Bash Loop Examples

For i in 1-100 do

Basically count to 100 and perform an operation each time i increases.

for ((i=1; i<=100;i++))
do 
  echo $i
done

for loop 1 liner

for ((i=1; i<=100;i++)) do echo $i ; done

While true (Execute forever)

Handy if you just want a script to run and repeat the same thing over and over again. Doesn't stop till you kill it.

while true
do
  echo "Repeat till infinity"
  sleep 1
done

While command is true

The following will execute the loop as long as the command in the () returns true. Once it returns false, it'll stop the loop

while (fping incredigeek.com | grep alive); 
do
  echo alive
  sleep 1
done

Bash array example

#!/bin/bash
array=(one two three)
echo "Printing first object in array."  #Replace 0 with the place number of the array item
echo ${array[0]}

echo ""

echo "Whole array"
echo ${array[*]} 

echo "" 

echo "Array indexes" 
echo ${!array[*]}

Output

Printing first object in array. 
one

Whole array
one two three

Array indexes
0 1 2

https://www.linuxjournal.com/content/bash-arrays

Linux night light script

The following script let you turn your screen brightness up/down, but also adjust the color for night time.

Copy and paste code below in a nightlight.sh file

chmod +x nightlight.sh

and run

./nightlight.sh on .5

Code:

#!/bin/sh
export DISPLAY=$(w $(id -un) | awk 'NF > 7 && $2 ~ /tty[0-9]+/ {print $3; exit}')
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

display=`xrandr | grep "\ connected" | cut -d" " -f1`
brightness="$2"
# Check if brightness was specified.  If not, set screen to 50% brightness
if (echo $2 | grep [0-9]);then
         brightness="$2"
elif (echo $1 | grep -q help);then
         echo "############"
else
         brightness=".5"
         echo "Brightness variable not set, setting to fallback of 50%"
fi
night_mode() {
   for disp in ${display}; do
     xrandr --output $disp --gamma $1 --brightness ${brightness}
  done }
# auto is for future development
# auto() {
# The idea behind auto is to setup something that can pull the actual sunrise/sunset times then automatically adjust the display.
# Ideally there would be an algorithm so it does it slowly over a period of time, say slightly change the color over 30 minutes.
# until the desired color limit is reached
#
# curl sunrise-sunset.com/timezone/time
# if (time > sunset && colorTemp != colorTempMin); then
# set color to current temp-1
# elif (time > sunrise && colorTemp != colorTempMax); then);
# set to full brightness and temp
# else
# unable to parse, skipping.
# fi
#}
 
help() {
echo " Help for nightmode script.  
How to run script
./nightmode.sh on/off brightness
Examples: 
Turn nightmode on and set screen brightness to 75%
./nightmode.sh on .75
Turn night mode off and set screen brightness to 100%
./nightmode.sh off 1
"
}
case $1 in
  off) night_mode 1:1:1 1.0 ;;
  help) help ;;
  auto) auto ;;
  *) night_mode 1:1:0.5 ;;
esac

Setup in crontab to automatically trigger when it gets night or morning

* 21 * * * ~/nightlight.sh on .5  # Turn on at night
* 7 * * * ~/nightlight.sh off 1  # Turn off in the morning

wget multiple links with random access times

Create a file “list.txt” that contains all the URLs you want to download and launch the following command

for i in cat list.txt ; do wget ${i} && sleep $(( ( RANDOM % 120 ) +1 )) ; done

It’ll now run and after each link will wait a random amount of time up to 120 seconds before downloading the next link. Change the number as needed.

Bash random sleep timer

Change the 10 to however many seconds you need or want.

echo $(( ( RANDOM % 10 ) +1 ))

Example output

bob@localhost:~$ echo $(( ( RANDOM % 10 ) +1 ))
10
bob@localhost:~$ echo $(( ( RANDOM % 10 ) +1 ))
2
bob@localhost:~$ echo $(( ( RANDOM % 10 ) +1 ))
9
bob@localhost:~$ 

Sleep timer

sleep $(( ( RANDOM % 10 ) +1 ))

Links on sending/receiving imessages with applescript or bash

https://apple.stackexchange.com/questions/331468/bash-script-detect-received-imessage-along-with-its-contents

Command line program to send imessage messages
https://github.com/linjunpop/imessage

Chat bot
https://github.com/ZekeSnider/Jared

Run bash commands from Applescript
https://www.cyberciti.biz/faq/mac-osx-applescript-run-shell-script/

Applescript Documentation archive
https://developer.apple.com/library/archive/documentation/AppleScript/Conceptual/AppleScriptLangGuide/introduction/ASLR_intro.html

Auto renew ssl cert for UniFI and UniFi-Video

The following script was taken from here
Added unifi-video support. Script uses letsencrypt to get the cert and automatically updates the UniFi and UniFi-Video Keystores.

Would be a good idea to check and make sure the the UniFi-Video cameras reconnect and still work.

You should be able to add the script to a cronjob to auto renew the certificate.

Run the script wit no or the -h argument to show the options and arguments to use.

./gen-unifi-cert.sh -h

Copy and paste script into gen-unifi-cert.sh file, chmod +x gen-unifi-cert.sh

#!/usr/bin/env bash
# Added support to do UniFi and UniFi controllers at the same time using the same cert.
# Original script from https://git.sosdg.org/brielle/lets-encrypt-scripts/raw/branch/master/gen-unifi-cert.sh
# More info here https://www.reddit.com/r/Ubiquiti/comments/43v23u/using_letsencrypt_with_the_unifi_controller/ 
# And here https://www.reddit.com/r/Ubiquiti/comments/43v23u/using_letsencrypt_with_the_unifi_controller/
# Modified script from here: https://github.com/FarsetLabs/letsencrypt-helper-scripts/blob/master/letsencrypt-unifi.sh
# Modified by: Brielle Bruns 
# Download URL: https://source.sosdg.org/brielle/lets-encrypt-scripts
# Version: 1.7
# Last Changed: 09/26/2018
# 02/02/2016: Fixed some errors with key export/import, removed lame docker requirements
# 02/27/2016: More verbose progress report
# 03/08/2016: Add renew option, reformat code, command line options
# 03/24/2016: More sanity checking, embedding cert
# 10/23/2017: Apparently don't need the ace.jar parts, so disable them
# 02/04/2018: LE disabled tls-sni-01, so switch to just tls-sni, as certbot 0.22 and later automatically fall back to http/80 for auth
# 05/29/2018: Integrate patch from Donald Webster  to cleanup and improve tests
# 09/26/2018: Change from TLS to HTTP authenticator

# Location of LetsEncrypt binary we use.  Leave unset if you want to let it find automatically
#LEBINARY="/usr/src/letsencrypt/certbot-auto"

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

function usage() {
  echo "Usage: $0 -d  [-e ] [-r] [-i]"
  echo "  -d : The domain name to use."
  echo "  -e : Email address to use for certificate."
  echo "  -r: Renew domain."
  echo "  -i: Insert only, use to force insertion of certificate."
}

while getopts "hird:e:" opt; do
  case $opt in
    i) onlyinsert="yes";;
    r) renew="yes";;
    d) domains+=("$OPTARG");;
    e) email="$OPTARG";;
    h) usage
       exit;;
  esac
done

DEFAULTLEBINARY="/usr/bin/certbot /usr/bin/letsencrypt /usr/sbin/certbot
  /usr/sbin/letsencrypt /usr/local/bin/certbot /usr/local/sbin/certbot
  /usr/local/bin/letsencrypt /usr/local/sbin/letsencrypt
  /usr/src/letsencrypt/certbot-auto /usr/src/letsencrypt/letsencrypt-auto
  /usr/src/certbot/certbot-auto /usr/src/certbot/letsencrypt-auto
  /usr/src/certbot-master/certbot-auto /usr/src/certbot-master/letsencrypt-auto"

if [[ ! -v LEBINARY ]]; then
  for i in ${DEFAULTLEBINARY}; do
    if [[ -x ${i} ]]; then
      LEBINARY=${i}
      echo "Found LetsEncrypt/Certbot binary at ${LEBINARY}"
      break
    fi
  done
fi

# Command line options depending on New or Renew.
NEWCERT="--renew-by-default certonly"
RENEWCERT="-n renew"

# Check for required binaries
if [[ ! -x ${LEBINARY} ]]; then
  echo "Error: LetsEncrypt binary not found in ${LEBINARY} !"
  echo "You'll need to do one of the following:"
  echo "1) Change LEBINARY variable in this script"
  echo "2) Install LE manually or via your package manager and do #1"
  echo "3) Use the included get-letsencrypt.sh script to install it"
  exit 1
fi

if [[ ! -x $( which keytool ) ]]; then
  echo "Error: Java keytool binary not found."
  exit 1
fi

if [[ ! -x $( which openssl ) ]]; then
  echo "Error: OpenSSL binary not found."
  exit 1
fi

if [[ ! -z ${email} ]]; then
  email="--email ${email}"
else
  email=""
fi

shift $((OPTIND -1))
for val in "${domains[@]}"; do
        DOMAINS="${DOMAINS} -d ${val} "
done

MAINDOMAIN=${domains[0]}

if [[ -z ${MAINDOMAIN} ]]; then
  echo "Error: At least one -d argument is required"
  usage
  exit 1
fi

if [[ ${renew} == "yes" ]]; then
  LEOPTIONS="${RENEWCERT}"
else
  LEOPTIONS="${email} ${DOMAINS} ${NEWCERT}"
fi

if [[ ${onlyinsert} != "yes" ]]; then
  echo "Firing up standalone authenticator on TCP port 80 and requesting cert..."
  ${LEBINARY} --server https://acme-v01.api.letsencrypt.org/directory \
              --agree-tos --standalone --preferred-challenges http ${LEOPTIONS}
fi

if [[ ${onlyinsert} != "yes" ]] && md5sum -c "/etc/letsencrypt/live/${MAINDOMAIN}/cert.pem.md5" &>/dev/null; then
  echo "Cert has not changed, not updating controller."
  exit 0
else
  echo "Cert has changed or -i option was used, updating controller..."
  TEMPFILE=$(mktemp)
  CATEMPFILE=$(mktemp)

  # Identrust cross-signed CA cert needed by the java keystore for import.
  # Can get original here: https://www.identrust.com/certificates/trustid/root-download-x3.html
  cat > "${CATEMPFILE}" <<'_EOF'
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
_EOF

  md5sum "/etc/letsencrypt/live/${MAINDOMAIN}/cert.pem" > "/etc/letsencrypt/live/${MAINDOMAIN}/cert.pem.md5"
  echo "Using openssl to prepare certificate..."
  cat "/etc/letsencrypt/live/${MAINDOMAIN}/chain.pem" >> "${CATEMPFILE}"
  openssl pkcs12 -export  -passout pass:aircontrolenterprise \
          -in "/etc/letsencrypt/live/${MAINDOMAIN}/cert.pem" \
          -inkey "/etc/letsencrypt/live/${MAINDOMAIN}/privkey.pem" \
          -out "${TEMPFILE}" -name unifi \
          -CAfile "${CATEMPFILE}" -caname root

  echo "Stopping Unifi and UniFi-Video controllers..."
  systemctl stop unifi unifi-video  

  echo "Removing existing certificate from Unifi protected keystore..."
  keytool -delete -alias unifi -keystore /usr/lib/unifi/data/keystore -deststorepass aircontrolenterprise
  echo "Removing existing certificate from Unifi-Video protected keystore..."
  keytool -delete -alias unifi -keystore /usr/lib/unifi-video/data/keystore -deststorepass ubiquiti
  # following lines are needed for unifi-video
 
  echo "Inserting certificate into Unifi keystore..."
  keytool -trustcacerts -importkeystore \
          -deststorepass aircontrolenterprise \
          -destkeypass aircontrolenterprise \
          -destkeystore /usr/lib/unifi/data/keystore \
          -srckeystore "${TEMPFILE}" -srcstoretype PKCS12 \
          -srcstorepass aircontrolenterprise \
          -alias unifi

  echo "Inserting certificate into Unifi-Video keystore..."
  keytool -trustcacerts -importkeystore \
          -deststorepass ubiquiti \
          -destkeypass ubiquiti \
          -destkeystore /usr/lib/unifi-video/data/keystore \
          -srckeystore "${TEMPFILE}" -srcstoretype PKCS12 \
          -srcstorepass aircontrolenterprise \

          rm -f "${TEMPFILE}" "${CATEMPFILE}"

  mv /usr/lib/unifi-video/data/ufv-truststore{,.old} # Delete old unifi-video keystore
  sleep 5
  echo "Starting Unifi and UniFi-Video controllers..."
  systemctl start unifi unifi-video 

  echo "Done!"
fi

Bash ANSI-C Quoting

Pulled from https://www.gnu.org/software/bash/manual/bashref.html#ANSI_002dC-Quoting

As a side note there is a lot of good bash info out here. https://www.gnu.org/software/bash/manual/bashref.html

3.1.2.4 ANSI-C Quoting

Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows: \a

alert (bell) \b

backspace \e\E

an escape character (not ANSI C) \f

form feed \n

newline \r

carriage return \t

horizontal tab \v

vertical tab \\

backslash \'

single quote \"

double quote \?

question mark \nnn

Some examples

echo Hello $'\t' World

Returns “Hello World” with a tab space between both words.

echo Hello $'\n' World

Returns Hello on one line and World on the second

echo "\"Hello World\""

Returns “Hello World” inside double quotes

Bash script to send messages to Microsoft Teams

Copy and save into teams.sh file. Make executable. Change web hook, Run!

The script is a modified Slack script from off the web.

#!/bin/bash
# bash script to send messages to Microsoft Teams.
function usage {
echo "HELP ME!"
echo "description: send messages to Microsoft Teams channels"
echo "special notes: You'll need to change the teamsUrl variable to contain your webhook from Teams."
echo "usage: ${0} -b \"Message contents\""
echo " -m Message body"
echo " -h This help info"
exit 1
}
while getopts "m:h" opt; do
case ${opt} in
m) msgBody="$OPTARG"
;;
h) usage
;;
\?) echo "Invalid option -$OPTARG" >&2
;;
esac
done
# Add/Change the webhook to one you created in Teams
teamsUrl="https://teamswebhook"
if [[ ! "${msgBody}" ]]; then
echo "You didn't specify a message!"
usage
fi
read -d '' payLoad << EOF
{
"text": "${msgBody}",
}
EOF
statusCode=$(curl \
--write-out %{http_code} \
--silent \
--output /dev/null \
-X POST \
-H 'Content-type: application/json' \
--data "${payLoad}" ${teamsUrl})
echo ${statusCode}