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

Declaration

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

Argument definitions

file-ref

The vfs.file object associated with the file to be truncated.

absolute

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.
  
  process
     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.

Exceptions

The following exceptions may occur:

• VFS200 The vfsFile object must be opened before it can be used
• VFS206 The file 'X' must be opened with write access to enable writing to it
• VFS209 An invalid value was specified for the absolute cursor movement
• VFS300 Generic operating system error

Related Topics vfs.open vfs.file

Other Library Functions vfs.change-directory vfs.change-owner vfs.change-permissions vfs.close vfs.connect vfs.connect-directory vfs.copy vfs.cursor-position vfs.default-certificates-file vfs.delete-directory vfs.delete-file vfs.describe vfs.describe-file vfs.directory vfs.directory-name vfs.disconnect vfs.file vfs.file-directory vfs.file-name vfs.link vfs.list vfs.lock vfs.make-directory vfs.move vfs.move-cursor vfs.omvfs-version vfs.open vfs.open-file-system vfs.open-ftp vfs.open-http vfs.open-https vfs.reader vfs.set-default-certificates-file vfs.truncate vfs.unlock vfs.writer

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