Trapping a kill command sent to a script and using it to send an EOF to a subprocess before killing Post: 302880587

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Top Forums UNIX for Advanced & Expert Users Trapping a kill command sent to a script and using it to send an EOF to a subprocess before killing Post 302880587 by jim mcnamara on Friday 20th of December 2013 07:13:00 PM

12-20-2013

Registered User

You need a source of active subprocesses. ptree is available in Solaris, for example.
Linux has /proc/[pid]/ppid. pstree uses this to draw ascii "graphics".

So what OS?

The bash trap statement you want: a function + two trap statements

Code:

zap()  # some method of getting all active children/grandchildren, etc. Assume a file
{
    # turn off trap
    trap - SIGTERM 
    # kill the kids
    me=$$
    while read pid
    do
        if [ $$ -ne  $pid ] ; then   # if active kill the process
           kill -0 $pid && kill $pid
        fi
   done < a_file_with_childrens_pids
}

# enable zap
trap ' zap ' SIGTERM

Bash kill builtin also supports using jobs, so you can use the jobs command to list active children - if they do not have descendants.

Notice there is a very small possibility of a race condition when several SIGTERM (default signal for kill) signals are received at once. In that case zap() will not complete.

You need a way to enumerate children. You can remember their pids in an array or a file or some other object maybe.
If one of the children is "extinct", you did not rembmer that, and the pid is being used by some hapless process - then you have problems. Another race condition. Especially if this stuff runs as root. On linux or solaris you can evaluate the correctness of the pid by querying proc or getting the uid. - maybe like what exe is the potential kid running. If root is running zap() and you run, be sure to keep a tight handle on current active descendant processes. Or you could clobber your own payroll job.

Last edited by jim mcnamara; 12-20-2013 at 08:20 PM..

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LEARN ABOUT OPENSOLARIS

mysql_zap

zap(1)								  MySQL database							    zap(1)

NAME

       zap - a perl script used to kill processes

USAGE

       /usr/bin/mysql_zap [-signal] [-?Ift] pattern

SYNOPSIS

       zap [-I|-?]  [-f] [-t]

DESCRIPTION

       zap    supports by executing

       -I|-?  info

       -f     force

       -t     test

NOTE

       If  -f isn't given, ask user for confirmation for each process to kill. If signal isn't given, try first with signal 15 and after that with
       signal 9. If -t is given the processes is only shown on stdout.

SEE ALSO

       isamchk(1), isamlog(1), mysql(1), mysqlaccess(1), mysqladmin(1), mysqld(1), mysqld_multi(1), mysqld_safe(1), mysqldump(1), mysql_fix_privi-
       lege_tables(1), mysqlshow(1), perror(1), replace(1)

       For  more information please refer to the MySQL reference manual, which may already be installed locally and which is also available online
       at http://www.mysql.com/doc/en/

BUGS

       Please refer to http://bugs.mysql.com/ to report bugs.

AUTHOR

       Ver 1.0, distribution 4.0.24 Michael (Monty) Widenius (monty@mysql.com), MySQL AB (http://www.mysql.com/). This software comes with no war-
       ranty.  Manual  page  by L. (Kill-9) Pedersen (kill-9@kill-9.dk), Mercurmedia Data Model Architect / system developer (http://www.mercurme-
       dia.com)

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +--------------------+------------------------------------+
       |  ATTRIBUTE TYPE    |	       ATTRIBUTE VALUE		 |
       +--------------------+------------------------------------+
       |Availability	    | SUNWmysqlr, SUNWmysqlu, SUNWmysqlt |
       +--------------------+------------------------------------+
       |Interface Stability | External				 |
       +--------------------+------------------------------------+
NOTES

       Source for mysql is available on http://opensolaris.org.

MySQL 4.0							 19 December 2000							    zap(1)

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