How do I specify a clang-format file?

I just built clang 5.0.0 on a Redhat 6 machine and tried to run clang-format. I'm unable to get the -style option to read in a style file. Here's an example of a set of commands that I think should work:

./clang-format -style=llvm -dump-config > .llvm-format
./clang-format -style=.llvm-format ~/myFile.cc

When I run this command I get the following error:

Invalid value for -style

It appears to find and use .clang-format when placed in a parent directory as expect. The built-in types also work:

./clang-format -style=Mozilla ~/myFile.cc

The problem, then, is that I can't specify explicitly a .clang-format file to use. Is this a problem with my build or am I misusing clang-format oir misunderstanding the documentation?

I got confused by that too. When they tell you to use the flag -style=file they literally mean for you to type out -style=file, NOT -style=<path/to/actual/filename>.

With this flag, clang-format will look for a file called .clang-format in the directory of the target file. If it doesn't find any it will cd .. and try again. There doesn't seem to be a way to tell clang-format to use a file that is not named exactly .clang-format.

The correct usage for your example would be:

./clang-format -style=llvm -dump-config > ~/.clang-format
./clang-format -style=file ~/myFile.cc

(updated 2022-02-25) clang 14.0.0-RC1 or later now supports -style=file:<format_file_path> after this change "Add option to explicitly specify a config file" entered the main branch. It's documented here. This worked for me:

.\LLVM14.0.0RC1\bin\clang-format.exe test.cpp -style=file:my_clang_format.txt

Just an additional hint: (in my case on Windows 10) - if you dump the config to a file, check the ascii coding afterwards, e.g. in Notepad++ - the .clang-format file has to be utf8 without BOM !!! (you can convert it in Notepadd++) - otherwise you get an error like "YAML:1:4: error: Got empty plain scalar" - place the .clang-format file in the same folder or in a parent directory of the code-file.c

A correct command line call to format the code-file.c would look like that: clang-format.exe -style=file -i C:\path\code-file.c