install_name_tool difference between -change and -id

Question

I have been struggling with this concept for a while and I cannot really understand what the difference is between -change and -id.The man page states

 -id name
              Changes  the  shared  library identification name of a dynamic shared library to name.  If the Mach-O binary is not a dynamic
              shared library and the -id option is specified it is ignored.

-change old new
              Changes  the dependent shared library install name old to new in the specified Mach-O binary.  More than one of these options
              can be specified.  If the Mach-O binary does not contain the old install name in a specified -change  option  the  option  is
              ignored.

So far I have experimented with -change. Suppose I have the following structure

Test.App
|_Contents
    |_MacOS
    |   |_test -----> item A
    |_Library
        |_test_library.dylib     --->item B
        |_another_library.dylib  --->item C

Now suppose I ran the following on itemB

$ otool -L test_library.dylib
   test_library.dylib
   /some/path/another_library.dylib  -->item D

The above result indicates that test_library.dylib depends on another_library.dylib now if I needed to change the location of another_library.dylib I would do this

install_name_tool -change /some/path/another_library.dylib some/new/path/another_library.dylib  test_library.dylib 

this would change the location of item D. My question is what does install-name_tool -id do and when do I use that ?

Answer 1

My understanding is:

-id: This sets the "install name" that will be used when linking against the dynamic library. It would be run on the target dynamic library file.

-change: This changes the "install name" after linking and would be run on the executable or dynamic library that links against the target dynamic library.

Answer 2

install-name_tool -id is used for change the install name of dylib, you can use the otool -D see a dylib install name in the terminal, it will show the default value for you, the /some/path/another_library.dylib is the default install name of another _library.dylib, of course, you can change it use install-name_tool -id in the terminal, just use like this in terminal

install-name_tool -id /some/path/another_library_newname.dylib /some/path/another_library.dylib

now,you use the otool -D /some/path/another_library.dylib, you will find the install name is /some/path/another_library_newname.dylib

here is my example in picture