2.3.3.2 Showing C Function Headings

To show in which functions differences occur for C and similar languages, you can use the `-p' or `--show-c-function' option. This option automatically defaults to the context output format (see section 2.3.1 Context Format), with the default number of lines of context. You can override that number with `-C lines' elsewhere in the command line. You can override both the format and the number with `-U lines' elsewhere in the command line.

The `-p' and `--show-c-function' options are equivalent to `-F '^[[:alpha:]$_]'' if the unified format is specified, otherwise `-c -F '^[[:alpha:]$_]'' (see section 2.3.3.1 Showing Lines That Match Regular Expressions). GNU diff provides them for the sake of convenience.