[CMake] CMake string REGEX REPLACE and environment variables

[Nils Gladitz]

On 10/20/2015 01:49 PM, Oleg Trenkin wrote:
> Hi all,
>
> Does anybody know why I can't evaluate environment variable inside
> "REGEX REPLACE"?
>
> Example,
> I have a value:
> set(value "LD_LIBRARY_PATH=my_path:$LD_LIBRARY_PATH")
>
> I expect:
> value = "LD_LIBRARY_PATH=my_path:some_system_path_from_env"
>
> What I'm doing:
> string(REGEX REPLACE "\\$\\{([a-zA-Z0-9_]+)\\}" "$ENV{\\1}" value ${value})
>
> Regexp works,
> CMAKE_MATCH_1  and \\1 both have "LD_LIBRARY_PATH" string
>
> string(REGEX REPLACE "\\$\\{([a-zA-Z0-9_]+)\\}" "\\1" value ${value})
> will return "LD_LIBRARY_PATH=my_path:LD_LIBRARY_PATH"
> but why can't I use $ENV{\\1}, or maybe I'm doing something wrong?

$ENV{} is evaluated before string() gets called so \\1 is evaluated as 
the literal name of the variable.


This works for me somewhat:

   set(value "LD_LIBRARY_PATH=my_path:$LD_LIBRARY_PATH")

   string(REGEX MATCHALL "\\$[a-zA-Z0-9_]+" MY_MATCHES "${value}")

   foreach(MATCH ${MY_MATCHES})
       string(SUBSTRING "${MATCH}" 1 -1 MY_NAME)

       string(REPLACE "${MATCH}" "$ENV{${MY_NAME}}" value "${value}")
   endforeach()

   message("${value}")


Nils