shell scrpting

---------------

command line argument

$1 $2 ...$9 , $11

read # read through we can pass the argument

#Create user & group

#!/bin/bash

user_group="avinna" # user_group=$2

if [ "$user_group" == "avinna" ]

then

echo "user group $user_group exists !!"

else if [ "$user_group" == "devops" ]

then

echo "Admin of server"

else

echo "invalid group"

fi

----------------------------

#check dir & if not create the dir

#! bin/bash

config_dir=$1

if [ -d "config" }

then

config_files=$(ls config)

echo "reading config dir contents: $config_files"

else

echo "config dir doesn't exists, createing one..."

mkdir config_dir

touch "$config_dir/data.txt"

touch "$config_dir/data2.txt"

fi

------------------------------------

# read throug create user & paaswd

#!/bin/bash

read -p "please enter your name" name

echo "welcome to devops $name "

--------------------------------

#! /bin/bash

echo -n "welcome to devops youtube channel"

read -p "enter your username: " user

read -p "enter your password: " passwd

if [ "$passwd" == "avinna123" ]

then

echo 'Login successsful !!!"

else

echo " login failed !!"

fi

--------------------------------------

$1 - first argument

$2 - second argument

$3 - third argument

$* - all parameters arguments shows

$# - number of arguments

$? - last command result

Loops

while

for

until

select

for loop [ - - - ]

vi for.sh

#!/bin/bash

for param in $#

do

echo "parameter: $param"

done

------------------------

#! /bin/bash

echo "num of params $#"

for param in $* # for i in [ condition ]

do

if [ -d "$param" ]

then

echo "executing script into dir"

ls -l $param

fi

echo "parameter: $param"

done

----------------------------

while loop while cond

---------

while condition

do

done

#!/bin/bash

sum=0

while true

do

read -p "enter a number: " num

if [ "sum" = "q" ]

then

break

fi

sum=$((sum + num))

echo "Sum of numbers: $num"

done

-------------------------------

function sum(){

sum=0

while true

do

read -p "enter a number: " num

if [ "sum" = "q" ]

then

break

fi

sum=$((sum + num))

echo "Sum of numbers: $num"

done

}

sum

------------------------------------

#!/bin/bash

function create_file(){

file_name=$1

touch $file_name

echo "file : $file_name is created"

}

create_file test.sh

create_file abc.yaml

create_file data4.txt

----------------------------

# vi /opt/scripts/os-log-alert.sh

#!/bin/bash

#Set the variable which equal to zero

prev_count=0

count=$(grep -i "`date --date='yesterday' '+%b %e'`" /var/log/messages | egrep -wi 'warning|error|critical' | wc -l)

if [ "$prev_count" -lt "$count" ] ; then

# Send a mail to given email id when errors found in log

SUBJECT="WARNING: Errors found in log on "`date --date='yesterday' '+%b %e'`""

# This is a temp file, which is created to store the email message.

MESSAGE="/tmp/logs.txt"

TO="[email protected]"

echo "ATTENTION: Errors are found in /var/log/messages. Please Check with Linux admin." >> $MESSAGE

echo "Hostname: `hostname`" >> $MESSAGE

echo -e "\n" >> $MESSAGE

echo "+------------------------------------------------------------------------------------+" >> $MESSAGE

echo "Error messages in the log file as below" >> $MESSAGE

echo "+------------------------------------------------------------------------------------+" >> $MESSAGE

grep -i "`date --date='yesterday' '+%b %e'`" /var/log/messages | awk '{ $3=""; print}' | egrep -wi 'warning|error|critical' >> $MESSAGE

mail -s "$SUBJECT" "$TO" < $MESSAGE

#rm $MESSAGE

fi