Gfortran pre-processor directives for Different Operating systems

Question

Could you tell me please how can I do the following:

#if __unix__
#define path_sep='/'
#elif __windows__
#define path_sep='\'
#else
#error "path_sep not defined."
#endif

using gfortran compiler.

gfortran's manual contains instructions on how to use the preprocessor. Is there anything about them that's not clear to you? — eriktous
– eriktous, Commented Dec 26, 2011 at 17:27

M. S. B. · Accepted Answer · 2011-12-26 14:31:51Z

9

This can be done in combination with conditional compilation and using the "D" option on the command line. Here is some example code:

program test_Dopt
character (len=1) :: pathsep
pathsep = "?"
#ifdef WOS
   pathsep = "\"
#endif
#ifdef UOS
   pathsep = "/"
#endif

write (*, '( "pathsep is >", A1, "<")' )  pathsep

end program test_Dopt

Name the program with filetype F90 to cause gfortran to run the preprocessor or use -cpp on the compile line. Then pass options to the prepreprocessor by including them after D on the compile line, e.g., gfortran -DWOS. (This is more general then gfortran -- most Fortran compilers will process C-style pre-processor directives.) Then you can identify the OS outside of Fortran and pass the information to the Fortran program.

You can compile your code via using the filetype F90 or -cpp.

edited Dec 26, 2011 at 14:31

answered Dec 26, 2011 at 14:08

M. S. B.

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1 Comment

Chris Over a year ago

__unix__ and _WIN32 are the usual predefined preprocessor flags used to indicate which system you are on in most compilers.

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