Bash hacks by example

Prologue

Most of this is very old and was moved here for me to look back at all the wonderfully bad bash hacks I have done over the years. It also serves to show ways to quickly do things even if they are not always right ;)

Proceed with caution !

Simple one-liners

Find out a list of users and connection time

ac -p | sort -k 2 -gr

Quick way to find what processes are using something

find /proc -ls 2>/dev/null | grep $PATH_YOU_WANT_TO_FIND example find /proc -ls 2>/dev/null | grep "/home/vpopmail/domains"

Quick IPTABLES Firewall connections hack. Count | protocol | DESTIP:PORT | RemoteIP

/usr/sbin/iptstate -s | awk '{print $3,$2,$1}'| cut -d: -f1-2 | uniq -c | sort -g

Used this to run a script and then I did some BC math on the numbers to make sure MRTG was correct.

for i in `seq 1 2`; do /usr/sbin/disklatency2; sleep 60;done

• disklatency2

Used this to move a large number of tar.gz files that were the same size

du -s *| grep .tar.gz | while read SIZE NAME; do if [ $SIZE == 4 ]; then mv $NAME backups/; fi; done

Used to quickly see which domains in /var/qmail/control/virtualdomains were a alias

sed s/:/\ \/g < /var/qmail/control/virtualdomains | while read line1 line2; do if [ "$line1" != "$line2" ]; then echo $line1 $line2;fi;done

Wow this is messy. Used this to find domains larger than 25 email accounts.

for i in `ls /usr/local/sites/`;do for d in `find /usr/local/sites/$i/.qmail* | wc -l`;do if [ $d -gt 25 ]; then echo $i >> /root/list4john; fi; done;done

Used this in a SNMP setup for a FS Inode check...messy and non-Posix I believe but it works in RHEL ;)

df -iP | grep / | while read A B C D E F;do echo -e "$A\nINODES\n$B\nIUsed\n$C\nIFree\n$D\nIUse\n$E"; done

Variables in conditionals are easy !

• This shows a negate of all $WHATEVER devices and finds all physical ethernet controllers (not ports!)

lspcioutput=$(lspci 2>/dev/null)
 if [ $(echo "$lspcioutput" | grep -v $WHATEVER| egrep "^[0-9]+\:[0-9]+\.0 Ethernet" | wc -l) -gt 1 ]; then echo "cool stuff";fi

or you can use awk if you dont like the "dual Grep action" above.

lspci | awk '{ if ( $0 ~ /^[0-9]+\:[0-9]+\.0 Ethernet/ && $4 !~ /$WHATEVER/) count++ } END {print count}'

Backgrounding in a for loop

for i in {1..6}; do  /bin/ping -q -s1024 -f web01& done

or

for i in {1..6}; do { /bin/ping -q -s1024 -f web01&}; done

Slightly Longer Hacks

General Sysadmin fluff

• Script to create some email load Mailer_load.sh
• Script to read and format a list of websites in a directory WebsiteList.sh
• MRTG Graph creation using lynx and a for loop graphcreate.sh
• Check disk space and report with a email for each mounted filesystem over set amount diskspace.sh
• courier-authdaemon convert usernames of $domain-$number from .qmail files to MySQL DB (STILL IN DEVELOPMENT) courierauth_convert.sh

MySQL

• Backup all MySQL DBs using gzip mysqlbackup_gzip.sh

DNS (bind)

• quick hack to populate a bind reverse zone file for RFC1918

The "in theory this might be useful" scripts

• Interesting use for the $RANDOM function in bash pop3random.sh
• Listing all the deps for installed RPMs.

for r in $(rpm -qa); do yum -q deplist $r >> /tmp/deplist ; done

Even Longer Hacks

• A hack using incrond and a bash script to scan files automagicly when put in a folder with the SELinux on. autovirus_walkthrough or the bash script autovirus.sh