Class:01
What is Shell ?
Shell is a programm,
It will take the commands and it will gives to the OS to perform the Commands.
Shell is an interface b/w User and OS.
Types of Shells:
How to know which shell is installed in our OS?
/etc/shells
cat /etc/shells
By default Sh & Bash shells are installed in our OS.
sh
Bash
Which Shell we are using on our OS?
echo $SHELL
ps -p $$
echo $0
How to change the Shell type?
/bin/csh
/bin/ksh
/bin/sh
/bin/bash
What is the default Shell Type in latest OS?
bash
Bash Shell Scripting:
A Shell is a file containing a series of commands.
The Shell reads the file and carries out the commands as through they have been entered directly on the command line.
Normally the Shell Script has the file extension is (.sh).
Bash Shell Scripting--------Linux
PowerShell Scripting--------Windows (DOS Commands).
Why we need to learn the Shell Scripting?
- Automate the regular jobs.
- Taking database backups.
- Monotering Several Server resources like...
- CPU Utilization
- Memory Utilization
- Portable (It can be executed in any Unix-like OS without any modifications)
Server_Resource_Monitering.sh
Dbback.sh
Cleanup.sh
Deploy.sh
#!/bin/bash ---------->Shebang line
--
|
|
------->.Abslute path of shell type
How to run the Shell Script?
- ./hello.sh
- . hello.sh
- sh hello.sh
- bash hello.sh
#!/bin/bash
echo "Welcome to the world.."
echo "Today date is:"
date
How to run the Shell Script in debug mode?
sh -x hello.sh -------------------->-x ------>dubug mode
How to run the specfic debug in Shell Scripting?
set -x
echo "Welcome to the India.."
echo "Welcome to the USA.."
set +x
cat -n hello.sh
sh -x hello.sh
Class:02
Fine Naming Conventions:
Comments:
Single Line Comment: #
Multi Line Comment: <<Keyword
Keyword
Variable:
Variable is one storage location.
where we can store the values.
Types of Variables
- System Defined Variables
- How to see the System Defined variables?
- env
- printenv
- printenv | cut -d "=" -f 1,2
- echo $SHELL
- echo ${SHELL}
- User Defined Variables
Class:03
Command Line Arguments:
While executing the ShellScript, passing the values to the Shell Scripts is called Command line Arg.
echo $0 --------> Script file name
echo $1 --------> 1st arg value
echo $2 --------> 2nd arg value
echo $3 --------> 3rd arg value
echo $4 --------> 4th arg value
echo $5 --------> 5th arg value
echo $6 -------->
echo $7 -------->
echo $8 -------->
echo $9 -------->
echo ${10} ----->10th arg value
echo $* --------> Display all the arg Value --------> all arg into a one String
echo $@ -------> Display all the arg Value --------> each arg as a one string
echo $# --------> No.of Arguments.
echo $$ --------> Process ID.
echo $? --------> Previous command execution status.
0 = Sucellfull
apart from 0 = failure
#!/bin/bash
echo "Commnad Line Argument demo..."
if [ $# -eq 2 ];
then
echo $0
echo $1
echo $2
echo $$
echo $?
echo $#
else
echo "Please pass minume 2 Arguments."
echo "Usage: sh $0 arg1 arg2 "
fi
String:
String is a group of charactors enclosed in a singe or double quotes.
string_value="Hi Team My Name is ReddySekhar, I am working in IBM in Mumbai Location..."
Sub-String:
Some poration of value in the original String.
substring =
echo ${string_value:20} ---> ReddySekhar, I am working in IBM in Mumbai Location...
echo ${string_value:20:11} ----------> ReddySekhar
echo ${string_value: -10} ------------> Location..
echo ${string_value: (-10)} ------------> Location..
Arithmetic Operations:
- expr 2 + 3
- expr 2 - 3
- expr 2 * 3 -------------------expr 2 \ * 3
- expr 10 / 2
- expr 30 % 3
Write a ShellScript, accept the 2 numbers from the user, and perform the arthmetic Operations?
Class:04
Read Command:
echo "Please enter your name"
read UserName
echo "The User name is:"$UserName
What is an Array?
Inputs and Outputs Redirections Symbols:
> ------> Redirect Standard O/P
>> ------> Appending the Standard O/P
< ------> Redirect Standard I/P
How to store Std I/P & Std O/P?
sh filename.sh 1 2 > filename.log ------------>it's redirect Std O/P only
sh filename.sh 1 2 > filename.log 2>&1
File Descriptors:
Class:05
Class:06
Labels: Mithun Technologies
