Filename isWritable fails

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.

| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

isWritable
    "Answer true if file is writable by this user.
    Writable for a directory means that new files can be created or old ones renamed."

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.

| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

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Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

"Boris Popov, DeepCove Labs" <[hidden email]> Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" <[hidden email]>, "Gruenewald, Tom" <[hidden email]> Kopie <[hidden email]> Thema RE: [vwnc] Filename isWritable fails

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

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pic17267.gif (1K) Download Attachment

On Windows, #isWritable doesn’t even go that far: look at the code for PCFilename>>isWritable. It just looks at the read-only flag, not ACL permissions.

 

For 7.7.1 there’s Resolution 99501, "UseWin32-ACL-Access to check file accessibility and permissions with MS Windows Access Control List (ACL)". If you request that from support, note that AFAIR it just gives you the mechanism to use ACLs via a DLL – actually changing #isWritable is left to you.

 

Steve

 

From: [hidden email] [[hidden email]] On Behalf Of Gruenewald, Tom
Sent: 12. toukokuuta 2011 16:30
To: Boris Popov, DeepCove Labs; Holger Guhl
Cc: [hidden email]
Subject: [vwnc] Antwort: RE: Filename isWritable fails

 

Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

"Boris Popov, DeepCove Labs" [hidden email]

"Boris Popov, DeepCove Labs" [hidden email] Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" [hidden email], "Gruenewald, Tom" [hidden email] Kopie [hidden email] Thema RE: [vwnc] Filename isWritable fails

Indeed, a lot of the queries against the file system will return errors, even when seemingly innocuous, like #isDirectory, so you need to make sure you have enough error handling in place to deal with these errors.

-Boris

From: [hidden email] [[hidden email]] On Behalf Of Holger Guhl
Sent: 12 May 2011 07:33
To: Gruenewald, Tom
Cc: [hidden email]
Subject: Re: [vwnc] Filename isWritable fails

Tom,
is the code sample just for showing the problem? The code is itself responsible for the failing delete request because it opens the file with "a writeStream". Technically, this registers an open file handle at the OS which then inhibits destroying the file from any process, even if it's the same image that holds the open file. After closing the file associated with "aStream", the delete request should work.
And no: #isWritable is not the full cover test which can tell in advance whether #delete will be successful. The method comment says
isWritable
"Answer true if file is writable by this user.
Writable for a directory means that new files can be created or old ones renamed."
There is a more through test called #canBeWritten, but again, it cannot foresee whether the file is still in use by this or another process.

hope that helps
Holger

Am 12.05.2011 12:53, schrieb Gruenewald, Tom:

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

----------------------------------------
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Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

"Boris Popov, DeepCove Labs" [hidden email]

"Boris Popov, DeepCove Labs" [hidden email] Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" [hidden email], "Gruenewald, Tom" [hidden email] Kopie [hidden email] Thema RE: [vwnc] Filename isWritable fails

Indeed, a lot of the queries against the file system will return errors, even when seemingly innocuous, like #isDirectory, so you need to make sure you have enough error handling in place to deal with these errors.

-Boris

From: [hidden email] [[hidden email]] On Behalf Of Holger Guhl
Sent: 12 May 2011 07:33
To: Gruenewald, Tom
Cc: [hidden email]
Subject: Re: [vwnc] Filename isWritable fails

Tom,
is the code sample just for showing the problem? The code is itself responsible for the failing delete request because it opens the file with "a writeStream". Technically, this registers an open file handle at the OS which then inhibits destroying the file from any process, even if it's the same image that holds the open file. After closing the file associated with "aStream", the delete request should work.
And no: #isWritable is not the full cover test which can tell in advance whether #delete will be successful. The method comment says
isWritable
"Answer true if file is writable by this user.
Writable for a directory means that new files can be created or old ones renamed."
There is a more through test called #canBeWritten, but again, it cannot foresee whether the file is still in use by this or another process.

hope that helps
Holger

Am 12.05.2011 12:53, schrieb Gruenewald, Tom:

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

----------------------------------------
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_______________________________________________
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----------------------------------------
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Hello Holger. Hello forum.
Thank you all for your answers.

I have played with my last code example. And now I am confused.

When I try to delete an already open file, I will get an error sharing violation. I totally agree with this behavior.
But I can write - from the outer scope - into the same file without any problem. I would expect also an error sharing violation here. But instead I get a messy output result.

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b readWriteStream.

[bStream nextPutAll: 'Stream B: Hello World'.
bStream flush.
aStream cr.
aStream nextPutAll: 'Stream A: Hello World'.
aStream flush.
bStream reset.
(contents := bStream contents) isEmpty
ifTrue: [Error raiseSignal: 'Empty file']
ifFalse: [Transcript show: contents]]
ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Holger Guhl <[hidden email]> Gesendet von: [hidden email] 12.05.2011 19:11

An "Gruenewald, Tom" <[hidden email]> Kopie "Boris Popov, DeepCove Labs" <[hidden email]>, [hidden email] Thema Re: Antwort: RE: [vwnc] Filename isWritable fails

Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?


| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

"Boris Popov, DeepCove Labs" [hidden email]



"Boris Popov, DeepCove Labs" [hidden email] Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" [hidden email], "Gruenewald, Tom" [hidden email] Kopie [hidden email] Thema RE: [vwnc] Filename isWritable fails


Indeed, a lot of the queries against the file system will return errors, even when seemingly innocuous, like #isDirectory, so you need to make sure you have enough error handling in place to deal with these errors.

-Boris

From: [hidden email] [[hidden email]] On Behalf Of Holger Guhl
Sent: 12 May 2011 07:33
To: Gruenewald, Tom
Cc: [hidden email]
Subject: Re: [vwnc] Filename isWritable fails

Tom,
is the code sample just for showing the problem? The code is itself responsible for the failing delete request because it opens the file with "a writeStream". Technically, this registers an open file handle at the OS which then inhibits destroying the file from any process, even if it's the same image that holds the open file. After closing the file associated with "aStream", the delete request should work.
And no: #isWritable is not the full cover test which can tell in advance whether #delete will be successful. The method comment says
isWritable
"Answer true if file is writable by this user.
Writable for a directory means that new files can be created or old ones renamed."
There is a more through test called #canBeWritten, but again, it cannot foresee whether the file is still in use by this or another process.

hope that helps
Holger

Am 12.05.2011 12:53, schrieb Gruenewald, Tom:

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

----------------------------------------
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_______________________________________________
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pic21718.gif (1K) Download Attachment

file := 'dentalshare.log' asFilename appendStream.
...
[logging] whileTrue:
    ["log output example:"
    file print: 2; space; print: Timestamp now; cr; close]

Hello Holger. Hello forum.
Thank you all for your answers.

I have played with my last code example. And now I am confused.

When I try to delete an already open file, I will get an error sharing violation. I totally agree with this behavior.
But I can write - from the outer scope - into the same file without any problem. I would expect also an error sharing violation here. But instead I get a messy output result.

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b readWriteStream.

[bStream nextPutAll: 'Stream B: Hello World'.
bStream flush.
aStream cr.
aStream nextPutAll: 'Stream A: Hello World'.
aStream flush.
bStream reset.
(contents := bStream contents) isEmpty
ifTrue: [Error raiseSignal: 'Empty file']
ifFalse: [Transcript show: contents]]
ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

The Transcript output is: "Stream B: Hello Worldld"

Why does no error sharing violation pop up here?

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346
Holger Guhl [hidden email]

Holger Guhl [hidden email] Gesendet von: [hidden email] 12.05.2011 19:11

An "Gruenewald, Tom" [hidden email] Kopie "Boris Popov, DeepCove Labs" [hidden email], [hidden email] Thema Re: Antwort: RE: [vwnc] Filename isWritable fails

Yes, that's the case: #isWritable checks the basic write-access permission without consulting the ACL (MS Access Control List). Effectively, that's not more than checking the file access flags. The #canBeWritten test goes a bit further, but also no ACL check there.
Even in Vista/Win7 with those tricky and obscure file system conditions you can go far with those basic checks, as long as the application deals with files in its "own directories". When it comes to navigating out of this scope you may easily encounter more file access violations.
But as already said: You are seeing a file sharing violation where ACL checks won't help.

Cheers
Holger

Am 12.05.2011 15:30, schrieb Gruenewald, Tom:

Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?


| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

"Boris Popov, DeepCove Labs" [hidden email]



"Boris Popov, DeepCove Labs" [hidden email] Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" [hidden email], "Gruenewald, Tom" [hidden email] Kopie [hidden email] Thema RE: [vwnc] Filename isWritable fails


Indeed, a lot of the queries against the file system will return errors, even when seemingly innocuous, like #isDirectory, so you need to make sure you have enough error handling in place to deal with these errors.

-Boris

From: [hidden email] [[hidden email]] On Behalf Of Holger Guhl
Sent: 12 May 2011 07:33
To: Gruenewald, Tom
Cc: [hidden email]
Subject: Re: [vwnc] Filename isWritable fails

Tom,
is the code sample just for showing the problem? The code is itself responsible for the failing delete request because it opens the file with "a writeStream". Technically, this registers an open file handle at the OS which then inhibits destroying the file from any process, even if it's the same image that holds the open file. After closing the file associated with "aStream", the delete request should work.
And no: #isWritable is not the full cover test which can tell in advance whether #delete will be successful. The method comment says
isWritable
"Answer true if file is writable by this user.
Writable for a directory means that new files can be created or old ones renamed."
There is a more through test called #canBeWritten, but again, it cannot foresee whether the file is still in use by this or another process.

hope that helps
Holger

Am 12.05.2011 12:53, schrieb Gruenewald, Tom:

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

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Hello Holger. Hello forum.
>> It's allowed to open a file for writing from different processes. That's not a VisualWorks feature but allowed by the Operation System. It's up to programmers to make sure they don't create messy file contents.
Just for my personal interest. How can I flag a file as locked for the OS? And will this lock automatically released after the program was finished?

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346
Holger Guhl <[hidden email]>

Holger Guhl <[hidden email]> Gesendet von: [hidden email] 13.05.2011 14:04

An "Gruenewald, Tom" <[hidden email]> Kopie [hidden email] Thema Re: [vwnc] Filename isWritable fails

Hello Holger. Hello forum.
Thank you all for your answers.

I have played with my last code example. And now I am confused.

When I try to delete an already open file, I will get an error sharing violation. I totally agree with this behavior.
But I can write - from the outer scope - into the same file without any problem. I would expect also an error sharing violation here. But instead I get a messy output result.

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b readWriteStream.

[bStream nextPutAll: 'Stream B: Hello World'.
bStream flush.
aStream cr.
aStream nextPutAll: 'Stream A: Hello World'.
aStream flush.
bStream reset.
(contents := bStream contents) isEmpty
ifTrue: [Error raiseSignal: 'Empty file']
ifFalse: [Transcript show: contents]]
ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

The Transcript output is: "Stream B: Hello Worldld"

Why does no error sharing violation pop up here?

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346
Holger Guhl [hidden email]



Holger Guhl [hidden email] Gesendet von: [hidden email] 12.05.2011 19:11

An "Gruenewald, Tom" [hidden email] Kopie "Boris Popov, DeepCove Labs" [hidden email], [hidden email] Thema Re: Antwort: RE: [vwnc] Filename isWritable fails


Yes, that's the case: #isWritable checks the basic write-access permission without consulting the ACL (MS Access Control List). Effectively, that's not more than checking the file access flags. The #canBeWritten test goes a bit further, but also no ACL check there.
Even in Vista/Win7 with those tricky and obscure file system conditions you can go far with those basic checks, as long as the application deals with files in its "own directories". When it comes to navigating out of this scope you may easily encounter more file access violations.
But as already said: You are seeing a file sharing violation where ACL checks won't help.

Cheers
Holger

Am 12.05.2011 15:30, schrieb Gruenewald, Tom:

Hello Holger.
Yes. The code snippet should only show the problem.

So #isWritable tells if the active user has the common OS write permission for a file and not if the file is writable in runtime?

| file a b aStream bStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
[bStream := b writeStream.
[bStream nextPutAll: 'Hello World'] ensure: [bStream close]]]
ensure:
[aStream close.
a delete]

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

"Boris Popov, DeepCove Labs" [hidden email]


"Boris Popov, DeepCove Labs" [hidden email] Gesendet von: [hidden email] 12.05.2011 15:00

An "Holger Guhl" [hidden email], "Gruenewald, Tom" [hidden email] Kopie [hidden email] Thema RE: [vwnc] Filename isWritable fails


Indeed, a lot of the queries against the file system will return errors, even when seemingly innocuous, like #isDirectory, so you need to make sure you have enough error handling in place to deal with these errors.

-Boris

From: [hidden email] [[hidden email]] On Behalf Of Holger Guhl
Sent: 12 May 2011 07:33
To: Gruenewald, Tom
Cc: [hidden email]
Subject: Re: [vwnc] Filename isWritable fails

Tom,
is the code sample just for showing the problem? The code is itself responsible for the failing delete request because it opens the file with "a writeStream". Technically, this registers an open file handle at the OS which then inhibits destroying the file from any process, even if it's the same image that holds the open file. After closing the file associated with "aStream", the delete request should work.
And no: #isWritable is not the full cover test which can tell in advance whether #delete will be successful. The method comment says
isWritable
"Answer true if file is writable by this user.
Writable for a directory means that new files can be created or old ones renamed."
There is a more through test called #canBeWritten, but again, it cannot foresee whether the file is still in use by this or another process.

hope that helps
Holger

Am 12.05.2011 12:53, schrieb Gruenewald, Tom:

Hello forum.
Is #isWritable not the appropriate test method to check if a file can be deleted?
I get an error sharing violation.
| file a b aStream |
file := 'c:\foo.txt'.
a := file asFilename.
aStream := a writeStream.

[b := file asFilename.
(b exists and: [b isWritable])
ifTrue:
["ERROR_SHARING_VIOLATION (IO Error 32)"
b delete]]
ensure:
[aStream close.
a delete]

Thank you for you answers.

Best regards,
Tom Grünewald

________

Carl Zeiss Industrielle Messtechnik GmbH
Softwareentwicklung/Software Development

T o m G r ü n e w a l d

73446 Oberkochen, Germany
tel: +49.7364.20-8541
fax: +49.7364.20-4800
email: [hidden email]
http://www.zeiss.de/imt

Carl Zeiss Industrielle Messtechnik GmbH
Carl–Zeiss–Straße 22, 73447 Oberkochen
Aufsichtsratsvorsitzender: Dr. Hermann Gerlinger
Geschäftsführer: Dr. Rainer Ohnheiser, Felix Hoben, Axel Jaeger
Sitz der Gesellschaft: 73446 Oberkochen, Deutschland
Handelsregister: Amtsgericht Ulm, HRB 501561
USt–IdNr.: DE 811 515 346

----------------------------------------
This message is intended for a particular addressee only and may contain business or company secrets. If you have received this email in error, please contact the sender and delete the message immediately. Any use of this email, including saving, publishing, copying, replication or forwarding of the message or the contents is not permitted.




_______________________________________________
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