Understanding Shell Scripting with Basic

Last Blog Review →

In the last blog we understood,the logic of writing the cronjob commands.

A. What is script ?

\=> Script in which there are sequence of commands for a UNIX-based operating system. Also, they are written in Shell which is a black screen you see. Extension of shell script file is ".sh". The type of shell which we are using is bash. To know which type of shell we are using "echo $shell".

B. What is “#!“ ?

\=> While writing any shell scripting we need to start with "#!" which is called as sharp-exclamation, sha-bang, hashbang, pound-bang, or hash-pling. Then we need to check which type of shell we are having in the Linux OS. using command "echo $SHELL". In this Linux OS we have GNU based Bourne-Again Shell denoted by "bash". So, along with "#!" we will write the type of shell we have i.e bash & bash is in bin directory so "#!/bin/bash"

C. “echo” to print the output ?

\=> In shell scripting to print anything we use "echo" command, for ex. echo "hi"

D. What is variable ?

\=> Variables are who vary. Variables and Constants are differentiated as "Variables start with $ sign". While assigning a value to a variable $ sign is not req. Only when variables are used then use $ sign. Variables in Shell scripting are case sensitive and are alphanumeric and underscores i.e. only alphabets, numbers, underscores are allowed.

Now if we want to use inbuilt variable to be written in "echo" statement then we can write in this format $(inbuilt_variable_name).

for ex. date is a inbuilt command and we want to use it in echo command to display date, then write : echo "Today is $(date)"

If we want to use an user-defined variable to be written in "echo" statement, then we write in this format $user-defined-variable-name.

for ex. this is a user-defined-variable and it has my name, name = Mihir and we want to print it then write : echo "$name".

E. Commenting in shell script ?

\=> To give single line comment in shell script use "#"

Conclusion →

In this blog we understood, the simple shell scripting basic’s which are highly necessary when we start writing the shell scripts. Understanding what is script, what is #!, how to declare variables, how to add comments.

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