How to Create a Shell and Subshell on Oracle Linux 9.2

To Create A Shell And Subshell On Oracle Linux 9.2

Introduction

What is Shell?

A shell is a special program that acts as an interpreter between the user and the operating system. Shell accepts human-readable commands from a user and converts them into Kernel-readable language. It is a command language interpreter that executes commands read from input devices such as keyboards or from files. The shell gets started when the user logs in or starts the terminal.

What is Subshell?

Subshell is an important concept in shell scripting that allows you to execute commands within a separate shell environment. They can be created using the parentheses operator or the bash command, and they provide a way to isolate the effects of specific commands or operations.

Creation Steps:

Step 1: First Check the OS version by using the Following commands

[root@linuxhelp ~]# cat /etc/os-release
NAME="Oracle Linux Server"
VERSION="9.2"
ID="ol"
ID_LIKE="fedora"
VARIANT="Server"
VARIANT_ID="server"
VERSION_ID="9.2"
PLATFORM_ID="platform:el9"
PRETTY_NAME="Oracle Linux Server 9.2"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:oracle:linux:9:2:server"
HOME_URL="https://linux.oracle.com/"
BUG_REPORT_URL="https://github.com/oracle/oracle-linux"
ORACLE_BUGZILLA_PRODUCT="Oracle Linux 9"
ORACLE_BUGZILLA_PRODUCT_VERSION=9.2
ORACLE_SUPPORT_PRODUCT="Oracle Linux"
ORACLE_SUPPORT_PRODUCT_VERSION=9.2

Step 2: Next create a one script file by using Vim command

[root@linuxhelp ~]# vim script1
#!/bin/bash   It is the first line should be present in every shell scripts. It’s called a shebang.
var=root
echo $var
echo $name

Step 3 : Using export command to assign the value for name variable.It is used to mark variables and functions to be passed to child processes.

[root@linuxhelp ~]# export name=linux

Step 4 : To execute the script first change the executable file permission by using the following command

[root@linuxhelp ~]# chmod +x script1

Step 5: To list the file by using the following commands

[root@linuxhelp ~]# ll
total 8
-rw-------. 1 root root 1062 Sep  4 17:37 anaconda-ks.cfg
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Desktop
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Documents
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Downloads
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Music
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Pictures
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Public
-rwxr-xr-x. 1 root root   45 Sep  6 20:23 script1
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Templates
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Videos

Step 6 : To execute the script by using the following command

[root@linuxhelp ~]# ./script1
root
linux

Step 7 :Next Copy the script1 file to script2 file by using the following command.

[root@linuxhelp ~]# cat script1 >> script2

Step 8: To list the file by using the following commands

[root@linuxhelp ~]# ll
total 12
-rw-------. 1 root root 1062 Sep  4 17:37 anaconda-ks.cfg
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Desktop
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Documents
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Downloads
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Music
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Pictures
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Public
-rwxr-xr-x. 1 root root   45 Sep  6 20:23 script1
-rw-r--r--. 1 root root   45 Sep  6 20:45 script2
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Templates
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Videos

Step 9 : Add some command in script 2 file by using Vim command

[root@linuxhelp ~]# vim script2
#!/bin/bash
var=root
echo $var
echo $name
pwd
ls

Step 10 : To execute the script first change the executable file permission by using the following command

[root@linuxhelp ~]# chmod +x script2

Step 11: To list the file by using the following commands

[root@linuxhelp ~]# ll
total 12
-rw-------. 1 root root 1062 Sep  4 17:37 anaconda-ks.cfg
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Desktop
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Documents
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Downloads
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Music
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Pictures
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Public
-rwxr-xr-x. 1 root root   45 Sep  6 20:23 script1
-rwxr-xr-x. 1 root root   61 Sep  6 20:46 script2
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Templates
drwxr-xr-x. 2 root root    6 Sep  6 20:10 Videos

Step 12: To execute the script by using the following command

[root@linuxhelp ~]# ./script2
root
linux
/root
anaconda-ks.cfg  Desktop  Documents  Downloads  Music  Pictures  Public  script1  script2  Templates  Videos

Conclusion:

We have reached the end of this article. In this guide, we have walked you through the steps required to create user by using Shell Script on Oracle Linux 9.2. Your feedback is much welcome.