通过 CMake 运行 bash 命令
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Running a bash command via CMake
提问by assignment_operator
I'm trying to have CMake either run three bash commands or a bash script. However, I can't seem to get it to work.
我试图让 CMake 运行三个 bash 命令或一个 bash 脚本。但是，我似乎无法让它发挥作用。
The bash commands are:
bash 命令是：
cd ${CMAKE_SOURCE_DIR}/dependencies/library
make
cd ${CMAKE_BINARY_DIR}
Essentially, I would like CMake to build the library in that directory if it does not already exist.
本质上，如果库不存在，我希望 CMake 在该目录中构建库。
Here's the CMake code I tried:
这是我尝试过的 CMake 代码：
if(NOT "${CMAKE_SOURCE_DIR}/dependencies/library/lib.o")
execute_process(COMMAND cd ${CMAKE_SOURCE_DIR}/dependencies/library)
execute_process(COMMAND make)
execute_process(COMMAND cd ${CMAKE_BINARY_DIR})
endif(NOT "${CMAKE_SOURCE_DIR}/dependencies/library/lib.o")
However, it's not building anything. What am I doing wrong?
但是，它并没有构建任何东西。我究竟做错了什么？
Also, while I'm here asking this: should the third command, to move to the binary folder, be included?
另外，虽然我在这里问这个问题：是否应该包括第三个命令，移动到二进制文件夹？
Thanks!
谢谢！
回答by Phil Be
execute_process()is executed during configure time. But you want this to run at build time, thus add_custom_command()and add_custom_target()is what you're looking for.
execute_process()在配置期间执行。但你希望在构建时运行，因此add_custom_command()和add_custom_target()是你在找什么。
In this special case you want to generate an output file, so you should go for add_custom_command()(both are essentially the same, but commandproduces one or multiple output files, while targetdoes not.
在这种特殊情况下，您想要生成一个输出文件，因此您应该选择add_custom_command()（两者本质上相同，但command会生成一个或多个输出文件，而target不会。
The cmake snippet for this should look something like the following:
用于此的 cmake 代码段应如下所示：
add_custom_command(
OUTPUT ${CMAKE_SOURCE_DIR}/dependencies/library/lib.o
WORKING_DIR ${CMAKE_SOURCE_DIR}/dependencies/library
COMMAND make
)
You then have to add the output file in another target as dependency, and everything should (hopefully) work as expected.
然后，您必须将输出文件添加到另一个目标中作为依赖项，并且一切都应该（希望）按预期工作。
You can also add DEPENDSstatements to the add_custom_command()call to rebuild the object file in case some input sources have changed.
如果某些输入源发生更改，您还可以DEPENDS向add_custom_command()调用添加语句以重建目标文件。
