# Clang Format

### Installation in Ubuntu

```shell
sudo apt install --no-install-recommends clang clang-format
```

### Set up Git Hook

* copy file `git-clang-format` to `/usr/local/bin` 
* copy file `pre-commit` to `.git/hooks` of the repository under development
* generate `.clang-format` file in the root directory of the project

#### File: pre-commit

<pre class="language-python"><code class="lang-python"><strong>#!/usr/bin/env python
</strong>
import sys
import subprocess
output = subprocess.check_output(["git", "clang-format", "--diff"])

if output not in ['no modified files to format\n', 'clang-format did not modify any files\n']:
  sys.exit("""Error: clang format check failed. Run git clang-format -f to fix it, then commit again.
NOTE: if (and *only* if) this is a merge commit, you may skip this check with 'git commit -n'""")
</code></pre>

#### File: git-clang-format

* <https://github.com/hanzheteng/LOCUS/blob/main/scripts/clang_setup/clang/git-clang-format>

#### File: .clang-format

* Example of full configuration: <https://github.com/hanzheteng/LOCUS/blob/main/.clang-format>
* A brief example: <https://github.com/MIT-SPARK/TEASER-plusplus/blob/master/.clang-format>

### Usage

* If git hook is set, run the following command before every git commit.

```shell
git clang-format -f
```

* In addition to being used as a git hook, clang can format a single c++ file in command line.

```shell
clang-format -i -style=google *.cpp  # use google default coding style
clang-format -i -style=file *.cpp  # if .clang-format is ready (in the same dir)
```

* To disable clang formatting in certain cases.

```cpp
int formatted_code;
// clang-format off
    void unformatted_code;
// clang-format on
void formatted_code_again;
```

### References

#### Official documentation

* <https://clang.llvm.org/docs/ClangFormat.html>
* <https://clang.llvm.org/docs/ClangFormatStyleOptions.html>

#### Tutorials

* <https://www.csd.uoc.gr/~hy255/tuts/2021/clang_format_tutorial.pdf>

#### A script to automatically install clang-format and set up git hook

* <https://github.com/hanzheteng/LOCUS/blob/main/scripts/clang_setup/clang_setup.sh>


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