Re: [fpc-devel] How to use fpFlock?
flock in Linux (at least) is blocking by default unless passed with specific parameter. You can try also to create a mutex that only when removed you will access the procedure/function that try to write to the file, and the process that created the mutex is the only one that can write to that file. You of course remove it when you closed the file. Just an idea... Ido On Fri, May 2, 2008 at 5:35 AM, amir [EMAIL PROTECTED] wrote: Hi, I have many process wanting to write in a file. Each process is going to open the file as a writeonly (using Assignfile and rewrite or fpOpen with o_WrOnly). But there is a risk that two processes simultaneously trying to write a message in the file. I want to use fpflock to avoid this. Is it possible? What I done is something like this: AssignFile (OutputFile, FileName); fpflock (OutputFile, LOCK_EX); Rewrite (OutputFile); ... The description of fpFlock does not say anything about the default behavior of fpFlock (Is it blocking?). What I saw told me that it is not blocking. Is it the correct way of using fpFlock? ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel -- http://ik.homelinux.org/ ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
Re: [fpc-devel] How to use fpFlock?
So what wrong is with the following code?
When running two instance of this program, *both* print After Flock
and wait for an input?
uses
Unix;
var
InputFile: TextFile;
begin
AssignFile (InputFile, 'Lock.txt');
WriteLn ('Before Flock');
Flush (Output);
Fpflock (InputFile, LOCK_SH);
WriteLn ('After Flock');
Flush (Output);
Reset (InputFile);
ReadLn;
CloseFile (InputFile);
end.
ik wrote:
flock in Linux (at least) is blocking by default unless passed with
specific parameter.
You can try also to create a mutex that only when removed you will
access the procedure/function that try to write to the file, and the
process that created the mutex is the only one that can write to that
file.
You of course remove it when you closed the file.
Just an idea...
Ido
On Fri, May 2, 2008 at 5:35 AM, amir [EMAIL PROTECTED] wrote:
Hi,
I have many process wanting to write in a file. Each process is going to
open the file as a writeonly (using Assignfile and rewrite or fpOpen with
o_WrOnly). But there is a risk that two processes simultaneously trying to
write a message in the file. I want to use fpflock to avoid this. Is it
possible? What I done is something like this:
AssignFile (OutputFile, FileName);
fpflock (OutputFile, LOCK_EX);
Rewrite (OutputFile);
...
The description of fpFlock does not say anything about the default
behavior of fpFlock (Is it blocking?). What I saw told me that it is not
blocking.
Is it the correct way of using fpFlock?
___
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Re: [fpc-devel] How to use fpFlock?
You should use LOCK_EX instead (exclusive lock rather then shared lock).
From the man file (man 2 flock):
LOCK_SH Place a shared lock. More than one process
may hold a shared lock for a given file at a given time.
LOCK_EX Place an exclusive lock. Only one process may
hold an exclusive lock for a given file at a given time.
LOCK_UN Remove an existing lock held by this process.
Ido
On Tue, May 6, 2008 at 9:38 AM, amir [EMAIL PROTECTED] wrote:
So what wrong is with the following code?
When running two instance of this program, *both* print After Flock and
wait for an input?
uses
Unix;
var
InputFile: TextFile;
begin
AssignFile (InputFile, 'Lock.txt');
WriteLn ('Before Flock');
Flush (Output);
Fpflock (InputFile, LOCK_SH);
WriteLn ('After Flock');
Flush (Output);
Reset (InputFile);
ReadLn;
CloseFile (InputFile);
end.
ik wrote:
flock in Linux (at least) is blocking by default unless passed with
specific parameter.
You can try also to create a mutex that only when removed you will
access the procedure/function that try to write to the file, and the
process that created the mutex is the only one that can write to that
file.
You of course remove it when you closed the file.
Just an idea...
Ido
On Fri, May 2, 2008 at 5:35 AM, amir [EMAIL PROTECTED] wrote:
Hi,
I have many process wanting to write in a file. Each process is going
to
open the file as a writeonly (using Assignfile and rewrite or fpOpen
with
o_WrOnly). But there is a risk that two processes simultaneously trying
to
write a message in the file. I want to use fpflock to avoid this. Is it
possible? What I done is something like this:
AssignFile (OutputFile, FileName);
fpflock (OutputFile, LOCK_EX);
Rewrite (OutputFile);
...
The description of fpFlock does not say anything about the default
behavior of fpFlock (Is it blocking?). What I saw told me that it is not
blocking.
Is it the correct way of using fpFlock?
___
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___
fpc-devel maillist - fpc-devel@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-devel
--
http://ik.homelinux.org/
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Re: [fpc-devel] How to use fpFlock?
I have tried both of them (LOCK_SH and LOCK_EX). But the result was the
same.
ik wrote:
You should use LOCK_EX instead (exclusive lock rather then shared lock).
From the man file (man 2 flock):
LOCK_SH Place a shared lock. More than one process
may hold a shared lock for a given file at a given time.
LOCK_EX Place an exclusive lock. Only one process may
hold an exclusive lock for a given file at a given time.
LOCK_UN Remove an existing lock held by this process.
Ido
On Tue, May 6, 2008 at 9:38 AM, amir [EMAIL PROTECTED] wrote:
So what wrong is with the following code?
When running two instance of this program, *both* print After Flock and
wait for an input?
uses
Unix;
var
InputFile: TextFile;
begin
AssignFile (InputFile, 'Lock.txt');
WriteLn ('Before Flock');
Flush (Output);
Fpflock (InputFile, LOCK_SH);
WriteLn ('After Flock');
Flush (Output);
Reset (InputFile);
ReadLn;
CloseFile (InputFile);
end.
ik wrote:
flock in Linux (at least) is blocking by default unless passed with
specific parameter.
You can try also to create a mutex that only when removed you will
access the procedure/function that try to write to the file, and the
process that created the mutex is the only one that can write to that
file.
You of course remove it when you closed the file.
Just an idea...
Ido
On Fri, May 2, 2008 at 5:35 AM, amir [EMAIL PROTECTED] wrote:
Hi,
I have many process wanting to write in a file. Each process is going
to
open the file as a writeonly (using Assignfile and rewrite or fpOpen
with
o_WrOnly). But there is a risk that two processes simultaneously trying
to
write a message in the file. I want to use fpflock to avoid this. Is it
possible? What I done is something like this:
AssignFile (OutputFile, FileName);
fpflock (OutputFile, LOCK_EX);
Rewrite (OutputFile);
...
The description of fpFlock does not say anything about the default
behavior of fpFlock (Is it blocking?). What I saw told me that it is not
blocking.
Is it the correct way of using fpFlock?
___
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___
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[fpc-devel] How to use fpFlock?
Hi, I have many process wanting to write in a file. Each process is going to open the file as a writeonly (using Assignfile and rewrite or fpOpen with o_WrOnly). But there is a risk that two processes simultaneously trying to write a message in the file. I want to use fpflock to avoid this. Is it possible? What I done is something like this: AssignFile (OutputFile, FileName); fpflock (OutputFile, LOCK_EX); Rewrite (OutputFile); ... The description of fpFlock does not say anything about the default behavior of fpFlock (Is it blocking?). What I saw told me that it is not blocking. Is it the correct way of using fpFlock? ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-devel
