如何将命令的输出分配给Makefile变量 [英] How to assign the output of a command to a Makefile variable

问题描述

仅当安装的Python大于某个版本(例如2.5)时，我才需要有条件地执行一些make规则.

I need to execute some make rules conditionally, only if the Python installed is greater than a certain version (say 2.5).

我认为我可以做一些类似的事情:

I thought I could do something like executing:

python -c 'import sys; print int(sys.version_info >= (2,5))'

，然后在ifeq make语句中使用输出(如果可以，则为'1'，否则为'0').

and then using the output ('1' if ok, '0' otherwise) in a ifeq make statement.

在一个简单的bash shell脚本中，它只是:

In a simple bash shell script it's just:

MY_VAR=`python -c 'import sys; print int(sys.version_info >= (2,5))'`

但是在Makefile中不起作用.

but that doesn't work in a Makefile.

有什么建议吗?我可以使用任何其他明智的解决方法来实现这一目标.

Any suggestions? I could use any other sensible workaround to achieve this.

推荐答案

像在MY_VAR=$(shell echo whatever)

me@Zack:~$make
MY_VAR IS whatever

me@Zack:~$ cat Makefile 
MY_VAR := $(shell echo whatever)

all:
    @echo MY_VAR IS $(MY_VAR)

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