updated ports compile question

hi is there a command that will only compile and install preinstalled ports just ones that have been updated. i have done a: portsnap fetch and a portsnap update but i dont want to spend hours doing a make deinstall and make install if there is one command that checks all ports for a new release, then compiles them and then installs them. I know i could use commands to install binaries, but i prefer compiling.
ports-mgt/portmaster is what you need. After you update the ports tree, postmaster can check to see what is updated by looking at what you have installed. Works great. Read the docs for switches.

EDIT: I should have included some basic switches, sorry. portmaster -a will check all installed ports and update as necessary. You can use this little script I put together on advice from wblock (http://www.wonkity.com/~wblock/docs/html/portupgrade.html). Adjust your shell as necessary:

#! /bin/tcsh

portmaster -L --index-only | egrep '(ew|ort) version|total install'
echo -n "Last update: "
date -r `pkg query %t | sort | tail -n1` "+%Y%m%d"

I just called the script "checkupdate" and put it in root's $HOME and $PATH so it can be easily run after I update the ports tree.
I have run portmaster -af however it stops at pkgconf-1.1.1 with the error, has known vulnerabilities, I know i can just cd into the port directory and do a make DISABLE_VULNERABILITIES=yes install however i dont want to do this for every port that has this flag, will take me ages. I tried adding the -f flag to portmaster however it still stops at known vulnerabilities. Is there a switch in portmaster that i can use that will automatically build and install src with the vulnerabilities flag? or do i have to do this manually and then run portmaster again?
so far every port listed after running portmaster -a is flagged vulnerable, and i have to manually reinstall it. would be great if there is an update to portmaster that would automate applying the
part of the portmaster options.
After doing a portmaster -a I also keep getting
 echo: write error on stdout
but it keeps continuing.