Truncate text file windows

After these experiences, one suspects that each system will have its own quirks for some types of file, and testing will be required. One's guilt is not so easily diverted, but, Go has the required function in the standard library. The implementation calls operating system specific functions and returns whatever errors the operating system reports.

This can be achieved by using the setFileSize function in System. Files :. Unicon provides the built-in function truncate which can be used to truncate a file. The following line of code truncates filename to newsizeinbytes. The file is opened for both read and write in untranslated mode. The built-in function for truncating a file in Java will leave the file unchanged if the specified size is larger than the file. This version expects the source file name and the new size as command line arguments in that order.

It is also possible to call API functions to achieve this task. With native means Fileio Xtra file truncation can only be implemented indirectly, either using a temp file or loading truncated file contents into memory, deleting original and writing memory back to file:. But there are also free plugins "Xtras" like e.

Lua treats strings as being invariably one byte per character hence the awkwardness of trying to use it with unicode , so it's safe to use string methods to truncate binary data.

Nim provides the module "posix" which allows to use the Posix functions in Nim programs. The behavior is that of the "truncate" Posix function.

Especially, if the provided length is greater than the current file size, the file is expanded at the requested length with null bytes. The function returns a code which can be checked to emit a message or raise an exception in case of error. In the following example, we ignore discard this return code. The Unix module provided with the standard distribution provides a function truncate :. There is also a function ftruncate that does the equivalent operation but with a file descriptor instead of a file name:.

In honour of this very task, there is now 0. PureBasic has the internal function TruncateFile that cuts the file at the current file position and discards all data that follows.

Racket has a file-truncate function that expects an open port and truncate its associated file. Note that it can also extend the file, and the code below prints a warning in that case.

The external truncate routine could be replaced with the following line in which case no need for NativeCall :. As long as the REXX program has access to enough virtual memory, this version won't have an issue, except for some versions of REXX that are severely limited in virtual storage by design or by the operating system. Extra boilerplate code was added to ensure that various flavors of REXX correctly handle a file that:.

AA being truncated to bytes:. This only works with some platforms. If truncation is not available, then Ruby raises NotImplementedError. I know it existed in Win7, but I do not remember seeing that particular command when I researched this all those years back.

Show 2 more comments. Dan Atkinson 1 1 gold badge 6 6 silver badges 12 12 bronze badges. KipB7 KipB7 77 1 1 silver badge 1 1 bronze badge. This really doesn't seem to answer the question. Zimba Zimba 6 6 silver badges 11 11 bronze badges. If you have GnuWin32 installed, then you can use dd to do it.

Alternatives that works well with big files: trunc. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually.

Linked 4. Related 2. Hot Network Questions. Question feed. Apparently truncate just trashes everything despite the seek ing to near the end. The likely explanation is that the problem is nothing to do with Windows but all to do with the implementation of the R function. On Windows it likely uses a signed 32 bit integer to specify the truncated file size, hence the limitation. It's also plausible that the documentation could be out of date, and that the R developers have now managed to work out how to implement this function correctly on Windows.

So, while truncating huge files probably works on Windows using the Windows API as shown in your code , it may well be that this POSIX -like layer that R uses does not yet fully support this again, see source. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Truncate large file on Windows Ask Question.

Asked 6 years, 3 months ago. Active 6 years, 3 months ago. Viewed 4k times. According to the manual page of the truncate function in R, on some platforms including Windows Update Following hrbrmstr's reference to this R bugzilla link , I tried some R code to verify whether the truncate function works properly on Windows 8. Improve this question.