Opening File Ports

The  open-input-file and  open-output-file procedures can take an optional argument after the filename that specifies a mode for the file. This additional argument must be either  'text or  'binary, indicating that the file should be opened using text mode or binary mode. By default, files are opened in binary mode.

The  open-output-file procedure can also take an argument that specifies how to proceed when a file with the specified name already exists:

•  'error -- raise an error (this is the default)
•  'replace -- remove the old file and write a new one
•  'truncate -- overwrite the old data
•  'append -- append to the end of the file

Extra arguments are passed to open-output-file in any order. Appropriate arguments can also be passed as the last argument(s) to  call-with-input-file,  with-input-from-file,  call-with-output-file, and  with-output-to-file. When conflicting arguments are passed to open-output-file,  with-output-to-file, or  call-with-output-file, the  exn:application:mode-conflict exception is raised.