Library: General, 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 Syntax    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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