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December 19, 2015 16:38
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Incremental reading of files that get rotated. If files are being written to it ignores the bytes written since the first `stat` call, avoiding double reads. Fairly untested so far, not even sure if it recognizes that the log rotation was performed. Mileage may vary, feel free to submit fixes.
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#!/bin/bash | |
function usage { | |
echo Usage: $0 logfile.log logfile.log.1 [name] | |
exit | |
} | |
if [ -z $1 ]; then | |
usage | |
fi | |
if [ -z $2 ]; then | |
usage | |
fi | |
LOGNAME=".offset" | |
if [ ! -z "$3" ]; then | |
LOGNAME=".$3" | |
fi | |
LOG_SIZE=`stat -c %s $1` | |
LOG_OFFSET=0 | |
if [ -f "$1$LOGNAME" ]; then | |
LOG_OFFSET=`cat $1$LOGNAME` | |
else | |
# first run, skip all data so far | |
echo $LOG_SIZE > $1$LOGNAME | |
exit | |
fi | |
if (( $LOG_SIZE > $LOG_OFFSET )); then | |
CHANGED=`expr 1 + $LOG_SIZE - $LOG_OFFSET` | |
tail -c +$LOG_OFFSET $1 | head -c $CHANGED | |
else | |
LOG_SIZE2=`stat -c %s $2` | |
if (( $LOG_SIZE2 > $LOG_OFFSET )); then | |
tail -c +$LOG_OFFSET $2 | |
fi | |
cat $1 | head -c $LOG_SIZE | |
fi | |
echo $LOG_SIZE > $1$LOGNAME |
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