Re: singleton for script with shebang
On Sat, Jan 3, 2015 at 10:09 PM, Bradley b...@customweather.com wrote: On Jan 3, 27 Heisei, at 11:21 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 8:53 PM, Bradley Asztalos b...@customweather.com wrote: On Fri, Jan 2, 2015 at 7:35 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 10:51 AM, Bradley Asztalos b...@customweather.com wrote: : Does --semaphoretimeout 0 mean never give up? Yes: Just as if the option had not been given. If so then -0 could mean give up immediately. -0 = 0, so no. It is implemented in the git version. : So did you provide for a way to give up immediately if sem cannot be acquired immediately? As mentioned, no. If you feel that is very important, please provide a situation where waiting 1 sec for the semaphore before giving up is much worse than waiting 0.2 sec (which is more or less the time it takes to run sem). I could not find a situation in which that extra second made a huge difference. On the contrary I can easily find situations where giving up immediately is less useful than trying for just a second. /Ole
Re: singleton for script with shebang
Ole, RobberA is robbing a bank and posts her accomplice, RobberB, outside the door to keep watch. Independently, RobberC arrives on the scene to rob the bank as well, noticing that the bank is being robbed, she takes off and vows to give up her life of crime. Compare: RobberAB finish their hard days work and leave, when RobberC arrives, .2s later, to Rob a bank that has no money, three dead clerks, a screaming child and cops on their way. RobberC gets hanged for murder. Compare: RobberAB finish their hard days work and leave, when RobberC arrives, 1s later, and notices the bank security guard coming out the door in pursuit of RobberAB. RobberC robs a different bank. The case I was differentiating was between 0 !0 where actionable information is held by the mutex or semaphore itself, and no other variables are required. Obviously in the difference between .2 and 1 is not contained within the semaphore but in some other time variable. With that said, I have no intention of robbing a bank, at least in the foreseeable future, and the question from my side at least was pure pedantry. I withdraw the question ;) Thanks again for your great work, and--just as importantly--careful oversight of this forum. Bradley On Sun, Jan 4, 2015 at 6:26 AM, Ole Tange o...@tange.dk wrote: On Sat, Jan 3, 2015 at 10:09 PM, Bradley b...@customweather.com wrote: On Jan 3, 27 Heisei, at 11:21 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 8:53 PM, Bradley Asztalos b...@customweather.com wrote: On Fri, Jan 2, 2015 at 7:35 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 10:51 AM, Bradley Asztalos b...@customweather.com wrote: : Does --semaphoretimeout 0 mean never give up? Yes: Just as if the option had not been given. If so then -0 could mean give up immediately. -0 = 0, so no. It is implemented in the git version. : So did you provide for a way to give up immediately if sem cannot be acquired immediately? As mentioned, no. If you feel that is very important, please provide a situation where waiting 1 sec for the semaphore before giving up is much worse than waiting 0.2 sec (which is more or less the time it takes to run sem). I could not find a situation in which that extra second made a huge difference. On the contrary I can easily find situations where giving up immediately is less useful than trying for just a second. /Ole
Re: singleton for script with shebang
Ole, No, I did not say anything about Shlomi being right, just that you are clever, in the good sense. To me it is great to be able to use shebang, and it is not overly clever at all, in the bad sense. I often use the /usr/bin/timeout command and parallel + a command + arguments in crontab entries and other shell scripts and that gets unwieldy, so it is rather nice to be able to use shebang to encapsulate at least the parallel part of the command line. Cheers, Bradley On Fri, Jan 2, 2015 at 1:55 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 8:14 AM, Shlomi Fish shlo...@shlomifish.org wrote: On Thu, 1 Jan 2015 13:54:57 -0800 Bradley Asztalos b...@customweather.com wrote: : [... shebang ...] parallel is written in Perl 5 and uses «#!/usr/bin/perl» or whatever as a shebang. As a result it cannot be itself used as a she-bang processor. So why is Shlomi right, when it is clearly possible to use GNU Parallel as shebang program? It is because on some UNIX systems this is actually true. On FreeBSD you need to do: #!/usr/bin/env -S parallel --shebang-wrap ... On other UNIXes there is no work around. Furthermore, I should note that in programming, it is a good idea to stick to the https://en.wikipedia.org/wiki/KISS_principle and not try to be as clever as possible. Sometimes the code is simpler if GNU Parallel is put in the shebang line. But it does carry some limitations. The length of the shebang line is quite limited on many systems, and often the systems will simply chop it off without any warning. See http://www.in-ulm.de/~mascheck/various/shebang/#length /Ole
Re: singleton for script with shebang
Thanks for the reply, see ole's clever response On Jan 1, 27 Heisei, at 11:14 PM, Shlomi Fish shlo...@shlomifish.org wrote: Hi Bradley, On Thu, 1 Jan 2015 13:54:57 -0800 Bradley Asztalos b...@customweather.com wrote: I have a simple script, foo.sh:: #!/bin/bash echo start $$ sleep 10 echo end $$ I can run make sure this runs as a singleton with sem --fg -u --id lock_id ./foo.sh But I'm wondering if it is possible to use shebang in this context as in: ---singleton.sh- #!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id echo start $$ sleep 10 echo end $$ - parallel is written in Perl 5 and uses «#!/usr/bin/perl» or whatever as a shebang. As a result it cannot be itself used as a she-bang processor. Furthermore, I should note that in programming, it is a good idea to stick to the https://en.wikipedia.org/wiki/KISS_principle and not try to be as clever as possible. Hope it helps. Regards, Shlomi Fish This does not work. Any ideas here? Bradley -- - Shlomi Fish http://www.shlomifish.org/ The Human Hacking Field Guide - http://shlom.in/hhfg A kid always wishes they were older until they are 18. Afterwards, they always wish they were younger. Please reply to list if it's a mailing list post - http://shlom.in/reply .
Re: singleton for script with shebang
Agreed Doh! On Jan 2, 27 Heisei, at 12:48 AM, Ole Tange o...@tange.dk wrote: On Thu, Jan 1, 2015 at 10:54 PM, Bradley Asztalos b...@customweather.com wrote: But I'm wondering if it is possible to use shebang in this context as in: It is. ---singleton.sh- #!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id echo start $$ sleep 10 echo end $$ - This does not work. Any ideas here? You are going to say 'Doh'. /bin/bash is not an argument for --shebang-wrap. It is the command you want to be run. Also --semaphore --fg -u --id are not options for bash. Swap them around and you are good: #!/opt/local/bin/parallel --shebang-wrap --semaphore --fg -u --id lock_id /bin/bash (Here is where you say 'Doh'). /Ole
Re: singleton for script with shebang
On Thu, Jan 1, 2015 at 10:54 PM, Bradley Asztalos b...@customweather.com wrote: But I'm wondering if it is possible to use shebang in this context as in: It is. ---singleton.sh- #!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id echo start $$ sleep 10 echo end $$ - This does not work. Any ideas here? You are going to say 'Doh'. /bin/bash is not an argument for --shebang-wrap. It is the command you want to be run. Also --semaphore --fg -u --id are not options for bash. Swap them around and you are good: #!/opt/local/bin/parallel --shebang-wrap --semaphore --fg -u --id lock_id /bin/bash (Here is where you say 'Doh'). /Ole
Re: singleton for script with shebang
Ole, No problem, I realized that it was rhetorical after I wrote the response. Cheers Shlomi and Ole and thank you for the help. Cheers, Bradley On Fri, Jan 2, 2015 at 2:15 AM, Ole Tange o...@tange.dk wrote: On Fri, Jan 2, 2015 at 11:07 AM, Bradley Asztalos b...@customweather.com wrote: No, I did not say anything about Shlomi being right, That was me asking a rhetorical question. I should stop doing that, as that is easy to misunderstand in writing. I should instead have written: Slomi is right in certain circumstances. /Ole
Re: singleton for script with shebang
Hi Bradley, On Thu, 1 Jan 2015 13:54:57 -0800 Bradley Asztalos b...@customweather.com wrote: I have a simple script, foo.sh:: #!/bin/bash echo start $$ sleep 10 echo end $$ I can run make sure this runs as a singleton with sem --fg -u --id lock_id ./foo.sh But I'm wondering if it is possible to use shebang in this context as in: ---singleton.sh- #!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id echo start $$ sleep 10 echo end $$ - parallel is written in Perl 5 and uses «#!/usr/bin/perl» or whatever as a shebang. As a result it cannot be itself used as a she-bang processor. Furthermore, I should note that in programming, it is a good idea to stick to the https://en.wikipedia.org/wiki/KISS_principle and not try to be as clever as possible. Hope it helps. Regards, Shlomi Fish This does not work. Any ideas here? Bradley -- - Shlomi Fish http://www.shlomifish.org/ The Human Hacking Field Guide - http://shlom.in/hhfg A kid always wishes they were older until they are 18. Afterwards, they always wish they were younger. Please reply to list if it's a mailing list post - http://shlom.in/reply .
singleton for script with shebang
I have a simple script, foo.sh:: #!/bin/bash echo start $$ sleep 10 echo end $$ I can run make sure this runs as a singleton with sem --fg -u --id lock_id ./foo.sh But I'm wondering if it is possible to use shebang in this context as in: ---singleton.sh- #!/opt/local/bin/parallel --shebang-wrap /bin/bash --semaphore --fg -u --id lock_id echo start $$ sleep 10 echo end $$ - This does not work. Any ideas here? Bradley
