How can I quickly find the user's terminal PID in Perl?

Question

The following snippet of code is used to find the PID of a user's terminal, by using ptree and grabbing the third PID from the results it returns. All terminal PID's are stored in a hash with the user's login as the key.

   ## If process is a TEMINAL.
   ## The command ptree is used to get the terminal's process ID.
   ## The user can then use this ID to peek the user's terminal.
   if ($PID =~ /(\w+)\s+(\d+) .+basic/) {
    $user = $1;
    if (open(PTREE, "ptree $2 |")) {
     while ($PTREE = <PTREE>) {
      if ($PTREE =~ /(\d+)\s+-pksh-ksh/) {
       $terminals{$user} = $terminals{$user} . " $1";
       last;
      }
      next;
     }
     close(PTREE);
    }
    next;
   }

Below is a sample ptree execution:

ares./home_atenas/lmcgra> ptree 29064
485   /usr/lib/inet/inetd start
  23054 /usr/sbin/in.telnetd
    23131 -pksh-ksh
      26107 -ksh
        29058 -ksh
          29064 /usr/ob/bin/basic s=61440 pgm=/usr/local/etc/logon -q -nr trans
            412   sybsrvr

I'd like to know if there is a better way to code this. This is the part of the script that takes longest to run.

Note: this code, along with other snippets, are inside a loop and are executed a couple of times.

Answer 1

I think the main problem is that this code is in a loop. You don't need to run ptree and parse the results more than once! You need to figure out a way to run ptree once and put it into a data structure that you can use later. Probably be some kind of simple hash will suffice. You may even be able to just keep around your %terminals hash and keep reusing it.

Some nitpicks...

• Both of your "next" statements seem unnecessary to me... you should be able to just remove them.

• Replace

  $terminals{$user} = $terminals{$user} . " $1";
  

with:

    $terminals{$user} .= " $1";

• Replace the bareword PTREE which you are using as a filehandle with $ptreeF or some such... using barewords became unnecessary for filehandles about 10 years ago :)

• I don't know why your $PID variable is all caps... it could be confusing to readers of your code because it looks like there is something special about that variable, and there isn't.