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.

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

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

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