Author Topic: "Die on signal fifteen" - SIGTERM Unix reference?  (Read 6164 times)

Offline ioncube

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"Die on signal fifteen" - SIGTERM Unix reference?
« on: Sat, 2006-03-04, 16:11:17 »
Hi

Recently discovered Arena, and am an instant fan. After doing a quick search, I had a lyric origin question as I hadn't found the answer.

I was listening to Enemy Without and immersed into the music and what I was doing, when the phrase "I let the child die on signal fifteen" suddenly wafted in my ears and instantly shook me bolt upright and doing an auditory double take. Improbable perhaps, but is this a passing reference to SIGTERM in Unix which would kill a child process, and is indeed, numbered signal 15?

Unix reference or weird coincidence? Enquiring minds would like to know :)

Nick
« Last Edit: Sat, 2006-03-04, 16:13:24 by ioncube »

Offline PH

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #1 on: Sat, 2006-03-04, 17:51:32 »
Improbable perhaps, but is this a passing reference to SIGTERM in Unix which would kill a child process, and is indeed, numbered signal 15?

Unix reference or weird coincidence? Enquiring minds would like to know :)

Nick

I always wondered what the child dying on signal fifteen is about. But what you just said made me wonder even more.

What exactly do you mean by 'SIGTERM in Unix which would kill a child process'? ???

By the way, A VERY WARM welcome to you my friend!
I recently talked about opening a can of new members, but it seems the can opened itself already. ;D

I hope you'll enjoy being in the Shattered Room.

Offline Appelmoes??

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #2 on: Sat, 2006-03-04, 18:15:27 »
By the way, A VERY WARM welcome to you my friend!
Welcome indeed :)

(On the Ayreon board we have a special section where new members can introduce themselves, I think that would be a nice option here too... maybe... perhaps... I think... ;))

Offline ioncube

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #3 on: Sat, 2006-03-04, 19:05:28 »
I always wondered what the child dying on signal fifteen is about. But what you just said made me wonder even more.

What exactly do you mean by 'SIGTERM in Unix which would kill a child process'? ???

By the way, A VERY WARM welcome to you my friend!

Thanks for the welcome and quick replies :)

It's computing terminology; forgive the beginners guide to computing terms if you're reading and know this stuff. I've put in some links to Wikipedia entries.

Unix is an operating system that dates back a few decades, and still going strong in numerous variants such as Linux. An operating system is the main program that runs when a computer starts up, and defines the characteristics of the machine. Windows XP and Apple OS X etc. are other common examples. A process is a term given to part or all of a running program.

In Unix, a signal is a kind of message, and a process can send a signal to another process. A process that starts another process is called the parent, and the spawned process is called the child. Unix defines several signals, each with their own meaning and behaviour. The signals are numbered (everything ultimately comes down to numbers in a computer), and for convenience, they also have names. The signal called SIGTERM is historically number 15, and it tells a process to terminate before it's natural end point, often called killing (that link mentions SIGTERM and 15). A process that stops before its natural end is often said to have died. 

If the lyric does refer to Unix, then I would imagine that the author (Clive Nolan?) must have some knowledge of Unix or have had help from a Unix programmer on that line, along with a chuckle I would imagine :)

Knowing the possible origin, possibly the most intriguing lyric I've come across.

Nick
« Last Edit: Sat, 2006-03-04, 19:11:19 by ioncube »

Offline JJ II

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #4 on: Sat, 2006-03-04, 22:17:51 »
Read the biografy for the origin. It wasn't Clive who came up with it  ;)

Offline jeffMc

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #5 on: Sun, 2006-03-05, 19:50:24 »
Actually a process is a name given to a protected address space, and can be made up of a stack, a heap, and a number of scheduled entities called threads (or just the process, no threads). The process address space is determined byt the layout of page tables, etc. Older operating systems, such as VMS and older Unix, had only processes and therefore they were the scheduled entity. In more modern OS's like Windows NT/2K/XP/Vista and modern Unix varients, the thread is the scheduled entity, but are managed within the process context. Processes allow multiple applications to run, in a scheduled fashion on a given processor, and they are protected from each other, by the memory management hardware of the given processor. Thus if one application faults, its process and associated threads are terminated, but the other applications run unaffected. I could go into scheduling theory and how address spaces are layed out and how systems space and user space are partitioned, but it is all boring. (Hence why I left operating system architecture and development a couple of years back :) )

As far as letting the child die on signal 15, yeah, figured that one out years ago when Visitor came out ;)

Offline Peter

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #6 on: Sun, 2006-03-05, 22:53:24 »
Nice to have so many computer techies in here. I only know SIGHUP and kill -9 as a last resort :)
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Offline ioncube

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #7 on: Sun, 2006-03-12, 12:31:09 »
Actually a process is a name given to a protected address space...

Well, I was sparing the non-computer techs, so was an accurate enough potted version. As you'll know, the address space is not necessarily protected, (it depends on whether the MMU supports the concept), and whilst a process may run within a protected address space, it doesn't need to.  Threaded systems implementation also varies. It may be that the thread is the only scheduled entity, or that a process is the main scheduled entity with threads or coroutines implemented within and by the process. Where it gets really interesting is where you eliminate the OS, putting what is traditionally in an OS into the hardware, with secondary storage connected to the memory subsystem instead of the processor, persistent memory with no need for a filesystem, scheduling in the hardware with zero time context switching to eliminate the scheduler etc.

I think traditional OS design is far from boring though, although having developed one OS, there's no need to write another :)

I read my first computer book, P J Brown's Interactive Compilers that I saw advertised in one of the computer mags, when I was around 15, and for my O level compsci project designed a high level graphics language and wrote a compiler, supporting full expression evaluation, function calls etc. on my BBC-B to turn that into 6502 assembler. Worked well, giving around a 40 to 50 time speedup over equivalent graphics code in basic on the beeb.

The OS came soon after. I was into stage lighting and electronics too, and at Uni in the late 80's designed a twin CPU digital lighting console to rival the strand devices such as Galaxy that were coming out. It had one of those Hitachi 64 pin HD64180 high integration chips on the main board with a display board using a 6502. I didn't have any dev tools, so wrote relocatable assemblers for Z80 and 6502 and a linker in BCPL so I could write modular code (there were many thousands of lines of assembler in the end). There was a windowing system for the video board and multitasking OS for the main board to manage the separate application processes that controlled the console services and scheduling of the lighting events, highly optimised to handle the level calculations for a hundred or so channels with enough resolution and speed. The two boards talked to each other with a display protocol of a synchronous serial link, optimised to offload processing from the main board, it had a mouse, rotary encoder for the "wheel", the usual sliders and led displays to work if the main display failed. All wirewrapped, but with 6Mhz clocks no problem there. A neat wooden case my dad helped me put together finished that off.  Finally, daisychained 6 channel digital dimmers with 6502's.

Far from boring, working all hours in my student flat on top of Asda in Hatfield town center, hacking thousands of lines of assembler in the OS and the rest of it, and with the occasional smoke (literally) from the hardware, it was all really great fun! Highly recommended :)

Anyway, enough off topic stuff.  My Squeezebox3 just finished playing Visitor again; what a cracking album!
« Last Edit: Sun, 2006-03-12, 12:51:47 by ioncube »

Offline jeffMc

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #8 on: Thu, 2006-03-16, 00:54:21 »
I dunno. I'd rather compose music, and go out with women, than write OS's. I think 4 were enough ;)

Offline ioncube

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #9 on: Sun, 2006-03-19, 16:03:09 »
I dunno. I'd rather compose music, and go out with women, than write OS's. I think 4 were enough ;)

lol, agreed. I did all my piano/violin grades before college, but knowing that I'd never be top of the game at music college I went the compsci route instead, but still played fiddle in string quartets and orchestras. The music scene was a great way to meet other arty types and very enjoyable in many ways ;)

Never got into composing though until recently started dabbling. I just tried the Steinberg Grand 2 with my Studiologic 880, and wow! I just love that controller so much, and with decent grand samples, fantastic! :)

Offline keyboardistmatt

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Re: "Die on signal fifteen" - SIGTERM Unix reference?
« Reply #10 on: Thu, 2006-03-23, 19:34:44 »
Never got into composing though until recently started dabbling. I just tried the Steinberg Grand 2 with my Studiologic 880, and wow! I just love that controller so much, and with decent grand samples, fantastic! :)
Rick Wakeman uses a Studiologic 880.  The keyboard action will probably be the best available, because Fatar (the parent company for Studiologic) make the keyboards for Kurzweil synthesizers.

Your description of the Unix system is as exhaustive as my explanation about the Clavia Nord Electro keyboard!
http://shattered-room.net/index.php?topic=269.msg6640#msg6640

Nice to see that people know their stuff! :)

Oh yeah, hello, by the way! ;) *horns*
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