode. When the build command succeeds, Bear returns 0. When the build command fails, Bear returns the same non-zero exit code.

In semantic mode, Bear returns 0 on success and a non-zero exit code if semantic analysis fails.

If Bear itself encounters an internal error or crashes, it returns a non-zero exit code regardless of the build command's status.

TROUBLESHOOTING

The potential problems you can face with are: the build with and without Bear behaves differently or the output is empty.

Debug Logging

Before reporting any issues, always run Bear with debug logging enabled:

RUST_LOG=debug bear -- your-build-command

This will provide detailed information about Bear's internal operations. And the debug output is essential for diagnosing problems and must be included in any bug reports.

Common Issues

The most common cause for empty outputs is that the build command did not execute any commands. The reason for that could be, because incremental builds not running the compilers if everything is up-to-date. Remember, Bear does not understand the build file (eg.: makefile), but intercepts the executed commands.

The other common cause for empty output is that the build has a "configure" step, which captures the compiler to build the project. In case of Bear is using the wrapper mode, it needs to run the configure step with Bear too (and discard that output), before run the build with Bear.

Compiler Env Vars With Flags

In wrapper mode, Bear accepts compiler environment variables that carry a trailing flag or two, matching the GNU Make convention:

CC="gcc -std=c11" make
CXX="clang++ -stdlib=libc++" make
CC="/usr/local/bin/gcc -m32" make

Bear splits the value on whitespace, resolves the first token as the compiler, and rewrites the variable so the build still sees the flags (CC=<wrapper_path> -std=c11).

This convention is a Unix / GNU Make inheritance; it applies when bear -- make runs under sh/bash (including MSYS2, Git Bash, WSL on Windows), not under native Windows build systems (MSBuild, nmake, cmd, PowerShell), which do not consume CC/CXX from the environment.

For anything beyond simple whitespace-separated tokens (flags containing spaces, shell quoting, metacharacters, command substitutions), use CFLAGS, CXXFLAGS, or LDFLAGS instead of packing it into CC. Those variables are the portable channel for compilation flags and every build system expects them. Bear does not parse or rewrite them; they reach the compiler untouched.

Getting Help

There could be many reasons for any of these failures. When seeking help:

1. Always include debug logs (RUST_LOG=debug) in your report
2. Consult the project wiki page for known problems
3. Search existing issues before opening a new bug report
4. Follow the bug report template, provide the requested fields

COPYRIGHT

Copyright (C) 2012-2026 by László Nagy https://github.com/rizsotto/Bear