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Reading files that are locked by other references: c# – Notepad beats them all? – Stack Overflow

Posted by jpluimers on 2018/08/16

Cool feature borrowed from Notepad, which can read files locked by other references (for instance a process having the handle open): [WayBackc# – Notepad beats them all? – Stack Overflow.

The example from the answer is in .NET, but can be used in a native environment as well (Notepad is a native application).

Notepad reads files by first mapping them into memory, rather than using the “usual” file reading mechanisms presumably used by the other editors you tried. This method allows reading of files even if they have an exclusive range-based locks.

You can achieve the same in C# with something along the lines of:

using (var f = new FileStream(processIdPath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
using (var m = MemoryMappedFile.CreateFromFile(f, null, 0, MemoryMappedFileAccess.Read, null, HandleInheritability.None, true))
using (var s = m.CreateViewStream(0, 0, MemoryMappedFileAccess.Read))
using (var r = new StreamReader(s))
    var l = r.ReadToEnd();

Via: [WayBack] Maintaining Notepad is not a full-time job, but it’s not an empty job either – The Old New Thing


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