call program

Author: scivision

cmake/compilers.cmake

@@ -73,7 +73,7 @@ if(NOT f08contig)
 endif()  
 
 if(CMAKE_Fortran_COMPILER_ID STREQUAL Intel)
-  set(FFLAGS -stand f18 -traceback -warn)
+  set(FFLAGS -stand f18 -implicitnone -traceback -warn)
 
   if(CMAKE_BUILD_TYPE STREQUAL Debug)
     list(APPEND FFLAGS -debug extended -check all)

system/CMakeLists.txt

@@ -7,10 +7,15 @@ if(NOT hasParent)
   include(../cmake/compilers.cmake)
 endif()
 
-if(NOT f08command)
+if(hasParent AND NOT f08command)
   return()
+elseif(NOT f08command)
+  message(FATAL_ERROR "Fortran 2008 execute_command_line necessary for these programs.")
 endif()
 
+add_library(osdet os_detect.f90)
+target_compile_options(osdet PRIVATE ${FFLAGS})
+
 add_executable(gitrev gitrev.f90)
 target_compile_options(gitrev PRIVATE ${FFLAGS})
 target_link_libraries(gitrev ${FLIBS})
@@ -24,3 +29,7 @@ add_test(NAME FortranCompiler COMMAND complog)
 add_executable(playsound play_sound.f90)
 target_compile_options(playsound PRIVATE ${FFLAGS})
 target_link_libraries(playsound ${FLIBS})
+
+add_executable(callpython call_python_script.f90)
+target_compile_options(callpython PRIVATE ${FFLAGS})
+target_link_libraries(callpython osdet ${FLIBS})

system/call_python_script.f90

@@ -0,0 +1,31 @@
+program call_python_script
+!! demos calling a Python script, without crashing Fortran program if Python interpreter is not found.
+!! this technique works in general, as Fortran will crash if calling a non-existant program.
+use os_detect, only: getos
+use, intrinsic:: iso_fortran_env, only: stderr=>error_unit
+
+implicit none
+
+integer :: ierr
+character(:), allocatable :: cmd, oscmd, os
+character(*), parameter :: exe='python3'
+
+cmd = "import psutil; print(f'{psutil.virtual_memory().available} MB RAM free')"
+
+os = getos()
+if (os=='windows') then
+  oscmd = 'where '//exe
+elseif(os=='unix') then
+  oscmd = 'which '//exe
+else
+  error stop 'unknown os '//os
+endif
+
+call execute_command_line(oscmd, exitstat=ierr)
+
+if (ierr==0) then
+  call execute_command_line(exe//' -c "'//cmd//'"', exitstat=ierr)
+endif
+if (ierr/=0) write(stderr,*) 'Python psutil not available'
+
+end program

system/os_detect.f90

@@ -0,0 +1,26 @@
+module os_detect
+
+implicit none
+
+contains
+
+function getos()
+!! heuristic detection of operating system based on de factor environment variables
+character(256) :: buf
+character(:), allocatable :: getos
+
+call get_environment_variable("HOME", buf)
+if (len_trim(buf) > 0) then
+  getos = "unix"
+  return
+endif
+
+call get_environment_variable("USERPROFILE", buf)
+if (len_trim(buf) > 0) then
+  getos = "windows"
+  return
+endif
+
+end function getos
+
+end module os_detect