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Many a times we want to conditionally copy some RPGLE script. For this purpose the copybook requires /if, /define, /undefine and /EndIf compiler directives. To use a copybook conditionally we need to follow the following two steps.

Conditionally copy a source code.

1. Surround the script you want to be conditionally copied by the /If Defined xxx and /Endif compiler directives.
2. When you intend to copy this script in your main RPGLE source, surround your /COPY compiler directive by /Define xxx and /Undefine xxx.

That's it. The following example will clarify the things further.

DName+++++++++++ETDsFrom+++To/L+++IDc.Keywords
D W@Var1          S             10P 0 Inz     
 /If Defined(Export)                          
D                                     Export  
 /Else                                        
D                                     Import  
 /EndIf                                       

If you see the error "The keyword is not allowed following keyword EXPORT; keyword is ignored." Please ignore it, because this is just a copybook not a compilable source.

Notice the syntax of the Defined(Export).

Now we will declare the copybook in between definitions of Export.
The following code will Export the variable

.. 1 ...+... 2 ...+.
/Define Export      
/Copy QCPYLESRC,QBC 
/Undefine Export    

And the following code will import the variable

.. 1 ...+... 2 ...+.
/Define Import      
/Copy QCPYLESRC,QBC 
/Undefine Import    

Note: To import the variable it is not required Define import. It's just to clarify the things.

Recommendation: Duplicate definition error is very common when using conditional copybooks, ensure that EVERY LINE OF CODE IS WRITTEN IN SOME CONDITION IN COPYBOOK. Also, avoid using /ELSE directive when using large copybooks or you include copybooks several times in a source code.

That's it with conditional copybook. In the next section we will see some common examples of copybooks.