3 Runtime: Influencing runtime behavior with environment variables

The behavior of the gfortran can be influenced by environment variables.

Malformed environment variables are silently ignored.

• GFORTRAN_STDIN_UNIT: Unit number for standard input
• GFORTRAN_STDOUT_UNIT: Unit number for standard output
• GFORTRAN_STDERR_UNIT: Unit number for standard error
• GFORTRAN_USE_STDERR: Send library output to standard error
• GFORTRAN_TMPDIR: Directory for scratch files
• GFORTRAN_UNBUFFERED_ALL: Don't buffer I/O for all units.
• GFORTRAN_UNBUFFERED_PRECONNECTED: Don't buffer I/O for preconnected units.
• GFORTRAN_SHOW_LOCUS: Show location for runtime errors
• GFORTRAN_OPTIONAL_PLUS: Print leading + where permitted
• GFORTRAN_DEFAULT_RECL: Default record length for new files
• GFORTRAN_LIST_SEPARATOR: Separator for list output
• GFORTRAN_CONVERT_UNIT: Set endianness for unformatted I/O
• GFORTRAN_ERROR_DUMPCORE: Dump core on run-time errors
• GFORTRAN_ERROR_BACKTRACE: Show backtrace on run-time errors