bash – Page 7 – Ryan Schulze

Script of the day – clean up stale .ssh/known_hosts

August 19, 2010May 13, 2013Ryanbash

This little script takes an IP or hostname as a parameter, and if there is an offending key in the .ssh/known_hosts it removes it and replaces it with the current valid one useful if you are moving/reinstalling a large amount of servers …

#!/bin/bash
#===============================================================================
# FILE: ssh-cleankey.sh
# USAGE: ./ssh-cleankey.sh 
#
# DESCRIPTION: deletes stale ssh known_hosts entries
#===============================================================================

# true or fasle
VERBOSE=false

#=== Exit codes ================================================================
# 1 - Not a valid IP or not reachable
#===============================================================================

#=== FUNCTION ================================================================
# NAME: print_help
# DESCRIPTION: Prints help and exits
#===============================================================================
print_help() { #{{{
echo "Usage: `basename $0` "
echo ""
echo "e.g. ./`basename $0` 1.2.3.4"
echo ""
exit 0
} #}}}

if [[ $# -eq 1 ]]
then
HOST="${1}"
else
print_help
fi

ping -w1 -c1 $HOST &gt;/dev/null 2&gt;&amp;1
if [[ $? != 0 ]]
then
$VERBOSE &amp;&amp; echo "ERROR: $HOST is either not a valid IP/hostname, or is not reachable via ping"
exit 1
fi

Check=$(ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true 2&gt;&amp;1|grep -c "Offending key")
if [[ $Check -gt 0 ]]
then
$VERBOSE &amp;&amp; echo "$HOST is stale, updating known_hosts"
ssh-keygen -R $HOST &gt;/dev/null 2&gt;&amp;1
ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true &gt;/dev/null 2&gt;&amp;1
else
$VERBOSE &amp;&amp; echo "$HOST is OK"
fi

exit 0

#!/bin/bash

#===============================================================================

# FILE: ssh-cleankey.sh

# USAGE: ./ssh-cleankey.sh

# DESCRIPTION: deletes stale ssh known_hosts entries

#===============================================================================

# true or fasle

VERBOSE=false

#=== Exit codes ================================================================

# 1 - Not a valid IP or not reachable

#===============================================================================

#=== FUNCTION ================================================================

# NAME: print_help

# DESCRIPTION: Prints help and exits

#===============================================================================

print_help() { #{{{

echo "Usage: `basename $0` "

echo ""

echo "e.g. ./`basename $0` 1.2.3.4"

echo ""

exit 0

} #}}}

if [[ $# -eq 1 ]]

then

HOST="${1}"

else

print_help

ping -w1 -c1 $HOST >/dev/null 2>&1

if [[ $? != 0 ]]

then

$VERBOSE && echo "ERROR: $HOST is either not a valid IP/hostname, or is not reachable via ping"

exit 1

Check=$(ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true 2>&1|grep -c "Offending key")

if [[ $Check -gt 0 ]]

then

$VERBOSE && echo "$HOST is stale, updating known_hosts"

ssh-keygen -R $HOST >/dev/null 2>&1

ssh -o connecttimeout=10 -o stricthostkeychecking=no $HOST true >/dev/null 2>&1

else

$VERBOSE && echo "$HOST is OK"

exit 0

Checking a list of IPs against RBL

August 10, 2010March 12, 2011Ryanbash

This is more a reminder to myself than anything else … this is small snippet that takes a list of IPs and does a whois on all that aren’t in a RBL

Lets say we have al list of IPs in a file “iplist.txt”:
12.172.121.171 24.149.208.68 38.105.100.9 58.185.207.86 61.201.51.66 64.78.164.169

Snippet that checks the IPs (can of course be easily changed to check IPs that are IN a RBL)

for ip in $(cat iplist.txt)
do
test $(/usr/bin/rblcheck -qm ${ip}) &amp;&amp; continue || clear
whois $ip
printf "###########################\n##### %15s #####\n###########################\n" "${ip}"
read
done

for ip in $(cat iplist.txt)

test $(/usr/bin/rblcheck -qm ${ip}) && continue || clear

whois $ip

printf "###########################\n##### %15s #####\n###########################\n" "${ip}"

read

done

bash: using the content of a variable as variable name

August 5, 2010March 12, 2011Ryanbash

Since the implementation of Arrays in Bash is somewhat lacking compared to higher level programming languages (only one-dimensional), and hash lists require a bit of work to set up, you may run into a situation where you have a small list of key/value pairs that are both variable and you need to store.
There are various solutions for the problem, e.g. creating two arrays (one for the keys, one for the values, and combining them by using the same index values for the entries), or using the functions from the link above to build a hash list. For me the easiest way to solve the problem, if I only have a few variables and don’t want to bloat the code, is to (mis)use declare. declare is intended for setting the type of a variable (constant, array, integer,…), but has the nice side affect that you can use variables in the key name, and you can set the value of the variable.

usage:
declare ${Key}=${Value}

Example:
$File_Config is variable holding the name of a configfile, the content of the file could look like this:
foo:one bar:three foobar:bignumber

Snippet:

if [[ -e "${File_Config}" ]]
then
while read line
do
Key="${line%%:*}" # chop off everything after the first :
Value="${line#*:}" # chop off everything before the first :
Value="$(echo ${Value}|sed 's#^ +##g;s# +$##g')" # chop off any excess whitespace
if [[ "${Key}" != "" &amp;&amp; "${Value}" != "" ]] # only continue if we have something to do
then
declare Configuration_${Key}="${Value}"
fi
done &lt; "${File_Config}"
fi

if [[ -e "${File_Config}" ]]

then

while read line

Key="${line%%:*}" # chop off everything after the first :

Value="${line#*:}" # chop off everything before the first :

Value="$(echo ${Value}|sed 's#^ +##g;s# +$##g')" # chop off any excess whitespace

if [[ "${Key}" != "" && "${Value}" != "" ]] # only continue if we have something to do

then

declare Configuration_${Key}="${Value}"

done < "${File_Config}"

after the snippet has read the configfile, you can use $Configuration_foo, $Configuration_bar and $Configuration_foobar in your script. The keynames could also have came from a mysql query, array, command line args, …

Mythtv and IR Blaster

January 24, 2010March 12, 2011Ryan2 Commentsbash, ir blaster, MythTV

We use a set-top-box as the video source for mythtv. And while this works perfectly fine, we have to manually make sure the right channel is set for what mythtv wants to record. This can turn out to being a pain at time, especially when multiple things are planned to be recorded on different channels. So I went and ordered a IR transmitter from irblaster.info to give mythtv the possibility to change channels itself.

Since a bunch of the infos I found online were a bit out dated, here are a few tips for anyone using current versions of the software (I’ve got mythtv-backend 0.22 and lirc 0.8.4a running on a mythbuntu based system when I wrote this)

Hardware is easy to set up, just plug it into a free serial port.
1st we will head over to http://lirc.sourceforge.net/remotes/ and grab the file for our reciever set-top-box if we don’t already have them.
Then go edit /etc/lirc/hardware.conf and add the transmitter settings, these were mine:
TRANSMITTER="Skymaster_XL10" TRANSMITTER_MODULES="lirc_dev lirc_serial" TRANSMITTER_DRIVER="" TRANSMITTER_DEVICE="/dev/lirc1" TRANSMITTER_LIRCD_CONF="skymaster/XL10" TRANSMITTER_LIRCD_ARGS=""
now include the reciever settings to /etc/lirc/lircd.conf
I edited my /etc/init.d/lirc to execute the following line before starting the daemon (was needed to ensure the lirc_serial module can be loaded):
/bin/setserial /dev/ttyS0 uart none
Restart lircd and you can then start testing if transmitting codes work with irsend works. here is a little wrapper script I wrote around irsend for mythtv to use. You may have to twiddle around with the sleeps and change the $Remote to your reciever. If the sleeps are too long (-> the script takes to long to finish switching channels), then mythtv will timeout and not display live tv.

#!/bin/bash

Remote="Skymaster_XL10"

send="irsend -d /dev/lircd1 SEND_ONCE"

if [[ "$(echo $1|grep -c "^[0-9]")" = "0" ]]
then # non-numeric command
$send $Remote $1
else # numeric
for digit in $(echo $1 | sed -e 's/./&amp; /g'); do
$send $Remote $digit
sleep 1.5
done
fi
sleep 2

#!/bin/bash

Remote="Skymaster_XL10"

send="irsend -d /dev/lircd1 SEND_ONCE"

if [[ "$(echo $1|grep -c "^[0-9]")" = "0" ]]

then # non-numeric command

$send $Remote $1

else # numeric

for digit in $(echo $1 | sed -e 's/./& /g'); do

$send $Remote $digit

sleep 1.5

done

sleep 2

If everything is working fine, then go ahead and tell mythtv to use the script to change channels. This is done in the tuner card setup of mythtv-backend (mythtv-setup).

bash scripting … switching into directory of the script

November 23, 2009March 12, 2011Ryanbash, readlink, snippet

Sometimes it is useful to switch into the directory of the script e.g. when we need to call or include further files and don’t want to go through the hassle of searching for the script in the file system. Especially when symlinks are involved everything get a bit more interesting. This little snippet switches into the directory of the script, using readlink to dereference symlinks if the script is called via a symlink.

## a small snippet to switch into script directory
SCRIPTDIR=${0}
if [[ -L ${SCRIPTDIR} ]]
then
# dereference the symlink
SCRIPTDIR="$(readlink -e ${0})"
fi
# chop off the scriptname and switch into the directory
cd ${SCRIPTDIR%/*}

## a small snippet to switch into script directory

SCRIPTDIR=${0}

if [[ -L ${SCRIPTDIR} ]]

then

# dereference the symlink

SCRIPTDIR="$(readlink -e ${0})"

# chop off the scriptname and switch into the directory

cd ${SCRIPTDIR%/*}