如何在Makefile中输入父目录? [英] How to enter a parent directory in Makefile?

问题描述

我有以下Makefile(GNU Make 3.81):

I've got the following Makefile (GNU Make 3.81):

CWD:=$(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))

all:
        pwd
        cd "$(CWD)/.."
        pwd
        cd ".."
        pwd

以下是输出:

$ make
pwd
/Users/kenorb/temp/foo
cd "/Users/kenorb/temp/foo/.."
pwd
/Users/kenorb/temp/foo
cd ".."
pwd
/Users/kenorb/temp/foo

似乎cd通过..进入父目录没有任何作用.

It seems that cd'ing to parent directory via .. doesn't take any effect.

如何相对于Makefile文件将当前工作目录更改为父目录?

How do I change the current working directory to a parent directory relatively to Makefile file?

推荐答案

此问题与以下事实有关:规则配方的每一行都在专用的shell实例(即新进程)中执行.因此，在一行中运行cd不会对另一行中的命令产生任何影响，因为这些命令是由不同的进程执行的.

This issue has to do with the fact that each line of a rule's recipe is executed in a dedicated shell instance (i.e.: a new process). So, running cd in one line, won't have any effect for a command in another line, because these commands are executed by different processes.

您可以使用 .ONESHELL (GNU Make 3.82或更高版本)可在单个相同的shell实例中运行所有配方行:

You can either use .ONESHELL (GNU Make 3.82 or later) to run all the recipe's lines in a single and the same shell instance:

CWD:=$(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))

.ONESHELL:
all:
        pwd
        cd "$(CWD)/.."
        pwd
        cd ".."
        pwd

或仅将所有命令放在一行中:

or just keep all the commands in a single line:

CWD:=$(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))

all:
        pwd; cd "$(CWD)/.."; pwd; cd ".."; pwd

更改工作目录仅在该食谱内部生效.

The change of the working directory takes effect only inside that recipe.

请注意，无法为调用make的shell更改makefile中的当前工作目录，因为这是一个process'属性，并且正在运行的make实例将执行cd是另一个(子)过程.因此，它只会更改该子进程的工作目录.

Note that changing the current working directory inside the makefile for the shell that invoked make is not possible, since that's a process' property, and the running make instance that will execute cd is another (sub)process. Therefore, it will only change the working directory of that subprocess.

这是您不能通过执行脚本而没有 sourcing 来更改Shell工作目录的相同原因:因为脚本在新的Shell实例(即子进程)中运行.

That is the same reason you cannot change the working directory of a shell by executing a script without sourcing it: because the script runs in a new shell instance (i.e.: a subprocess).

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