How do you write a while loop in Unix?

How do you write a while loop in shell script?

Shell Script While Loop Examples

1. while [ condition ] do command1 command2 commandN done.
2. while [[ condition ]] ; do command1 command1 commandN done.
3. while ( condition ) commands end.
4. #!/bin/bash c=1 while [ $c -le 5 ] do echo “Welcone $c times” (( c++ )) done.

How do you use a while loop in bash?

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.

What is the function of while loop?

The while loop is used to repeat a section of code an unknown number of times until a specific condition is met. For example, say we want to know how many times a given number can be divided by 2 before it is less than or equal to 1.

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 do a while loop in terminal?

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 an infinite loop in shell script?

To set an infinite while loop use:

1. true command – do nothing, successfully (always returns exit code 0)
2. false command – do nothing, unsuccessfully (always returns exit code 1)
3. : command – no effect; the command does nothing (always returns exit code 0)

How do I run a shell script?

Steps to write and execute a script

1. Open the terminal. Go to the directory where you want to create your script.
2. Create a file with . sh extension.
3. Write the script in the file using an editor.
4. Make the script executable with command chmod +x <fileName>.
5. Run the script using ./<fileName>.

What means while loop?

Overview. A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The while loop can be thought of as a repeating if statement.