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Full Discussion: Conditional Compilation based on Environmental Variable in Unix
Top Forums Programming Conditional Compilation based on Environmental Variable in Unix Post 302314088 by BrighterLater on Thursday 7th of May 2009 10:52:44 AM
Old 05-07-2009
Conditional Compilation based on Environmental Variable in Unix
I want to be able to access an environment variable to control how a program is compiled.
So:
export MY_VERSN=9

Then ideally, within my C++ code, I would have

#if MY_VERSN = 9
iret = FRED9()
#else
iret = FRED()
#endif

The way I thought I could do it is that in the script that sets up the environmental variable MY_VERSN (which I need in any case) , I could also create an include file fred.h containing

#define MY_VERSN 9

and then include fred.h in my C++ code.

I think that my requirement to conditionally compile based on an env variable must be a common one; so I'd be grateful for sugestions on how it is usually achieved. Thanks
 

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LEARN ABOUT SUNOS

unset

asadmin-unset(1AS)						   User Commands						asadmin-unset(1AS)

NAME

       asadmin-unset, unset - removes one or more variables from the multimode environment

SYNOPSIS

       unset env_var [env_var]*

       Removes	one or more variables you set for the multimode environment. The variables and their associated values will no longer exist in the
       environment.

OPERANDS

       env_var		       environment variable to be removed.

       Example 1: Using unset to remove environment variables

       asadmin> export AS_ADMIN_HOST=bluestar AS_ADMIN_PORT=8000 AS_ADMIN_USER=admin AS_ADMIN_PASSWORD=password
       asadmin> export AS_ADMIN_PREFIX=server1.jms-service
       asadmin> export
       AS_ADMIN_HOST=bluestar
       AS_ADMIN_PORT=8000
       AS_ADMIN_USER=admin
       AS_ADMIN_PASSWORD=********
       AS_ADMIN_PREFIX=server1.jms-service
       asadmin> unset AS_ADMIN_PREFIX
       asadmin> export
       AS_ADMIN_HOST=bluestar
       AS_ADMIN_PORT=8000
       AS_ADMIN_USER=admin
       AS_ADMIN_PASSWORD=********

       Using the export command without the argument lists the environment variables that are set. Notice the AS_ADMIN_PREFIX is not in the  envi-
       ronment after running the unset command.

EXIT STATUS

       0		       command executed successfully

       1		       error in executing the command

       asadmin-export(1AS), asadmin-multimode(1AS)

J2EE 1.4 SDK							    March 2004							asadmin-unset(1AS)
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