vfsTruncate

function

Library: File system utilities (OMVFS legacy)
Include: omvfs.xin

Declaration

define external function vfsTruncate 
         value  vfsFile  file
     at  value  integer  absolute  optional

Argument definitions

file: is the vfsFile object associated with the file to be truncated.

absolute: is the first byte to be deleted.

Purpose

Use vfsTruncate to truncate a file at a specified byte.

Requirements

You must include the following line at the beginning of your OmniMark program:

  include "omvfs.xin"

file must be:

open (external exception VFS200), and
opened for writing (external exception VFS206)

absolute deletes file contents beginning with:

the start of the file when absolute has a value of zero (0)
the start of the file when absolute has a value of VFS-START
byte "absolute" when absolute has a positive value

Specifying any other value for absolute will cause an exception to be thrown (external exception VFS209). All bytes from and including the specified position to the end of the file will be removed from the file.

Usage Notes

If absolute isn't supplied, then it defaults to the current cursor position.

If absolute is greater than the current file size, then the file size in increased to absolute and the new file contents are undefined.

External exception VFS300 is thrown for any general OS operation failure. The text accompanying the exception will contain details on the reason for the failure.

Example:

Truncate a file from byte 200 to the end of the file.

  include "omvfs.xin"
  
  process
     local vfsFile vfsFile2
     set vfsFile2 to vfsOpen "myfile.txt" for VFS-READ-WRITE
     vfsTruncate vfsFile2 at 200

Other Library Functions