diffutils: C Function Headings
2.2.3.2 Showing C Function Headings
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To show in which functions differences occur for C and similar
languages, you can use the '--show-c-function' ('-p') option. This
option automatically defaults to the context output format (⇒
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 '--show-c-function' ('-p') option is equivalent to '-F
'^[[:alpha:]$_]'' if the unified format is specified, otherwise '-c -F
'^[[:alpha:]$_]'' (⇒Specified Headings). GNU 'diff' provides
this option for the sake of convenience.