How to reference CMake variable in shell script

Question

I use execute_process to run a shell script,

set(CMAKE_C_FLAGS ...) # here ... means many options
execute_process(
    COMMAND ./my_script.sh)

In my_script.sh I want to use the value of CMAKE_C_FLAGS and how to do it? When echo ${CMAKE_C_FLAGS} in script, I get nothing.

Inside your Make file, you write the value of the variable into a file, and afterwards in your shell script, you read this file. However, in this case I would consider it the other way around: Set the variable in your script before invoking cmake, and pass it to the Makefile. No need of a temporary file then. — user1934428
– user1934428, Commented Dec 14, 2021 at 9:40

Alex Reinking · Accepted Answer · 2021-12-15 00:37:36Z

2

CMake variables are not environment variables.

You can set an environment variable like so:

set(CMAKE_C_FLAGS ...)
set(ENV{CMAKE_C_FLAGS} "${CMAKE_C_FLAGS}")
execute_process(COMMAND "${CMAKE_CURRENT_SOURCE_DIR}/my_script.sh")

Note that this lasts only for the duration of the CMake configure step. This means it will work with execute_process, but not add_custom_command.

Also note that calling a shell script from CMake is a code smell (hinders portability, is weird and probably unnecessary).

answered Dec 15, 2021 at 0:37

Alex Reinking

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2 Comments

Wanghz Over a year ago

So some processing is needed to be done with shell before building the target, what's the correct way to do that if not calling a shell script?

Alex Reinking Over a year ago

"needed to be done with shell" -- this is, let's say, rare.

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