file string-expression exists

An operator that tests whether a named file exists. Useful for avoiding overwriting a file that already exists with a new one.

For example, the following shows how a file...exists test can be used to avoid overwriting an existing file:

  global stream error-strm
  ...
  do when file "errors.log" exists
    put #error "File errors.log already exists.%n"
    put #error "Please delete or rename it before running this program.%n"
    halt with 1
  else
    open error-strm as file "errors.log"
  done