make $HOME/.local the default LAMMPS installation destination

cmake/CMakeLists.txt

@@ -11,6 +11,10 @@ get_filename_component(LAMMPS_LIB_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../lib
 get_filename_component(LAMMPS_LIB_BINARY_DIR ${CMAKE_BINARY_DIR}/lib ABSOLUTE)
 get_filename_component(LAMMPS_DOC_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../doc ABSOLUTE)
 
+# by default, install into $HOME/.local (not /usr/local), so that no root access (and sudo!!) is needed
+if (CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+  set(CMAKE_INSTALL_PREFIX "$ENV{HOME}/.local" CACHE PATH "default install path" FORCE )
+endif()
 
 # To avoid conflicts with the conventional Makefile build system, we build everything here
 file(GLOB LIB_SOURCES ${LAMMPS_SOURCE_DIR}/[^.]*.cpp)

cmake/README.md

@@ -195,6 +195,7 @@ cmake -C ../cmake/presets/std_nolib.cmake -D PKG_GPU=on ../cmake
   <td><code>CMAKE_INSTALL_PREFIX</code></td>
   <td>Install location where LAMMPS files will be copied to. In the Unix/Linux case with Makefiles this controls what `make install` will do.</td>
   <td>
+   Default setting is <code>$HOME/.local</code>.
   </td>
 </tr>
 <tr>

doc/src/Build_cmake.txt

@@ -44,7 +44,7 @@ LAMMPS or need to re-compile LAMMPS repeatedly, installation of the
 ccache (= Compiler Cache) software may speed up compilation even more.
 
 After compilation, you can optionally copy the LAMMPS executable and
-library into your system folders (by default under /usr/local) with:
+library into your system folders (by default under $HOME/.local) with:
 
 make install    # optional, copy LAMMPS executable & library elsewhere :pre