iterate over a directory, dealing with permission errors

January 22, 2022

Posted by Daniel Pflager

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Daniel Pflager

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https://forum.dlang.org/post/pldneecaysxueshzwopx@forum.dlang.org

On Sunday, 23 May 2021 at 15:19:34 UTC, xray wrote:

On Sunday, 23 May 2021 at 15:13:31 UTC, Mike Parker wrote:

On Sunday, 23 May 2021 at 15:12:22 UTC, Mike Parker wrote:

Are you calling it with RangePrimitive.pop or RangePrimitive.popFront?

I meant, RangePrimitive.front or RangePrimitive.popFront.

RangePrimitive.popFront

In SpanMode.depth I still get the FileException and in SpanMode.breadth, the program hangs for ever.

I've got a test environment set up.

DMD32 D Compiler v2.098.0-dirty
Copyright (C) 1999-2021 by The D Language Foundation, All Rights Reserved written by Walter Bright

Windows 10 Enterprise (1909) OS Build 18363.2037

Test program (fixit.d):

import std.exception;
import std.file;
import std.stdio;

int main(string[] args) {
	// Use glob to search by glob pattern
	foreach (string name; dirEntries(args[1], SpanMode.breadth, false).handle!(FileException, RangePrimitive.popFront, (e, r) => DirEntry())) {
		writeln(name);
	}
	return 0;
}

Using git bash shell GNU bash, version 4.4.23(1)-release (x86_64-pc-msys)

time ./fixit.exe C:\\

Results in ...

C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
C:\$Recycle.Bin\S-1-5-21-2025429265-1303643608-1417001333-1255143\$RTQTCU0.1-javadoc
.
.
.

On Saturday, 22 January 2022 at 02:09:39 UTC, Daniel Pflager wrote:

https://forum.dlang.org/post/pldneecaysxueshzwopx@forum.dlang.org

On Sunday, 23 May 2021 at 15:19:34 UTC, xray wrote:

On Sunday, 23 May 2021 at 15:13:31 UTC, Mike Parker wrote:

On Sunday, 23 May 2021 at 15:12:22 UTC, Mike Parker wrote:

Are you calling it with RangePrimitive.pop or RangePrimitive.popFront?

I meant, RangePrimitive.front or RangePrimitive.popFront.

RangePrimitive.popFront

In SpanMode.depth I still get the FileException and in SpanMode.breadth, the program hangs for ever.

[...]

Test program (fixit.d):

import std.exception;
import std.file;
import std.stdio;

int main(string[] args) {
	// Use glob to search by glob pattern
	foreach (string name; dirEntries(args[1], SpanMode.breadth, false).handle!(FileException, RangePrimitive.popFront, (e, r) => DirEntry())) {
		writeln(name);
	}
	return 0;
}

Unfortunately, there is no easy workaround for this. Because the exception is thrown by popFront, the front of the range can never actually be popped, and iteration cannot advance beyond the problematic element. Catching the exception and retrying popFront will just give the exact same error again, as you've seen.

Probably the best you can do (without implementing your own dirEntries iterator from scratch) is to use SpanMode.shallow to iterate over each individual directory with a separate loop. A permission error will still force you to skip the directory it occurs in, but you will be able to continue on to other files and directories adjacent to it.

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