Let's start with a simple task. Say we have a load of files in a directory, e.g. null121231.xml, null3049432.xml etc. and we want to remove null from the start of the files' names:
for f in null*; do mv "$f" "${f#null}"; done
Moving onto a little more complex. I wanted to write a script that would backup these files to another machine. I felt it was more logical to trigger this script from the remote machine so I did it this way:
Remote machine: telex
Local machine (where backup is being stored): hossbox
#!/bin/bash
# Off site backup script for live database
#
#
# DATE: 27/08/2009
#################################
# Assign Date variables #
#################################
startTime=`date`
LOGFILE=/home/java/blog_backup_jobs.txt
echo $startTime ": Starting blog backup" >> $LOGFILE
# Ping interval in seconds
PINGINTERVAL=600
numErrors=0
HOST=telex
#### functions ####
function pinghost()
{
ping -c 1 $1 &> /dev/null
if [ $? = 0 ]; then
return 0
else
return 111
fi
}
function notifyAdmin()
{
# email subject
SUBJECT="Blog backup failed, mecca failed to respond for 1 hour"
# Email to?
EMAIL="patrick@localhost"
# Email text/message
EMAILMESSAGE="/home/java/cron/emailmessage.txt"
echo "$HOST has failed to respond for 1 hour. The blog backup script has failed" > $EMAILMESSAGE
# Send email using /bin/mail
/bin/mail -s "$SUBJECT" "$EMAIL" < $EMAILMESSAGE
}
#### Script starts here ####
pinghost $HOST
errorCode=$?
while [ $errorCode -eq 111 ]
do
numErrors=$(( $numErrors + 1 ))
echo "`date +%r`: Ping error $numErrors to $HOST" >> $LOGFILE
if [ $numErrors -eq 6 ]; then
echo "`date +%r`: Couldn't ping $HOST for 1 hour, emailing admin.." >> $LOGFILE
# calling a function to email someone here
notifyAdmin
echo "`date +%r`: mail sent....exiting." >> $LOGFILE
exit 1
else
sleep $PINGINTERVAL
pinghost $HOST
errorCode=$?
fi
done
# If we're here then mecca is up. Now we need to connect and
# check if the blog extraction job is finished
# returns 202 if the pid file exits
# returns 0 if it doesn't
PIDFILE=/home/java/extract_blog.pid
function checkBlogJobFinished()
{
if ssh $HOST 'ls "'$PIDFILE'" >/dev/null'; then
return 202;
else
return 0;
fi
}
checkBlogJobFinished
errorCode=$?
numChecks=0
# time to sleep in seconds, 7200seconds = 2 hours
SLEEPTIME=7200
while [ $errorCode -eq 202 ]
do
numChecks=$(( $numChecks + 1 ))
echo "`date +%r`: Check $numChecks: job still running, going to sleep for $SLEEPTIME seconds" >> $LOGFILE
sleep $SLEEPTIME
checkBlogJobFinished
errorCode=$?
done
# If we're here then the blog job has finished, time to get the blog xml files
########################################
# Backup Site Directory - files #
########################################
# remote blog folder is of format: week{currentWeekNo_currentYear}
remoteBlogFolder=/home/java/extractor/blogs/week`date +%V_%Y`
localBlogFolder=/home/java/backup/mecca/blogs
if [ ! -e $localBlogFolder ]
then
mkdir -p $localBlogFolder
fi
echo "`date +%r`: Starting retreival of $remoteBlogFolder" >> $LOGFILE
rsync -avz -e "ssh -i /home/java/cron/hossbox-rsync-key-java" java@$HOST:$remoteBlogFolder $localBlogFolder
echo "`date +%r`: Ending retreival of $remoteBlogFolder" >> $LOGFILE
currentWeek=`date +%V`
let previousWeek=$currentWeek-1
oldBackupFolder=/home/java/backup/telex/blogs/week$previousWeek
# remove old backup
if [ -e $oldBackupFolder ]
then
rm -rf $oldBackupFolder
fi
endTime=`date`
echo $endTime ": Ending blog backup" >> $LOGFILE
This script sleeps for 2 hours if a blog extraction job is running on the remote machine. It sleeps for 10 minutes if the remote machine isn't responding.
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