ru.perl

 
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 From : Alexander P. Russkih                 2:468/75       07 Apr 2004  22:38:24
 To : All
 Subject : Re: блокировак повторного запуска
 -------------------------------------------------------------------------------- 
 

 Michael Spector wrote:
 
 >  YM> pid-файл  - это файл, в который записан process id твоего скрипта. 
 >  YM> Соответственно, можно ещё проверять, что процесс с таким id существует 
 >  YM> (например, командой ps).
 > А лучше делать посылать ему нулевой сигнал и смотреть на exit status.
 
 почитал я тут переписку по сабжу и почему-то подумалось.
 во-первых, речь идет про *nix
 во-вторых, кто мешает для проверки запущен-незапущен использовать командочку 
 lockfile?
 вот выдержка из man-а на нее:
 ===================
 NAME
         lockfile - conditional semaphore-file creator
 
 SYNOPSIS
         lockfile -sleeptime | -r retries |
              -l locktimeout | -s suspend | -!  | -ml | -mu | filename ...
 
 DESCRIPTION
         lockfile  can  be  used to create one or more semaphore files.  If 
 lockfile can't create all the specified files (in the
         specified order), it waits sleeptime (defaults to 8) seconds and 
 retries the last file that  didn't  succeed.   You  can
         specify  the  number  of  retries to do until failure is returned.  If 
 the number of retries is -1 (default, i.e., -r-1)
         lockfile will retry forever.
 
         If the number of retries expires before all files have been created, 
 lockfile returns failure and removes all the  files
         it created up till that point.
 
         Using  lockfile as the condition of a loop in a shell script can be 
 done easily by using the -!  flag to invert the exit
         status.  To prevent infinite loops, failures for any reason other than 
 the lockfile already existing are not inverted to
         success but rather are still returned as failures.
 
         All  flags  can be specified anywhere on the command line, they will 
 be processed when encountered.  The command line is
         simply parsed from left to right.
 
         All files created by lockfile will be read-only, and therefore will 
 have to be removed with rm -f.
 
         If you specify a locktimeout then a lockfile will be removed by force 
 after locktimeout seconds have  passed  since  the
         lockfile  was last modified/created (most likely by some other program 
 that unexpectedly died a long time ago, and hence
         could not clean up any leftover lockfiles).  Lockfile is clock skew 
 immune.  After a lockfile has been removed by force,
         a  suspension  of  suspend seconds (defaults to 16) is taken into 
 account, in order to prevent the inadvertent immediate
         removal of any newly created lockfile by another program (compare 
 SUSPEND in procmail(1)).
 
     Mailbox locks
         If the permissions on the system mail spool directory allow it, or if 
 lockfile is suitably setgid, it will  be  able  to
         lock and unlock your system mailbox by using the options -ml and -mu 
 respectively.
 
 EXAMPLES
         Suppose you want to make sure that access to the file "important" is 
 serialised, i.e., no more than one program or shell
         script should be allowed to access it.  For simplicity's sake, let's 
 suppose that it is a shell script.   In  this  case
         you could solve it like this:
 
                ...
                lockfile important.lock
                ...
                access_"important"_to_your_hearts_content
                ...
                rm -f important.lock
                ...
         Now  if  all the scripts that access "important" follow this 
 guideline, you will be assured that at most one script will
         be executing between the `lockfile' and the `rm' commands.
 ... и т.д.
 ===================
 вот собственно и все, что хотелось сказать :-)
 
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