F90_RETURN is a FORTRAN90 program which demonstrates how a FORTRAN90 program can return a program status value.
C and C++ programs can return an integer value signalling the status of the program's execution. By convention, a return value of 0 indicates that the program executed successfully, while a nonzero value indicates some kind of error.
The return value of such a program can be retrieved and used to make decisions. In particular, if the execution of the program is part of a script, then the failure of the program can be detected, and the script can terminate gracefully.
For an example in the BASH shell, we might have a script that reads:
./prog if [ $? -ne 0 ]; then echo "Errors while running prog." exit fiHere, $? is a BASH symbol that returns the most recent program status value, and the script exits if that value is not zero.
FORTRAN has always had the option to include a constant integer value as part of the STOP statement. At least some FORTRAN compilers can treat this value as a program status value that is returned to the calling environment, and hence can signal whether certain errors have occurred.
Here, we show a simple example in which the program is guaranteed to fail, and in that case will return the arbitrary but nonzero value 13.
The computer code and data files described and made available on this web page are distributed under the GNU LGPL license.
F90_RETURN is available in a FORTRAN77 version and a FORTRAN90 version.
You can go up one level to the FORTRAN90 source codes.