bash $(shell pwd) 给出什么值？
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What value does $(shell pwd) give?
提问by Shorn Jacob
Going through a MakeFile I find
通过我发现的 MakeFile
PROJECT_ROOT = $(shell pwd)
PROJECT_ROOT = $(shell pwd)
What value does it give?
它赋予什么价值？
$SHELLgives the shell and $PWDgives present working directory
But what does $(shell pwd) give?
$SHELL给出 shell 并$PWD给出当前的工作目录 但是 $(shell pwd) 给出了什么？
回答by Austin Phillips
The $(shell)function calls out to the shell to execute a command. The command being executed in this case is pwd, like if you ran pwdat the bash shell prompt.
该$(shell)函数调用外壳程序以执行命令。在这种情况下执行的命令是pwd，就像您pwd在 bash shell 提示符下运行一样。
So, $(shell pwd)will return the current working directory. You may not be guaranteed that the $PWDvariable exists in your make environment.
因此，$(shell pwd)将返回当前工作目录。您可能无法保证该$PWD变量存在于您的 make 环境中。
