- Nikhil Bhaskar
- July 8, 2021
Shell Scripting is an open-source system program designed to be run by the Unix/Linux shell.It is a program to write a lines of commands for the shell to execute.
A shell script or sh-file is between a single command and a small program.We have multiples shell command & running multiple commands together.It is used for perform multiple tasks automatically.
Create a Shell Script.
Write a simple code.
#!/bin/bash # Print Example message echo "Example!"
Provide execute permission.
chmod +x scriptfile.sh
Run the script file.
bash scritpfile.sh or ./scriptfile.sh
Here is the command output.
root@ip-172-15-25-65:/home/ubuntu#bash scriptfile.sh Example!
Syntax of Script file program
Only if Statement
- It is used to test single or multiple conditions.
if command then statement fi
- It is used when we have 2 possible outcomes.
if command then statement1 else statement2 fi
- It is used when we have multiple conditions and different outcomes.
if condition1 then statement1 elif condition2 then statement2 else statement3 fi
- It is used to print the lines.
#!/bin/bash echo "Print the message"
It is a control flow statement that executes a block of code at least once, and then repeatedly executes the code or not, depending on a given boolean condition at the end of the block.
#!/bin/bash valid=true count=1 while [ $valid ] do echo $count if [ $count -eq 5 ]; then break fi ((count++)) done
It is a repetition control program that allows to efficiently write a loop that needs to execute a specific number of times.
#!/bin/bash for (( counter=10; counter>0; counter-- )) do echo -n "$counter " done printf "\n"
- It is is used to take input from user in bash.
echo "Enter Name" read name echo "$name"
- We can add,substract,multiply & divide the number is bash program.
Add Two numbers.
#!/bin/bash echo "Enter first number" read x echo "Enter second number" read y (( sum=x+y )) echo "The result of addition=$sum"
- We can create a folder/directory using bash file.
#!/bin/bash echo "Enter directory name" read newdir `mkdir $newdir`
- We can read any file line by line in bash by using loop.
#!/bin/bash file='book.txt' while read line; do echo $line done < $file
#!/bin/bash echo "Enter file-name to delete" read fn rm -i $fn
- Using bash, we can send a mail.
#!/bin/bash Recipient=”[email protected]” Subject=”Topic” Message=”Welcome” `mail -s $Subject $Recipient <<< $Message`