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 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 Showing Lines That Match Regular Expressions). GNU diff provides them for the sake of convenience.