clang-format

Format a file and print the result to stdout

$ clang-format [path/to/file]

$ clang-format -i [path/to/file]

$ clang-format --style [LLVM|GNU|Google|Chromium|Microsoft|Mozilla|WebKit] [path/to/file]

$ clang-format --style=file [path/to/file]

$ clang-format --style [LLVM|GNU|Google|Chromium|Microsoft|Mozilla|WebKit] --dump-config > [.clang-format]

clang-format [options] [files...] | code

-assume-filename=string
    Filename for style lookup when reading stdin

-clear-filter-cache
    Clear style filter cache

-cursor=file:line:column
    Cursor position for editor integration

-dump-config
    Dump config options to stdout

-fallback-style={llvm|google|...}
    Default style if file lookup fails

-F filename
    Output file with XML replacements

-help
    Show help

-i
    Edit files in place (stdin if no files)

-length=N
    Format range of N columns with -offset

-lines=file1:line1-line2,file2:...
    Format specific line ranges

-offset=N
    Start range formatting at offset N

-output-replacements-xml
    Output XML replacements to stdout

-sort-includes
    Sort #include directives

-style={llvm|file|...}
    Specify coding style

-v
    Verbose mode

clang-format is a powerful tool from the LLVM/Clang project designed to automatically format C, C++, Objective-C, Java, JavaScript, and Protobuf code according to predefined style rules. It enforces consistent coding styles across teams, reducing debates over formatting and improving readability.

It reads configuration from a .clang-format YAML file, which can be placed in the project root, user home, or specified via options. Popular built-in styles include LLVM, Google, Chromium, Mozilla, and WebKit. Custom styles allow fine-grained control over indentation, line length, brace placement, and more.

Usage is straightforward: pipe code through stdin for quick formatting, or apply to files with -i for in-place edits. It integrates seamlessly with IDEs like VS Code, Vim, and Emacs via plugins, enabling on-save formatting. Advanced features include XML replacement output for editor integration, range formatting, and include sorting.

Ideal for large codebases, it processes files rapidly and supports dry runs. While highly configurable, it may require tuning for non-standard codebases. Widely used in open-source projects like LLVM itself.

Primarily for C-family languages; JavaScript/Protobuf support limited. Complex configs may need YAML expertise. No semantic understanding—purely syntactic formatting.

Create .clang-format with clang-format -dump-config > .clang-format, then edit YAML keys like IndentWidth: 4, ColumnLimit: 80.

clang-format -i *.cpp formats all .cpp files in place.
cat file.cpp | clang-format formats stdin.

Introduced in LLVM 3.3 (2013) as part of Clang toolchain. Evolved rapidly with community contributions; major enhancements in LLVM 10+ for new styles and performance. Now standard in most C++ projects for CI/CD integration.

clang(1), clang-tidy(1), astyle(1)