Save time 3. The working of while loop in BASH Scripting is similar to that in C Language. If you are new to Shell Scripting, I recommend that, you should read my article -. Fileinfo: operating on a file list contained in a variable. Syntax of Bash While Loop To replace while loop condition while [ $n -le 5 ] with while (( num <= 10 )) to improve code readability: You can read a text file using read command and while loop as follows (whilereadfile.sh): You can store above output in two separate fields as follows (whilereadfields.sh): Another useful example for reading and phrasing /etc/passwd file using the while loop (readpasswd.sh): From Linux Shell Scripting Tutorial - A Beginner's handbook, Using ((expression)) Format With The While Loop, # set field separator to a single white space, https://bash.cyberciti.biz/wiki/index.php?title=While_loop&oldid=3532, Attribution-Noncommercial-Share Alike 3.0 Unported, About Linux Shell Scripting Tutorial - A Beginner's handbook. We will count from 10 to 20 and print out the results. Use a While...End While structure when you want to repeat a set of statements an indefinite number of times, as long as a condition remains True. While Loops. Live Demo. Bash Scripting Tutorial - 6.Loops While Loops. The block of commands keeps executing till the condition is valid. There is a block of commands and there is a condition. echo "Running $n time". #. cat asdf | while read a ; do mv $a $a.new ; done. Bash While Loop is a loop statement used to execute a block of statements repeatedly based on the boolean result of an expression, for as long as the expression evaluates to TRUE. And [ $i -lt 4 ] is the condition: your loop will be running until $i is less than 4. do –» This tells to the command line that here starts the command that you want to execute repeatedly. So we can use a loop and iterate from 1 to 10 and print the current item. If the condition... Read a … Upon execution, you will receive the following result −. Once the condition is un-matched, it exists. Example-1: Iterate the loop for fixed number of times. (adsbygoogle = window.adsbygoogle || []).push({}); ← Nested for loop statement • Home • : infinite while loop →. Have a look on 'while' loop syntax: Basic Linux Shell Scripting Language : 'While' Loops, Basic Linux Shell Scripting Language : Introduction to 'For' Loops, Getting Started - Linux Shell Scripting Language, Getting Started - Basic Linux Shell Scripting Language, Basic Linux Shell Scripting Language - Creating Shell Scripts, Basic Linux Shell Scripting Language - Arithmetic Operations, Basic Linux Shell Scripting Language : Introduction to 'FOR' Loops, Sed Command in Linux - Append and Insert Lines to a File, How to Install or Upgrade Python in Linux Systems, /etc/passwd File Format in Linux Explained, Sed Command in Linux - Delete Lines from a File. While loop depend on the condition is true, if the condition is false the interpreter get out from the loop. For and Read-While Loops in Bash How to loop, aka designing a program to do repetitive work for you The loop is one of the most fundamental and powerful constructs in computing, because it allows us to repeat a set of commands, as many times as we want, upon a list of items of our choosing. Please note that depending on what you are doing with the loop, you may need to add a sleep command otherwise it will be annoying/difficult to terminate. The working of while loop in BASH Scripting is similar to that in C Language. Using Bash For Loop to Create an Infinity Loop. Command line while loop.. For loops with the find command. Eliminate repetitive tasks 2. Create a file with the contents you want to rename (ls -l | awk ‘{print $9}’ > asdf or something) Contents of asdf: file1 file2 file3 file4. (( n++ )) done. When condition becomes false, the 'while' loop terminates. #!/bin/sh a=0 while [ $a -lt 10 ] do echo $a a=`expr $a + 1` done. 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