Currently implemented utilities:
- xcrun
- xcode-select
xcode-select is a simple utility used to specify the location of a Developer folder.
- What is a Developer folder? and why do we need to select one?
A Developer folder is a special folder that contains your SDK and it's associated Toolchain.
By selecting a Developer folder, tools like xcrun will be able to locate resources found in the Developer folder.
- How does this tool work?
When you select a Developer folder, it's absolute path will be written to a configuration file called ~/.xcdev.dat for other utilities to use.
NOTE: It is not recommended that you modify this file directly!
- How do I use this tool?
The functionality of xcode-select is almost identical to that of Apple's xcode-select utility.
To select a Developer folder, simply run xcode-select --switch /path/to/DevFolder.
To display the absolute path of a Developer folder, simply run xcode-select --print-path.
Other options are --version to display version information and --help to display usage information.
If you only wish to temporarily override the Developer folder path, set the DEVELOPER_DIR environment variable
in your shell to point to the absolute path of your desired Developer folder.
xcrun is a simple utility used to locate and/or execute Developer, Toolchain, and SDK tools.
- How does this tool work?
xcrun works by searching and optionally executing tools located within the Developer folder. When xcrun is invoked, it will search paths in the following order:
```
/<DevFolder>/usr/bin
/<DevFolder>/SDKs/<specified sdk>.sdk/usr/bin
/<DevFolder>/Toolchains/<associated toolchain>.toolchain/usr/bin
```
Where <DevFolder> represents the Developer folder, and <specified sdk> and <associated toolchain> represents the
specified SDK and associated toolchain.
If no SDK is specified while running xcrun, a default SDK which is specified in /etc/xcrun.ini will be used.
When xcrun is told to use an sdk that is either specified by the user or specified by /etc/xcrun.ini, xcrun will read
a configuration file called /<DevFolder>/SDKs/<specified sdk>.sdk/info.ini which is used to resolve the toolchain name and the deployment target used.
Below is an example of an info.ini file found in an SDK folder. For this example, our SDK name is DarwinARM, and the file name combined with it's
absolute path will be /Developer/SDKs/DarwnARM.sdk/info.ini:
```
[SDK] ; this is an sdk configuration file
name = DarwinARM ; this is the name of our SDK. This MUST match the folder name that is postfixed with '.sdk'.
version = 1.0.0 ; this is the version number for the SDK.
default_arch = arm ; this is the default architecture to be used for the SDK
toolchain = DarwinARM ; this is the specified toolchain name to be used with the SDK.
macosx_deployment_target = 10.7 ; this is the deployment target to be used with the SDK.
; you can rename this variable to ios_deployment_target and set it to an appropriate iOS version
; (e.g.: ios_deployment_target = 4.3.5) if you are building iOS software.
```
NOTE: All information written into info.ini is case-sensitive (except comments), so take extra care when writing your own.
After xcrun has retrieved the information found in the SDK's info.ini, it will then validate the toolchain to use for the SDK by
parsing the Toolchain's info.ini, which is assumed to be located in /<DevPath>/Toolchains/<associated toolchain>.toolchain.
Below is an example of an info.ini file found in the Toolchain folder. For this example, our Toolchain name is DarwinARM, and the file name combined with it's
absolute path will be /Developer/Toolchains/DarwinARM.toolchain/info.ini:
```
[TOOLCHAIN] ; this is a toolchain configuration file
name = DarwinARM ; this is the name of our Toolchain. This MUST match the folder name that is postfixed with '.toolchain'.
version = 1.0.0 ; this is the version number for the toolchain
```
After the SDK and Toolchain paths have been resolved, xcrun will then proceed to search the resolved paths for the tool called. Assuming that our SDK and Toolchain information matches the examples shown above, xcrun will search the following paths for the tool:
```
/Developer/usr/bin
/Developer/SDKs/DarwinARM.sdk/usr/bin
/Developer/Toolchains/DarwinARM.toolchain/usr/bin
```
By default, xcrun will locate and execute tools that are passed to it. If you only wish to find a tool's path, you must use the --find
option followed by the tool name when invoking xcrun. This is further explained in the next section.
Once xcrun has located a tool to be executed, it will pass the following environment variables to the called tool:
```
SDKROOT - This points to the specified SDK folder (e.g. <DevFolder>/SDKs/<specified sdk>.sdk).
PATH - This contains all resolved paths for the Developer folder, the SDK, the Toolchain, and the hosts' $PATH in order.
HOME - This contains the path to the current user's home directory (used internally for recursive calls to xcrun).
TARGET_TRIPLE - This is set to an llvm target triple that is associated with the currently selected SDK.
IOS_DEPLOYMENT_TARGET - If MACOSX_DEPLOYMENT_TARGET isn't specified and this is, this will be passed to the called tool.
MACOSX_DEPLOYMENT_TARGET - If IOS_DEPLOYMENT_TARGET isn't specified and this is, this will be passed to the called tool.
```
If IOS_DEPLOYMENT_TARGET or MACOSX_DEPLOYMENT_TARGET are set in your shell, the deployment target specified by the SDK will be overridden.
NOTE: Ensure that only one of these variables are set at a time if they are used, otherwise things may break!
- How do I use this tool?
Below is a list of all supported options:
-h, --help show this help message and exit
--version show the xcrun version
-v, --verbose show verbose logging output
--sdk <sdk name> find the tool for the given SDK name
--toolchain <name> find the tool for the given toolchain
-l, --log show commands to be executed (with --run)
-f, --find only find and print the tool path
-r, --run find and execute the tool (the default behavior)
--show-sdk-path show selected SDK install path
--show-sdk-version show selected SDK version
--show-sdk-target-triple show selected SDK target triple
--show-sdk-toolchain-path show selected SDK toolchain path
--show-sdk-toolchain-version show selected SDK toolchain version
-
Running the Developer tool
image3maker:xcrun image3maker -f mach_kernel -t krnl -o mach.img3 -
Running the Toolchain tool
otoolwith the default SDK (implying it's associated Toolchain):xcrun otool -L /Developer/SDKs/DarwinARM.sdk/usr/lib/system/libsystem_kernel.dylib -
Running the Toolchain tool
clangwith the DarwinARM SDK:xcrun -sdk DarwinARM clang -arch armv7 -x c -g -O2 hello.c -o hello -lSystem -
Running the Toolcain tool
clangwith the DarwinARM Toolchain:xcrun -toolchain DarwinARM clang -arch armv7 -x c -g -O2 hello.c -o hello -lSystem -
Locating the Toolchain tool
lipowith the default SDK:xcrun -find lipo -
Locating the Toolchain tool
lipowith the DarwinARM SDK:xcrun -sdk DarwinARM -find lipo
xcrun also supports multicall behavior. Below is a small list of symbolic links to xcrun that exhibit special behavior:
```xcrun_verbose``` - calls xcrun in verbose mode, like passing the --verbose option to xcrun
```xcrun_log``` - calls xcrun in logging mode, like passing the --log option to xcrun
You may also create symbolic links to xcrun that match the name of a tool that may be found in the Developer folder or default SDK or Toolchain folders. For example:
```
$ ln -s /usr/bin/xcrun ./image3maker
$ ./image3maker
No input file
Usage: image3maker [options]
Generate an Image3 file.
-c, --certificateBlob [file] Use file as a certificate to add to the image.
-f, --dataFile [file] Use file as an input. (required)
...
```
NOTE: If this is your first time using this version of xcrun and you run into an error starting with xcrun: error: unable to validate path,
ensure that xcrun is searching the developer folder by running xcode-select --switch <DevPath>, where <DevPath> is the absolute path to your
developer folder. If you still run into problems, open an issue report and maybe I can help you. :)