I am trying to write one regexp to match C preprocessor commands in C program. I wonder if you can give me some suggestions?
Thank you so much in advance.
3 Answers
That would be
grep '^[[:blank:]]*#'
Note that this will only grep the first line of a multi line preprocessor directive (continued with backslash newline).
2 Comments
Potatoswatter
Overall wisdom notwithstanding, I approve this answer and I wrote a preprocessor. The entire requirements for a directive are that it goes from a
# or %: token following a newline, to just before the next newline. Whether the inside of the directive is well-formed is another matter. The other shortcoming of this approach is that it doesn't allow a comment before the #, but seriously who cares.
David Dai
@Jens Thank you Jens. I will have a try later.
May be this: (not too exact though)
\s*#\s*(define|error|import|undef|elif|if|include|using|else|ifdef|line|endif|ifndef|pragma)\s*\S*
You can use cpp and pass the option -dM to list out all defined macros.
cpp -dM test.c
3 Comments
Antti Haapala
can have space after #
Jens
That's not working. Some directives don't need anything to follow, and there's even the empty directive just consisting of '#'. Then, #import and #using are not C directives.
David Dai
@AnttiHaapala Thank you for your reply. I will have a try.
This regex illustrates how the backslash \ newline can be integrated using recursive regex:
#(?<line>[^#].*?(\n|(\\[^\n]*\n(?&line))))
Hope this helps.
Comments
awk. This didn't change recently.