如何修改传递给自定义CMake目标的环境变量？ [英] How to modify environment variables passed to custom CMake target?

问题描述

也许我缺少一些明显的东西，但我似乎不明白如何显式设置环境变量，可以通过 add_custom_target（） 。

 设定（ENV {PATH}C：/ Some / Path; $ ENV {PATH}）$ b $不幸的是，％PATH％ 
 $ b pre pre pre $ p code>环境变量显示为 somecommand 。 （我设置了一个Gist，可以重现问题，此处。）
 
 
 
我做错了什么？
解决方案
 ，但是在 add_custom_target 中指定的命令在 build 步骤中执行。另请参阅CMake常见问题解答：如何获取或设置环境变量？ 
 
 
 [...] 
 
环境变量 SET  
对于cmake本身（配置时间），
生效，因此您不能使用此方法设置自定义命令可能需要的环境变量
（构建时间）。 
禁止各种CMake命令的环境变量支持
（例如 add_custom_command（），目前尚不支持），
可接受的解决方法可能是
 
 
目前 add_custom_target  code>（和其他命令，其定义构建步骤的动作，例如 add_custom_command ）不支持简单设置环境变量。正如此错误报告中的建议，对于设置变量的值不带空格 em>在Linux上，可以在命令前加上VAR = VAL子句。对于一般情况，您可以准备脚本脚本，其中设置环境并运行实际命令：
 
 
 
在Windows上：
 
 
 
  wrapper.bat ：
  @ECHO OFF 
 PATH =C：\\Some\\Path;％PATH％
％* 
  
  CMakeLists.txt ：
  add_custom_target（... 
 cmd / c $ {CMAKE_CURRENT_SOURCE_DIR} /wrapper.bat< real_command> args ... 
）
  
在Linux上：
 
 
 
  wrapper.sh ：
  exportPATH = / Some / Path：$ PATH
 eval$ *
  
 
 b $ b 
  CMakeLists.txt ：
  add_custom_target（... 
 COMMAND / bin / sh $ {CMAKE_CURRENT_SOURCE_DIR} /wrapper.sh< real_command> args ... 
）
  
如果变量的值取决于配置，您可以使用 configure_file 配置包装脚本。
 
 
 
 strong> UPDATE ：
 
 
 
正如@sakra， env 工具模式 cmake 可用作封装脚本：
  add_custom_target $ b COMMAND $ {CMAKE_COMMAND} -E envPATH = C：/ Some / Path; $ ENV {PATH}< real_command> args ... 
）
  
这种方式自CMake 3.2起可用。
 
Perhaps I am missing something obvious, but I can't seem to figure out how to explicitly set environment variables that can be seen by processes launched through add_custom_target().

I tried the following:
set(ENV{PATH} "C:/Some/Path;$ENV{PATH}")
add_custom_target(newtarget somecommand)
Unfortunately, the %PATH% environment variable appears unchanged to somecommand. (I have set up a Gist that reproduces the problem here.)

What am I doing wrong?
解决方案
You set environment variable at configuration step, but command specified for add_custom_target is executed at build step. See also CMake FAQ: How can I get or set environment variables?

  
[...]

  environment variables SET in the CMakeLists.txt only
  take effect for cmake itself (configure-time),
  so you cannot use this method to set an environment variable
  that a custom command might need (build-time). 
  Barring environment variable support by various CMake commands
  (e.g. add_custom_command(), currently not supported yet),
  an acceptable workaround may be to invoke shell scripts instead
  which wrap the commands to be executed.
Currently add_custom_target (and others commands, which define actions for build step, e.g. add_custom_command) doesn't support simple setting environment variables. As adviced in this bugreport, for set variable's value without spaces on Linux you may prepend command with "VAR=VAL" clauses. For general cases you may prepare wrapper script, which setups environment and run actual command:

On Windows:

wrapper.bat:
@ECHO OFF
set PATH="C:\\Some\\Path;%PATH%"
%*
CMakeLists.txt:
add_custom_target(...
    COMMAND cmd /c ${CMAKE_CURRENT_SOURCE_DIR}/wrapper.bat <real_command> args...
)
On Linux:

wrapper.sh:
export "PATH=/Some/Path:$PATH"
eval "$*"
CMakeLists.txt:
add_custom_target(...
    COMMAND /bin/sh ${CMAKE_CURRENT_SOURCE_DIR}/wrapper.sh <real_command> args...
)
If value of variable depends on configuration, you may configure wrapper script with configure_file.

UPDATE:

As noted by @sakra, env tool mode of cmake executable can be used as a wrapper script:
add_custom_target(...
    COMMAND ${CMAKE_COMMAND} -E env "PATH=C:/Some/Path;$ENV{PATH}" <real_command> args...
)
This way is available since CMake 3.2.

                        
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