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what is a shell?
Shell is a program. It will take the commands that the user is typing and it will give them to the OS to execute
shell is an interpreter user and the OS
The default shell is bash in advance Linux system
What are the shell types?
Sh, bash, ksh, zsh, csh. In etc/shells we can see shells
-->To view it we use cat etc/shells
cat etc/shells _ to know what the shells are available in that particular Linux server
/bin/shell name_ to switch to that particular shellecho SHELL- whatever you give with the echo cmd display as it is like "SHELL"-here shell is a variable
if you want that variable value then give "
$" before the variable
what is the shell scripting?
- It is a file. It contains a list or series of commands. The shell reads the file and carries out the commands as though they have been entered directly into the command line.
- all the shell scripts file extension is ' .sh '
why we need shell scripts?
to automate the regular backups
taking database backups
monitor the several server resources like CPU utilization and memory utilization
portable (it can be executed in any UNIX-like operating system without modifications)
prerequisites
Linux/Unix/AIX server
knowledge of Linux commands with various options
basic programming knowledge
The first shell scripting program on ECHO(hello.sh)
eix --> shebang line #!
To execute the shell file we have to ./hello.sh. hello.sh sh hello.sh, bash hello. sh
First see where the shell scripts are there
- Don’t forget to change the mode of files and folder before doing it
How to run the shell script in debug mode sh -x sample.sh
in a script, we have to put it -x example
