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


bear [options] -- [build command]


The JSON compilation database <> is used in Clang project to provide information how a single compilation unit was processed. When that is available then it is easy to re-run the compilation with different programs.

Bear executes the original build command and intercept the command executions issued by the build tool. From the log of command executions it tries to identify the compiler calls and creates the final compilation database.


Print version number.
Print help message.
Enable verbose logging.
Specify output file. (Default file name provided.) The output is a JSON compilation database.
Use previously generated output file and append the new entries to it. This way you can run Bear continuously during work, and it keeps the compilation database up to date. File deletion and addition are both considered. But build process change (compiler flags change) might cause duplicate entries.
Specify a configuration file. The configuration file captures how the output should be formatted and which entries it shall contain.
Force to use the dynamic linker method of intercept command.
Force to use the compiler wrapper method of intercept command.


Intercepts events that happened during the execution of the build command.
Deduce the semantics of the commands captured by bear-intercept(1).


The JSON compilation database definition changed over time. The current version of Bear generates entries where:

has absolute path.
has absolute path.
has absolute path.
used instead of command to avoid shell escaping problems. (Configuration can force to emit the command field.) The compiler as the first argument has absolute path. Some non compilation related flags are filtered out from the final output.


Read bear-citnames(1) man page for the content of this file. bear is not reading the content of this file, but passing the file name to bear citnames command.


The exit status of the program is the exit status of the build command. Except when the program itself crashes, then it sets to non-zero.


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

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 (read bear-intercept(1) man page), it needs to run the configure step with Bear too (and discard that output), before run the build with Bear.

There could be many reasons for any of these failures. It’s better to consult with the project wiki page for known problems, before open a bug report.


Copyright (C) 2012-2023 by László Nagy <>


László Nagy.

January 2, 2023 Bear User Manuals