How do I make my own header file in C?

问题

I tried to make my own header file but it doesn't work vim says

wget.h:2:2: error: invalid preprocessing directive #ifndef__WGET_H__
wget.h:3:2: error: invalid preprocessing directive #define__WGET_H__
wget.h:7:2: error: #endif without #if

My code is this:

//wget header file
#ifndef__WGET_H__
#define__WGET_H__

int my_wget (char web_address[]);

#endif /*__WGET_H__*/

it seems fine to me (the examples I have read are much alike with mine) and I don't know what went wrong. Any ideas?

回答1:

Everything is right , just the space was missing.

#ifndef __WGET_H__
#define __WGET_H__

int my_wget (char web_address[]);

#endif __WGET_H__

You would generally use the above , in header files , because , in your project , if you happen(by accident) to include the same header multiple times , then writing the header like this will make sure , that it includes the header only once.

回答2:

You must leave a space between the preprocessor keyword and the label:

#ifndef __WGET_H__
#define __WGET_H__

回答3:

Change:

#ifndef__WGET_H__
#define__WGET_H__

to

#ifndef __WGET_H__
#define __WGET_H__

(note the space between #ifndef and __WGET_H__)

回答4:

You need to leave a space between a preprocessor keyword (e.g. #define) and the label (i.e. __WGET_H__). In other words:

#ifndef __WGET_H__
#define __WGET_H__

will work.

来源：https://stackoverflow.com/questions/15352253/how-do-i-make-my-own-header-file-in-c