Working with WHILE Loop in Bash Shell Scripting

The bash while loop is a control flow statement that allows code or commands to be executed repeatedly based on a given condition. For example, run echo command 5 times or read text file line by line or evaluate the options passed on the command line for a script.

1. How do you use a while loop in bash?
2. How do you run a while loop in shell script?
3. What does && mean in bash?
4. How do you write a while loop in batch file?
5. How do you break out of a while loop in bash?
6. How do I read a while loop in Linux?
7. How do you write a while loop in Linux?
8. How do you end a while loop?
9. Which keywords are used in while loop?
10. How do you use && in bash?
11. What is the difference between && and & operator?
12. How does bash script work?

How do you use a while loop in bash?

The while loop is used to performs a given set of commands an unknown number of times as long as the given condition evaluates to true. The while statement starts with the while keyword, followed by the conditional expression. The condition is evaluated before executing the commands.

How do you run a while loop in shell script?

Syntax. Here the Shell command is evaluated. If the resulting value is true, given statement(s) are executed. If command is false then no statement will be executed and the program will jump to the next line after the done statement.

What does && mean in bash?

Logical AND operator(&&):

The second command will only execute if the first command has executed successfully i.e, its exit status is zero. This operator can be used to check if the first command has been successfully executed.

How do you write a while loop in batch file?

There is no direct while statement available in Batch Script but we can do an implementation of this loop very easily by using the if statement and labels.

How do you break out of a while loop in bash?

You can use the break command to exit from any loop, like the while and the until loops. The loop runs until it reaches 14 then the command exits the loop. The command exits the while loop, and that happens when the execution reaches the if statement.

How do I read a while loop in Linux?

The following syntax is used for bash shell to read a file using while loop:

1. while read -r line; do. echo "$line" ; done < input.file.
2. while IFS= read -r line; do. echo $line; done < input.file.
3. $ while read line; do. echo $line; done < OS.txt.
4. #!/bin/bash. filename='OS.txt' n=1. ...
5. #!/bin/bash. filename=$1. while read line; do.

How do you write a while loop in Linux?

Syntax of while loop:

1. n=1. while [ $n -le 5 ] do. echo "Running $n time" (( n++ )) done.
2. n=1. while [ $n -le 10 ] do. if [ $n == 6 ] then. echo "terminated" break. fi. echo "Position: $n" (( n++ )) done.
3. n=0. while [ $n -le 5 ] do. (( n++ )) if [ $n == 3 ] then. continue. fi. echo "Position: $n" done.

How do you end a while loop?

The break statement exits a for or while loop completely. To skip the rest of the instructions in the loop and begin the next iteration, use a continue statement. break is not defined outside a for or while loop. To exit a function, use return .

Which keywords are used in while loop?

While Statement. This statement repeats a series of statements while a specified condition is true. endwhile; The while statement, also called the while loop, executes the series of statements between the do and endwhile keywords as long as the specified condition remains true.

How do you use && in bash?

&& Can also be used inside of the built-in test command in bash [[ ]] to combine expressions in a similar fashion as combining commands. The entire test operation will only be true if both operands (sides) of && are true, for example: if [[ ( $a -gt 2 ) && ( $a -lt 5 ) ]]; then ...

What is the difference between && and & operator?

& is a bitwise operator and compares each operand bitwise. It is a binary AND Operator and copies a bit to the result if it exists in both operands. ... Whereas && is a logical AND operator and operates on boolean operands. If both the operands are true, then the condition becomes true otherwise it is false.

How does bash script work?

A Bash script is a plain text file which contains a series of commands. These commands are a mixture of commands we would normally type ouselves on the command line (such as ls or cp for example) and commands we could type on the command line but generally wouldn't (you'll discover these over the next few pages).