Thread overview
Careful when using chdir inside a dirEntries loop
Jun 09, 2011
Andrej Mitrovic
Jun 09, 2011
Jonathan M Davis
Jun 09, 2011
Andrej Mitrovic
June 09, 2011
Here's a little buggy code which most often throws an exception:

    foreach (string entry; dirEntries(curdir, SpanMode.shallow))
    {
        if (entry.isdir)
        {
            foreach (string subentry; dirEntries(entry, SpanMode.shallow))
            {
                if (subentry.isdir)
                {
                    chdir(rel2abs(subentry));
                }
            }
        }
    }

Usually throws something like:
std.file.FileException@std\file.d(1124): .\foo\bar.d: The system cannot find the path specified.

The problem is, chdir will modify curdir and dirEntries doesn't store 'curdir' internally as an absolute address.

The way to work around this is to call rel2abs as soon as possible when using 'curdir' (the first line changed):

    foreach (string entry; dirEntries(rel2abs(curdir), SpanMode.shallow))
    {
        if (entry.isdir)
        {
            foreach (string subentry; dirEntries(entry, SpanMode.shallow))
            {
                if (subentry.isdir)
                {
                    chdir(rel2abs(subentry));
                }
            }
        }
    }

I've had a use for code like this because where I was invoking a batch file which was always relative to the current subdirectory. But anyways, I just thought I'd throw it out in case anyone else runs into this.
June 09, 2011
On 2011-06-09 15:20, Andrej Mitrovic wrote:
> Here's a little buggy code which most often throws an exception:
> 
> foreach (string entry; dirEntries(curdir, SpanMode.shallow))
> {
> if (entry.isdir)
> {
> foreach (string subentry; dirEntries(entry, SpanMode.shallow))
> {
> if (subentry.isdir)
> {
> chdir(rel2abs(subentry));
> }
> }
> }
> }
> 
> Usually throws something like: std.file.FileException@std\file.d(1124): .\foo\bar.d: The system cannot find the path specified.
> 
> The problem is, chdir will modify curdir and dirEntries doesn't store 'curdir' internally as an absolute address.
> 
> The way to work around this is to call rel2abs as soon as possible when using 'curdir' (the first line changed):
> 
> foreach (string entry; dirEntries(rel2abs(curdir), SpanMode.shallow))
> {
> if (entry.isdir)
> {
> foreach (string subentry; dirEntries(entry, SpanMode.shallow))
> {
> if (subentry.isdir)
> {
> chdir(rel2abs(subentry));
> }
> }
> }
> }
> 
> I've had a use for code like this because where I was invoking a batch file which was always relative to the current subdirectory. But anyways, I just thought I'd throw it out in case anyone else runs into this.

I'm not sure if that's a valid bug or not. It could easily be a case of "just don't do that," or it could be that dirEntries needs to be improved. Open a bug report on it so that it's at least recorded and known. Then we can decide the best course of action to take with it.

- Jonathan M Davis
June 09, 2011
Ok filed. I don't know whether it's a bug or not, I do think it's a subtle issue worth investigating though.