Using file locks

TODO.

• This page has to be still made. Here follows info to do it provided by Dave (see mailing 23-24-Sep-2021)
• See class: UnixProcessFileLockTestCase
• See class: OSFileLock

File locking is done with posix advisory file locking, as describe in the
man(2) flock man page https://man7.org/linux/man-pages/man2/fcntl.2.html

The necessary primitives are in all of the unix VMs, and are implemented
in the UnixOSProcessPlugin. The plugin source is maintained at
http://www.squeaksource.com/OSProcessPlugin.

I am attaching a copy of the three primitive methods so you can
see what they are doing. These are Smalltalk methods in the plugin
that are translated to C code. You can find the generated C code
for these methods somewhere in the plugin code at
http://squeakvm.org/cgi-bin/viewvc.cgi/squeak/trunk/src/plugins/UnixOSProcessPlugin/UnixOSProcessPlugin.c?revision=3807&view=markup

The methods in package OSProcess make use of these primitives to implement
file locking in Squeak/Cuis, and the unit tests that I referenced show how
it works in the image. UnixOSProcessAccessor provides the direct interface
to the primitives (see category 'file locking'), and OSFileLock and
OSFileRegionLock represent locks on files or regions within a file.