including header files

[radha7687]

hello friends,

This is Radha. I have a querry about one of the concepts of c++ like includeing header files in c/c++ program . When i try to inlclude header files for for implementing a program on message queue..

In that when i try to include one of the header files called "SYS\TYPES.H"
it is showing error like "UNABLE TO INCLUDE SYS\TYPES.H" but it is showing that header file in list and even it is present in the directory in the path which i have gave in the directory settings..

please any one help me out to on this as soon as possible please please please.........


Regards,
Radha.

[Laharl]

You've got the wrong slash. Use / instead of \.

[weaknessforcats]

Your compiler's preprocessor looks for header files based on pre-defined paths.

When you #include <aheader.h>, the path t this header must be already defined. Your compiler's documentation will tell how to set this path. Typically, you cn have many paths set and each will be searched for the header.

When you #include "aheader.h", the header is presumed to be in the present working directory (PWD) and if not there, the search reverts the #include <aheader.h>.

I would not use relative paths

[Laharl]

<sys/types> is a Unix header that contains gcc's POSIX types. While it is a relative filepath, the <> notation under Linux goes to /usr/include (or the equivalent, depending on distro) and this file is /usr/include/sys/types.h, so the relative path is necessary by the default gcc/g++ settings, anyway.

[weaknessforcats]

I see. Obviously, my Windows are showing again.

[Banfa]

Actually in general a path like

#include <sys\types.h>

will work by adding the relative path to the each path in the defined set of include paths to search, it is not uncommon on any platform to have a sys include directory from the normal platform include directory that contains platform system headers, while the platform directory contains the C and/or C++ standard library headers (and other junk sometimes (take a look at the Windows include directory)).

e.g.

C:\MyPlatform\include <-- standard library headers here
C:\MyPlatform\include\sys <-- platform system headers here

Even Microsoft follows this a little putting (some of?) the POSIX headers into the sys directory

e.g.

C:\Program Files\Microsoft Visual Studio 8\VC\include\sys\types.h


Normally the sys directory is never explicitly put into the include path and has to be accessed via a relative path.

[weaknessforcats]

Don't forget that with Windows you have to double the backslashes:

C:\\Program Files\\Microsoft Visual Studio 8\\VC\\include\\sys\\types.h
 

[Banfa]

Don't forget that with Windows you have to double the backslashes:

C:\\Program Files\\Microsoft Visual Studio 8\\VC\\include\\sys\\types.h
 

Not in an include statement only in a C type string.