qa.hlp (Table of Contents; Topic list)
Int 21H Function 45H
   Summary  Notes  Back
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▀ A seek, read, or write operation that moves the file pointer for one of
  the two handles also moves the file pointer associated with the other.
 
▀ This function can be used to efficiently update the directory for a file
  that has changed in length, without incurring the overhead of closing and
  then reopening the file. The handle for the file is simply duplicated
  with this function and the duplicate is closed, leaving the original
  handle open for further read/write operations.
 
▀ [3.3+] See also Int 21H Function 68H (Commit File).
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