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[Glass] Is there a Smalltalk way to lock a file?

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Mariano Martinez Peck

[Glass] Is there a Smalltalk way to lock a file?

Hi guys,

Do we have a method to lock a file at the OS level? I searched in image but I cannot find anything. If it would work in gemstone too that would be nice.

Thanks!

--
Mariano
http://marianopeck.wordpress.com

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Dale Henrichs-3

Re: [Glass] Is there a Smalltalk way to lock a file?

Not aware of a way to do it directly... If you can do it from the shell, then System class>>performOnServer: will be your friend:)

Dale

On Thu, Mar 13, 2014 at 9:14 AM, Mariano Martinez Peck <[hidden email]> wrote:

Hi guys,

Do we have a method to lock a file at the OS level? I searched in image but I cannot find anything. If it would work in gemstone too that would be nice.

Thanks!

--
Mariano
http://marianopeck.wordpress.com

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Richard Sargent

Re: [Glass] Is there a Smalltalk way to lock a file?

Administrator

In reply to this post by Mariano Martinez Peck

Mariano Martinez Peck wrote

Do we have a method to lock a file at the OS level? I searched in image but
I cannot find anything. If it would work in gemstone too that would be nice.

It's not clear what your intention is. Typically, opening a file for write access should prevent any other process from opening it (for write access). I think the semantics of file access are operating system specific. But most OS's should come close to what's defined for Posix, I expect. (Windows maybe not so close.)

James Foster-9

Re: [Glass] Is there a Smalltalk way to lock a file?

In reply to this post by Mariano Martinez Peck

On Mar 13, 2014, at 9:14 AM, Mariano Martinez Peck <[hidden email]> wrote:

Hi guys,

Do we have a method to lock a file at the OS level? I searched in image but I cannot find anything. If it would work in gemstone too that would be nice.

Thanks!

--
Mariano
http://marianopeck.wordpress.com

I was thinking that opening a file for write would be sufficient, but that isn’t what I found (on GS/S 64-bit 3.1.0.5 on Linux):

topaz> login

[03/13/2014 17:12:35.983 PDT]

  gci login: currSession 1 rpc gem processId 28015 OOB keep-alive interval 0

successful login

topaz 1> run

UserGlobals at: #'James1' put: (GsFile openAppendOnServer: 'test').

%

aGsFile

topaz 1> login

[03/13/2014 17:13:36.178 PDT]

  gci login: currSession 2 rpc gem processId 28021 OOB keep-alive interval 0

successful login

topaz 2> run

UserGlobals at: #'James2' put: (GsFile openAppendOnServer: 'test').

%

aGsFile

topaz 2> set session 1

topaz 1> run

James1 nextPutAll: 'This is from session 1'; cr.

%

true

topaz 1> set session 2

topaz 2> run

James2 nextPutAll: 'This is from session 2'; cr.

%

true

topaz 2> run

James2 close.

%

aGsFile

topaz 2> abort

topaz 2> logout

topaz> set session 1

topaz 1> run

James1 close.

%

aGsFile

topaz 1> abort

topaz 1> run

(GsFile openReadOnServer: 'test') contents

%

This is from session 1

This is from session 2

topaz 1> 

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Martin McClure-5

Re: [Glass] Is there a Smalltalk way to lock a file?

On 03/13/2014 05:24 PM, James Foster wrote:

> On Mar 13, 2014, at 9:14 AM, Mariano Martinez Peck
> <[hidden email] <mailto:[hidden email]>> wrote:
>
>> Hi guys,
>>
>> Do we have a method to lock a file at the OS level? I searched in
>> image but I cannot find anything. If it would work in gemstone too
>> that would be nice.
>>
>> Thanks!
>>
>> --
>> Mariano
>> http://marianopeck.wordpress.com
>
> I was thinking that opening a file for write would be sufficient, but
> that isn’t what I found (on GS/S 64-bit 3.1.0.5 on Linux):

The common type of file locking in Linux is advisory, and therefore not
enforced. Locks must be explicitly obtained and checked.

See
http://en.wikipedia.org/wiki/File_locking#In_Unix-like_systems
for more information.

In GemStone/S, a #performOnServer: of flock is probably the way to go,
using the fileDescriptor of the GsFile as an argument.

Regards,

-Martin

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