Re^3: ***Warning! The above post is wrong in almost every possible way***

in reply to Re^2: ***Warning! The above post is wrong in almost every possible way***
in thread Kill a process in perl windows and proceed only if it killed the process

"For example, on *nix/POSIX the only mechanism I know of, for terminating a running process, is to send it a signal. But signals are maskable, trappable, and ignorable. Are any of them guaranteed to terminate the process? Do you know the answer? I don't. Do you think he does?"

I certainly can't answer for all OSes, nor even all Unix-like OSes, but on Linux, SIGKILL (signal 9) cannot be trapped. SIGKILL is essentially the untrappable version of SIGINT (which is what Ctrl+C tends to send in the terminal).

Also, SIGSTOP cannot be caught, but SIGSTOP doesn't kill a process, it pauses it. SIGSTOP is the untrappable version of SIGTSTP (which is what Ctrl+Z tends to send in the terminal).

Of course, just because a process cannot trap and handle the signal, doesn't mean that the signal is 100% instant and reliable. Signals can fail to work, or take some time to work for other reasons (e.g. bugs, busy CPU, etc).

Aside: If a process is chewing up your CPU and you need to stop it for a while, kill -s STOP <process_number> is a pretty handy facility. When you're happy for it to start chewing again kill -s CONT <process_number> will restart it. The process is unlikely to even notice you paused it.

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

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Re^4: ***Warning! The above post is wrong in almost every possible way***
by BrowserUk (Pope) on Jul 21, 2012 at 14:58 UTC

on Linux, SIGKILL (signal 9) cannot be trapped.... just because a process cannot trap and handle the signal, doesn't mean that the signal is 100% instant and reliable.

Indeed. The Uninterruptible sleep state for example.

you need to stop it for a while, kill -s STOP <process_number> is a pretty handy facility.

Similarly, windows has suspend/resume which I frequently use to pause longing running, CPU intensive tasks when I want to do something else for a while, but don;t want to throw away the work already done.

The only downside is that if you are benchmarking the process, the suspend will affect the timing if you use real-time clocks. Recently, I've moved to using clock-cycle counters for important benchmarking for this reason.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

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Re^3: Warning! The above post is wrong in almost every possible way

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