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digitalmars.D - iterate over a directory, dealing with permission errors

reply Daniel Pflager <daniel.pflager gmail.com> writes:
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
.
.
.
```
Jan 21 2022
parent Paul Backus <snarwin gmail.com> writes:
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.
Jan 21 2022