[CMake] How to set Overwrite or no over write in install(FILES ....)?

[Eric Noulard]

2013/3/11 hce <jupiter.hce at gmail.com>:
> Andreas Stahl wrote
>> Hello Jupiter,
>>
>> can you post the error message here? I wasn't aware that install(FILES
>> ...) did any checking besides comparing the dates and overwriting if the
>> file to be installed is newer.
>> Also, you misunderstood what Petr meant. You need to escape the quotes in
>> the install(CODE "...") call, because you're effectively writing a string
>> to a file, i.e.:
>>
>>  install(CODE "
>>   if (NOT EXISTS \"${destination}/myfile.txt\")
>>         install(FILES \"${source}/myfile.txt\" DESTINATION ${destination})
>>     endif()
>>  ")
>>
>> BUT: using install inside an install command smells like problems, so you
>> better use the file(INSTALL...) directive, anyway:
>>
>>  install(CODE "
>>   if (NOT EXISTS \"${destination}/myfile.txt\")
>>         file(INSTALL \"${source}/myfile.txt\" DESTINATION
>> \"${destination}\")
>>     endif()
>>  ")
>>
>> using the SCRIPT signature expects a cmake script file that will be
>> included in the cmake_install.cmake script file. This means you would need
>> to configure your paths in your cmakelists file
>>
>>  configure_file(myfile_install.cmake.in myfile_install.cmake)
>>  install(SCRIPT myfile_install.cmake)
>>
>> and in myfile_install.cmake.in you'd put
>>
>>  if(NOT EXISTS "${destination}/myfile.txt")
>>    file(INSTALL "${source}/myfile.txt" DESTINATION "${destination}")
>>  endif()
>>
>> Hope that helps,
>>
>> Andreas
>
> Ahh, that's tricky, the file(INSTALL ....) works. Thank you so much Andreas,
> and thanks Petr for your kind helps.

You should keep in mind that actions takes place at different "time":

CMake/Configure time - when cmake runs and configure your source (when
the CMakeLists.txt are read)
Build time - when you compile
Install time - when you use the "make install" or build the "install"
target with your favorite build tool
CPack time - when CPack runs, during this step the CPack generator is
running and CPack itself
                      is running a "CPack install time"  step which
install things in a CPack-private location
                      <buildtree>/_CPack_Packages/...
Package Install time - when the package itself (RPM, DEB, ZIP, NSIS)
is installed.

have a look at slides 15 and 16 here:
https://github.com/TheErk/CMake-tutorial/blob/master/CMake-tutorial-8feb2012.pdf

install(...) command found in CMakeLists.txt is processed at CMake-time
which creates a set of cmake_install.cmake files which get used
at "Install time" or "CPack time::CPack install time".

The [CMake] command you can use without trouble in
  install(SCRIPT
 or
  install(CODE

are "scriptable" commands, the one you use when using cmake -P.
That why you find
file(INSTALL ...)
in cmake_install.cmake and no install(TARGET ...), "install" is not scriptable.

At "Package Install time" you have what your packaging system offers and usually
you dont expect to have CMake running at this point.

I hope this clarifies the process.
Depending on "when" you expect action to take place drive "how" you can do it.

-- 
Erk
Le gouvernement représentatif n'est pas la démocratie --
http://www.le-message.org