Simple bash script to truncate lines from the beginning of a file. Useful for dealing with large log files.

logtruncate

#!/bin/bash 

function log_output {
	logger -p daemon.warning $1
	echo $1
}

function truncate_start {
	FILE_PATH="$1"
	SAVE_LINES=$2
	FILE_LINECOUNT=($(wc -l ($FILE_PATH) | awk '{print $1}'))
	
	if [[ $SAVE_LINES -ge $FILE_LINECOUNT ]]
	then
		> $FILE_PATH
		log_output "$FILE_PATH - file truncated to null"
	
	elif [[ $SAVE_LINES -gt 0 ]]
	then
		NEW_START_LINE=$(($FILE_LINECOUNT-$SAVE_LINES+1))
		sed -ie "1,${NEW_START_LINE}d" $FILE_PATH
		log_output "$FILE_PATH - first $NEW_START_LINE lines removed"
		
	else
		log_output "$FILE_PATH - invalid argument to keep '$SAVE_LINES' lines"
	fi
}

function find_file_matches {
	BASE_PATH="$1"
	FILENAME="$2"
	MIN_FILESIZE=$3
	SAVE_LINES=$4
		
	FILE_LIST=($(find $BASE_PATH -type f -name $FILENAME -size +$MIN_FILESIZE 2>/dev/null))

	for FILE in "${FILE_LIST[@]}"
	do
		truncate_start $FILE $SAVE_LINES
	done
	
}

# Let's look for some common types of logs that should be made smaller
# find_file_matches [base path] [filename] [min filesize]
# brcm-iscsi.log
#find_file_matches "/var/logs" "brcm-iscsi.log" "10M"	
# error_log
#find_file_matches "/home" "error_log" "10M"

find_file_matches "/Users/kelchm/Downloads" "error_log" "1k" "10"

find_file_matches "/Users/kelchm/Downloads" "foo" "1k" "100"