[Courses] C Programming For Absolute Beginners, Lesson 1: Setting Up, First Program

[Kathryn Hogg]

On 2012-02-05 18:45, Jacinta Richardson wrote:
> On 06/02/12 10:49, jim wrote:
>>      Note that the #include preprocessor directive seems to take
>> <stdio.h>
>> as an argument.
>>      The<  >  angle bracket characters have a special meaning:
>> /usr/include/
>>
>
> The angle brackets refer to the system directories, which might not
> always be /usr/include but could even be /opt/usr/include etc.

That's not quite correct.  When you have a #include file surrounded by 
angle brackets, it indicates to look for the file according to the 
include path.  The compiler typically has a built in include path but 
you can extended via command line arguments or environment variables:

gcc -I/usr/local/include  will add /usr/local/include to the front of 
the include path.

When you do a #include with double quotes (#include "file.h") that 
means to search the same directory as the file which is doing the 
#include.

For example, if /home/kathryn/src/foo.c  does

#include "foo.h"

then the compiler will search in /home/kathryn/src for foo.h and if it 
doesn't find it, it will search the include path as normal.



-- 
Kathryn Hogg
http://womensfooty.com