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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
Old 12-20-2013
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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pure-uploadscript(8)						     Pure-FTPd						      pure-uploadscript(8)

NAME
pure-uploadscript - Automatically run an external program after a successful upload SYNTAX
pure-uploadscript [-p </path/to/pidfile>] [-B] [-g <gid>] [-h] -r <program to run> [-u <uid>] DESCRIPTION
If Pure-FTPd is compiled with --with-uploadscript (default in binary distributions), and if the -o (or --uploadscript) is passed to the server, a named pipe called /var/run/pure-ftpd.upload.pipe is created. You will also notice an important file called /var/run/pure-ftpd.upload.lock, used for locking. After a successful upload, the file name is written to the pipe. pure-uploadscript reads this pipe to automatically run any program or script to process the newly uploaded file. OPTIONS
-B Daemonize the process and fork it in background. -g <gid> Switch the group ID to <gid>. -h or --help Display available options. -r <program to run> Tell what program/script to run. It has to be an absolute filename, the PATH environment variable is ignored. The first argument of that program will be the unquoted name of the newly uploaded file. Environment variables aren't cleared. So don't put sensitive data in them before calling pure-uploadscript if you switch uid. -u <uid> Switch the user ID to <uid>. ENVIRONMENT
When the upload script is run, the name of the newly uploaded file is the first argument passed to the script (referenced as $1 by most shells) . Some environment variables are also filled by useful info about the file. UPLOAD_SIZE The size of the file, in bytes. UPLOAD_PERMS The permissions, as an octal integer. UPLOAD_UID The numerical UID of the owner. UPLOAD_GID The numerical GID of the owner. UPLOAD_USER The login of the owner. UPLOAD_GROUP The group name the files belongs to. UPLOAD_VUSER The full user name, or the virtual user name (127 chars max) . FILES
/var/run/pure-ftpd.upload.pipe /var/run/pure-ftpd.upload.lock /var/run/pure-uploadscript.pid SECURITY
pure-ftpd and pure-uploadscript are trying to limit security implications of such a feature. - The pipe can only be created and opened by root. It must have perms 600, with uid 0, or it will be ignored. - The argument passed to an external program/script is always an exact absolute path name. It doesn't get fooled by chroot()ed environ- ments, and by absolute or relative paths added to the STOR command. - UID and GID are set just after parsing command-line options, and pure-uploadscript never gets back supervisor privileges. - Descriptors to the pipe are never passed to external programs/scripts. So when UID switched, the target user can't mess the pipe. - Only regular files are processed, control characters are rejected, and a header+footer avoid partial file names. - Two external programs/scripts can't run at the same time. Uploads are always processed sequentially, in chronological order. This is to avoid denial-of-services by issuing a lot of simultaneous STOR commands in order to launch a fork bomb on the server. For this reason, your programs shouldn't take a long time to complete (but they can run themselves in background) . EXAMPLES
A sample script could be : #! /bin/sh echo "$1 uploaded" | /usr/bin/mutt -s "New upload : $1" ftpadmin@dom.ai.n Never forget to quote ("variable") all variables in all your shell scripts to avoid security flaws. AUTHORS
Frank DENIS <j at pureftpd dot org> SEE ALSO
ftp(1), pure-ftpd(8) pure-ftpwho(8) pure-mrtginfo(8) pure-uploadscript(8) pure-statsdecode(8) pure-pw(8) pure-quotacheck(8) pure-authd(8) RFC 959, RFC 2228, RFC 2389 and RFC 2428. Pure-FTPd team 1.0.36 pure-uploadscript(8)
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