# Problem with shell escaping when building from Xcode generated project

**URL:** https://discourse.cmake.org/t/problem-with-shell-escaping-when-building-from-xcode-generated-project/3510
**Category:** Code
**Tags:** os:macos, gen:xcode
**Created:** [June 6, 2021, 5:13pm UTC](https://discourse.cmake.org/t/problem-with-shell-escaping-when-building-from-xcode-generated-project/3510 "2021-06-06T17:13:37Z")
**Posts on this page:** 3
**Page:** 1

<div class="post-metadata">

### Author: ![Zorro666](https://discourse.cmake.org/user_avatar/discourse.cmake.org/zorro666/32/1523_2.png) [@Zorro666](https://discourse.cmake.org/u/Zorro666)
#### Post date: [June 6, 2021, 5:13pm UTC](https://discourse.cmake.org/t/problem-with-shell-escaping-when-building-from-xcode-generated-project/3510/1 "2021-06-06T17:13:37Z")

</div>

I had a problem using a cmake ExternalProject build command when using the Xcode generator and then building from inside Xcode. If one of the shell variables being used contained a special character that required escaping i.e. ~ then the generated Xcode build command produced a shell script that would not run.

I have tried to reproduce the scenario down to a small reproduction project.

The command line used to generate the Xcode project is  
`cmake -H. -Bbuild-xcode -G Xcode`

The CMakeLists.txt file (there is also a dummy “test.cpp” file to allow project generation to proceed).

```
cmake_minimum_required(VERSION 2.8.12)

project(Test)

add_executable(Test test.cpp)

# This builds from inside Xcode
set(TEST "/Users/jake/test")
# This fails to build from inside Xcode
set(TEST "~/test")

add_custom_command(TARGET Test
    POST_BUILD
    COMMAND JAKE=${TEST} echo "JAKE" > /dev/null 2>&1
    )

```

The generated script in the Xcode project for the non-working scenario is:

```
set -e
if test "$CONFIGURATION" = "Debug"; then :
  cd /Users/jake/Workspace/personal/cmakeBug/build-xcode
  "JAKE=~/test" echo JAKE > /dev/null 2>&1
fi

```

and for the working scenario:

```
set -e
if test "$CONFIGURATION" = "Debug"; then :
  cd /Users/jake/Workspace/personal/cmakeBug/build-xcode
  JAKE=/Users/jake/test echo JAKE > /dev/null 2>&1
fi
```

---

<div class="post-metadata">

### Author: ![craig.scott](https://discourse.cmake.org/user_avatar/discourse.cmake.org/craig.scott/32/20_2.png) [@craig.scott](https://discourse.cmake.org/u/craig.scott)
#### Post date: [June 6, 2021, 9:47pm UTC](https://discourse.cmake.org/t/problem-with-shell-escaping-when-building-from-xcode-generated-project/3510/2 "2021-06-06T21:47:35Z")

</div>

You are using shell features in your command line (expansion of `~` and shell redirection), but CMake doesn’t guarantee any particular shell behavior (or even that a shell is used). If you want to use shell features, you should make your command run a shell. For example:

```cmake
add_custom_command(TARGET Test
    POST_BUILD
    COMMAND bash -c "JAKE=${TEST} echo JAKE > /dev/null 2>&1"
    )

```

---

<div class="post-metadata">

### Author: ![Zorro666](https://discourse.cmake.org/user_avatar/discourse.cmake.org/zorro666/32/1523_2.png) [@Zorro666](https://discourse.cmake.org/u/Zorro666)
#### Post date: [June 7, 2021, 5:12am UTC](https://discourse.cmake.org/t/problem-with-shell-escaping-when-building-from-xcode-generated-project/3510/3 "2021-06-07T05:12:36Z")

</div>

Thank you that is very helpful and explains the escaping differences.

Another option I found was this

```
add_custom_command(TARGET Test
    POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E env JAKE=${TEST} echo "JAKE" > /dev/null 2>&1
    )

```

For reference, the full example relates to capturing/setting the PATH environment variable when building an `ExternalProject` from Xcode on Apple Silicon.  
In that scenario, Xcode does not include the brew default install location in the Xcode PATH environment variable (`/opt/homebrew/bin`).  
On Apple Intel the default brew install is included in the Xcode PATH environment `(/usr/local/bin`)