Library: File system utilities (OMVFS)
Import : omvfs.xmd

export external function truncate
                value file file-ref
        at      value integer absolute optional

Argument definitions

The vfs.file object associated with the file to be truncated.
The byte position at which the file will be truncated. The number of bytes remaining in the file will be equal to the value of this parameter.


You can use vfs.truncate to truncate a file. The following program will truncate the specified file after the 5th byte:

  import "omvfs.xmd" prefixed by vfs.
     local vfs.file too-long
     set too-long 
      to vfs.open "c:\temp\test.txt" 
      for vfs.read-write-mode
     vfs.truncate too-long at 5

This function will always leave the file with a number of bytes equal to the specified value. To empty a file, specifiy a value of 0 or vfs.start-offset. If the value specified is greater than the current size of the file, the file will be padded with null bytes up to the specified length.

If you do not specify the absolute position at which to truncate the file, it will be truncated at the current position. You can determine the current cursor position with vfs.cursor-position.


The following exceptions may occur:

Related Topics