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Windows: ftruncate to shrink file gives EPERM #3177
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/cc @nodejs/platform-windows - I don't know the answer to this question. I thought that as long as you have the appropriate privileges and the file is opened for writing (not appending), you should be able to truncate it in either direction.
Thanks Ben, that was the problem. I had the file opened on Windows using "a+".
On Mac however, ftruncate still works if the file is opened with "a+".
This behaviour is undocumented in node, and I'd welcome a PR for that, but node doesn't reduce Windows and Unixen to a "lowest common denominator", there are differences.
I have a file with the following stats in a Windows VM:
{"dev":-24039965,"mode":33206,"nlink":1,"uid":0,"gid":0,"rdev":0,"ino":562949953548321,"size":39035842,"atime":"2015-10-03T09:59:32.677Z","mtime":"2015-10-03T10:00:17.241Z","ctime":"2015-10-03T10:00:17.241Z","birthtime":"2015-10-03T09:59:32.677Z"}
Truncating this file using ftruncate from 39035842 to 38839234 byte (to make it smaller) gives EPERM.
Is ftruncate simply not supported at all on Windows? I thought it was only ftruncate to enlarge a file that was not permitted on Windows?