Tails a log until a string is found

tail_log_until_string_found.sh

#!/bin/bash
# Date:         12/28/2016
# Author:       Christopher Rung
# Description:  Tails a log until a (case-insensitive) string is found
# Usage:        ./tail_log_until_string_found.sh [host] [log file] [search term] [timeout]
# Example:      ./tail_log_until_string_found.sh server /var/log/clrung/application.log "finished" 5m
# Exit codes:   0: successful; the search term was found in the log within the specified timeout
#               1: unsuccessful; the search term was not found in the log within the specified timeout

HOST=$1
LOG_FILE=$2
n=3
SEARCH_TERM="${!n}"
TIMEOUT=$4

if [ $# -lt 4 ]; then
	echo "ERROR: insufficient parameters."
	echo "Usage: $0 [host] [log file] [search term] [timeout]"
	exit 1
fi

# adapted from http://superuser.com/a/917112
wait_str() {
	(timeout $TIMEOUT tail -f -n0 "$LOG_FILE" &) | grep -qi "$SEARCH_TERM" && echo -e "\nSUCCESS: \"$SEARCH_TERM\" was found in $LOG_FILE within $TIMEOUT.\n" && exit 0

	echo -e "\nFAILURE: \"$SEARCH_TERM\" was not found in $LOG_FILE within $TIMEOUT.\n"
	exit 1
}

if [ "$HOST" == "localhost" ] ; then
	wait_str "$LOG_FILE" "$SEARCH_TERM" $TIMEOUT
else
	SEARCH_TERM="\"$SEARCH_TERM\""
	ssh -o LogLevel=ERROR ${HOST} "bash -s" < $0 localhost $LOG_FILE $SEARCH_TERM $TIMEOUT
fi