Hi,
could you please provide a hook for non-root users to execute commands
at ip-up/ip-down, like  @reboot of cron provides for machine startup?

The following script is more intended to demonstrate what I mean than
a real example. Its too klugy, and this kind of thing doesn't belong
into crontabs.







#! /bin/bash
SU="su -c"
cd /var/spool/cron/crontabs
# set ulimit here, if you like

# This script runs users' commands at ip-up or ip-down.  I wrote this
# because I feel there is no need to let root control who can fetch
# mail / update a homesite / monitor websites / ...  Commands in a
# user's crontab are executed by /bin/sh, strippind leading '#@@ip-up ',
# output is mailed if there is any. While crontabs may not be the best
# place to put this, at least this script doesn't create still another
# place with auto-executed commands.

# make this suitable for ip-up and ip-down
case "$0" in
    *user-ip-up)   EVENT=ip-up   ;;
    *user-ip-down) EVENT=ip-down ;;
    *)             echo "usage: .*user-ip-(up|down)  read the script" &&
		   exit 4 ;;
esac


for i in [a-zA-Z0-9]* ; {        #primitive "untaint"
    # is there such a user?
    cut -d ':' -f 1  /etc/passwd |egrep "$i" >/dev/null || continue

    # is he allowed to use cron?
    if [ -f /etc/cron.allow ] ; then
	egrep "$i"  /etc/cron.allow >/dev/null ||continue
    fi
    if [ -f /etc/cron.deny -a ! -f /etc/cron.allow ] ; then
	egrep "$i" /etc/cron.deny >/dev/null && continue
    fi

    # is he making use of this feature?
    egrep '^#@@'$EVENT'[ 	]+' "$i" >/dev/null || continue

    # security for temp files
    TMP_EXEC=`tempfile` || exit 5
    TMP_MAIL=`tempfile` || exit 5
    chmod 0700 $TMP_EXEC
    chmod 0600 $TMP_MAIL
    chown "$i" $TMP_EXEC $TMP_MAIL

    # ignore things like "$MAILTO", "$SHELL", environment for now
    # /var is mounted "-o noexec" on my system
    # process commands in background: don't let users wait on another
    (   echo '#! /bin/sh' ;
	cat "$i" |
	sed  -n 's/^#@@'$EVENT'[  ][      ]*\(.*\)/\1/p' ) > $TMP_EXEC

    (   $SU "/bin/sh $TMP_EXEC" "$i" 2>&1 > $TMP_MAIL
	[ -s $TMP_MAIL ] && mail -s "`hostname` $EVENT: `date`" "$i" <$TMP_MAIL
	rm -f $TMP_MAIL $TMP_EXEC )&
    # finished with user
}   # finished with all users

###5user-ip-up
--- Begin /etc/ppp/ip-up.d/0dns-up (modified conffile)
Config file not present or no permissions for access

--- End /etc/ppp/ip-up.d/0dns-up

--- Begin /etc/ppp/ip-down.d/0dns-down (modified conffile)
Config file not present or no permissions for access

--- End /etc/ppp/ip-down.d/0dns-down