Perl parsing ps fwaux output

Question

I am trying to figure out children processes of a given parent from ps fwaux (there may very well be a better way to do this). Basically, I have daemons running that may or may not have a child process running at any given time. In another script I want to check if there are any child processes, and if so do something. If not, error out.

ps fwaux|grep will show me the tree, but I'm not exactly sure what to do with it. Any suggestions would be great.

Answer 1

You could parse the results of a call to Proc::ProcessTable:

use Proc::ProcessTable;

my $processes = Proc::ProcessTable->new(enable_ttys => 0);
my @children = grep { $_->cmndline =~ /some_pattern_matching_your_children/ }  @{$processes->table};

# or:
my @children = grep { $_->ppid == $parent_pid } @{$processes->table};

But stepping back to the larger problem of tracking children: instead of grepping the process table, the children should track themselves using pid files. File::Pid can help you with that.

Answer 2

As an update, this is what I ending up doing (in bash ...)

while :
do
        # find parent ids 
        PIDS="`ps -eao bsdtime,pid,command | egrep -v egrep | egrep 'processname' | awk '{print $2}'`"
        count=0
        # loop through ppids and look for children
        for j in ${PIDS}
        do
                #echo "Parent process = $j"
                CPID="`ps -ef | awk '$3 == J {print $2}' J=$j`"
                for i in ${CPID}
                do
                        #echo "Child process = $i"
                        let count++
                done
        done

Then if count > 0, there are child processes.