Let's break the script down. It seems that I am only able to use local variables within a while loop that is reading a file. Let's break the script down. For longer files, I'll work on my computer's text editor (Sublime Text) and then upload to the server. In a BASH for loop, all the statements between do and done are performed once for every item in the list. Example 3 - How to write a UNIX shell script with a while loop that reads each line in a text file Shell scripts will frequently need to read the contents of a file, line by line, and store each line in a shell variable for additional processing. Let us see in this article how to read and parse a file field by field or column by column and extract data from it using the while loop of shell. ) and also incremented the value of (i) inside the loop and at the end I am getting the wrong value of i, the main reason is that the usage of pipe (|) will create a new sub-shell to read the file and any operation you do within this while loop (example – i++) will get lost when this sub-shell … The read command is useful for assigning variables at the time of executing a script, a kind of interactive script. Solution: A simple way to process every line in a text file is to use a Unix/Linux while loop in combination with the Linux cat command , like this: The concepts of loop are to implement these repetitive task through code and create powerful constructs through codes without any human intervention. For loop check if a directory is empty or not in shell script; loop through files in a directory in shell script; replace last n characters of a string in shell script; check if a file is empty in shell script; keyboard shortcuts for moving cursor on command line; Read from file in shell script; create symbolic link in linux; shell date examples; More – fedorqui 'SO stop harming' Aug 30 '16 at 9:44 Here we will see what kind of loops can be used for reading a file. What is Shell Script Read File? Oh, I see many things have happened here: all the comments were deleted and the question being reopened. Using a while loop coupled with a read statement is a perfect way to accomplish this task. The file contains 3 fields: OS, the company and a random value. I am writing a shell script using the korn shell. On many Unix (but not GNU/Linux) systems, this can also be done as: while3b.sh #!/bin/sh while f=`line` do .. process f .. done < myfile But since the while read f works with any *nix, and doesn't depend on the external program line , the former is preferable. When running a script: We can assign values to variables when we are in middle of the script. Just for reference, the accepted answer in Read a file line by line assigning the value to a variable addresses the problem in a canonical way and should be preferred over the accepted one here. Use nano to work on loops and save them as shell scripts. It's been a while since I wrote shell scripts. This article will also explain the usage of shell while loop. Here is a sample cat file.txt... (4 Replies) Exercise with web scraping. Learn read command with examples The read command syntax Let us consider a file with sample contents as shown below. Just to ground the syntax and workings of the for-loop, here's the thought process from turning a routine task into a loop: The following shell script will prompt the user to enter a file name and then it will read the file content line by line using the while loop and will assign each line into a variable and then it will print on the screen. Overview of Unix Shell Loops and Different Loop Types like: Unix Do While Loop; Unix For Loop; Unix Until Loop; In this tutorial, we will cover the control instructions that are used to iterate a set of commands over a series of data. All these solve different purposes on when to assign values to variables. (I can't access a variable outside a previously used while loop.) 1. Read a File Line by Line Using Shell Script. There are eventually 2 loops through which it is possible to read a file. The Bash way of using for loops is somewhat different from the way other programming and scripting languages handle for loops. 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