Thread: How to Share Variable Value from one source file to other isuing Header File

You cannot have two main functions in the same program. Are you trying to share values between two different programs? If so, perhaps writing to a file would be an appropriate approach.

Originally Posted by SimplySud

Now I am struck. How to to compile? I link all these file.
I used following method:

Code:

  gcc Sender.c  -o Sender Sender.h 
gcc Receiver.c -o Receiver Student.h

That's the wrong method. Header files do not need to be specified on the compiler's command line.

That aside, those two commands will produce two distinct executables.

Originally Posted by SimplySud

Than I run Sender and after that Receiver.I per my knowledge, Receiver should give difference but it gives error :

Code:

  Receiver.c: In function ‘main’:
Receiver.c:10:42: error: ‘Send’ undeclared (first use in this function)
  printf(" Total Receive is %d\n",Receive-Send);

Sorry, but I don't believe you.

Firstly, that error message is not what you would get if you ran the programs. It is a compilation error which would prevent the executables being built.

Second, given the code you showed for Receiver.c and Sender.h, the compiler would not give that error message either.

That leads me to suspect the code you posted in the forum differs from the code you are working with. Modifying the Receiver.c (as you have shown it here) to remove the "#include "Sender.h"" preprocessor directive would result in that error.



More generally, extern variables (at file scope) allow sharing static variables between functions within a single executable. They do not provide a means of sharing variables between different executables.

As laserlight said, a program can only have one main() function. If you attempt to build a program with two main() functions then the linker will refuse to build your program, and probably complain about duplication.

Lastly, main() returns int. Not void.