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Opinion: locks, nonblock


This is more a request for opinions than a question.

Last weekend I decided that I'd try to implement a native "shell file 
locking". I have made a patch to bash 3.0.14 just for experimenting:

The patch adds to options: exlock and nonblock.
That was just a test. exlock implements a lock to every file opened by the 
shell (using exec) and nonblock makes O_NONBLOCK'ed operations (including 
the possibly exlock'ed I/O).

My real target while making the patch was the possibility to write a zsh 
module to implement such operations in a native way. Most of these could 
very well be implemented outside the shell while others would have to be 
implemented natively in the environment.

For instance, I have been using lockfile (of procmail) to lock files for 
years. Now I'm wondering if it would not be nicer to have that operation 
natively in my zsh environment.

Some of these operations - like setting a nonblock flag to a fd, or just 
temporarily locking a fd - could help in various ways.

So, the opinions...

Does anyone implemented something like that already? Or else, does anyone 
have specific tricks to achieve similar functionality? I've researched a 
bit and found nothing.

Do you guys think it would be nice to have that functionality implemented 
natively in the shell?

Also, any pointers to implementing that functionality? Would it be better 
designed as a module or natively to the zsh? At first I thought it would 
be nice to write a module implementing something like a "generic file 
descriptior handling" operation.

Are are your opinions on these points?

Felipe Kellermann

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