makefile shell

linyunxian

makefile 里的shell 到底是如何行为的？

1. 
   
2. [~/tmp 0]$ cat make.file
   
3. CC=arm-linux-gcc
   
4. all:
   
5.         echo "$(shell  $(CC)"
   
6. [O_O~/tmp 1]$ make -f make.file
   
7. make: arm-linux-gcc: Command not found
   
8. echo ""
   

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上述的结果很令人疑惑？？？？？怎么解释呢？
做了如下测试：

1. 
   
2. [~/tmp 1]$ arm-linux-gcc
   
3. .arm-s3c6410-linux-gnueabi-gcc: no input files
   
4. [O_O~/tmp 1]$ which !$
   
5. which arm-linux-gcc
   
6. /home/linyunxian/toolchain/arm-s3c6410-linux-gnueabi/bin/arm-linux-gcc
   

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以上说明bash中可以找到这个环境变量。

1. 
   
2. [O_O~/tmp 1]$ cat make.file
   
3. 
   
4. CC=arm-linux-gcc
   
5. 
   
6. all:
   
7.         echo "$(shell  which $(CC))"
   
8. [~/tmp 1]$ make -f make.file
   
9. echo "/home/linyunxian/toolchain/arm-s3c6410-linux-gnueabi/bin/arm-linux-gcc"
   
10. /home/linyunxian/toolchain/arm-s3c6410-linux-gnueabi/bin/arm-linux-gcc
    

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make 似乎也继承了相应的环境变量

1. 
   
2. [O_O~/tmp 1]$ cat make.file
   
3. 
   
4. # CC=arm-linux-gcc
   
5. CC="/home/linyunxian/toolchain/arm-s3c6410-linux-gnueabi/bin/arm-linux-gcc"
   
6. 
   
7. 
   
8. all:
   
9.         echo "$(shell  $(CC))"
   
10. [~/tmp 1]$ make -f make.file
    
11. .arm-s3c6410-linux-gnueabi-gcc: no input files
    
12. echo ""
    

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用绝对路径表示似乎又没问题。。

把该工具链扔到/usr/local/bin 下  $(shell arm-linux-gcc) 也是没问题的。
“/home/linyunxian/toolchain/arm-s3c6410-linux-gnueabi/bin” 是在~/.bashrc 加入 $PATH 路径中的。该如何解释这个现象呢？

churchmice

回复 1# linyunxian


    参见
lhttp://www.mail-archive.com/help-make@gnu.org/msg06714.html

这网站ms被墙了，所以贴一下内容

Re: Regarding running shell script from Makefile

Paul Smith
Fri, 11 May 2007 12:04:22 -0700

On Fri, 2007-05-11 at 07:15 -0700, gshejin wrote:
> I am having a scenerio where in I have to execute a shell script from
> the Makefile. If I am exporting the path where the shell script is
> located in the PATH variable and then run the make the script get's
> executed. But if i am not exporting the path in the shell and then run
> the make it throws an error, some thing like this

First, when in the world is PATH not exported?  I've never run across an
environment where PATH wasn't exported.

Anyway.  When you say "execute a shell script", do you mean using the
$(shell ...) function, or do you mean a normal command script make
invokes to update a rule?

If the latter, then exporting PATH in your makefile will definitely
work.  If the former, then it won't be enough, because variables that
are marked exported inside the makefile are only exported to command
scripts, not $(shell ...) functions.

To work around this you can use:

        $(shell PATH="$(PATH)" <command>

http://www.mail-archive.com/uclinux-dev@uclinux.org/msg01073.html

[uClinux-dev] [OT] PATH used by make $(shell ) function

John Williams
Wed, 16 May 2007 23:37:03 -0700

Hi,


A bit OT but coming in the context of uClinux-dist, so I'll try here first

Is it possible to modify the PATH used by make's $(shell function)?

The obvious construct

PATH=$(PATH):/path/to/add
export PATH
foo=$(shell mytool)

where mytool lives in /path/to/add, doesn't work

The only way I've got this to fly is like so:

PATH=$(PATH):/path/to/add
foo=$(shell PATH=$(PATH) mytool)

but it's a bit ugly.


Reading the ake manual it's clear that 'export' is intended to send environment variables to sub-makes, but it's silent about how to influence the environment of the $(shell) function. All my experiments here suggest that $(shell) executes with the environment of the shell that invoked make, and there's nothing you can do about that.

cheers,

John

结论就是通过shell函数方式调用，PATH变量是不会被继承的

linyunxian

嗯，我也这么怀疑过。

但makefile中

$(shell export) 和 $(shell which $(cc)) 的输出似乎又说明  PATH 传递下去了。  呜呼。。。。