watch a log file, echo anything it produces into a fifo

gistfile1.sh

#!/bin/bash
search_str="$1"
pipe=/tmp/alert
trap "rm -f $pipe" EXIT

rm -f $pipe
if [[ ! -p $pipe ]]; then
    mkfifo $pipe
fi


watch(){
tail -Fn0 /usr/local/nagios/var/nagios.log  |  \
    grep -i --line-buffered "$search_str" |
     while read line; do
        echo "$line" > $pipe
      done &
}

watch "$@"