Run the above script with employee. The output will show the content of employee. You can show the original content of employee. Create a file named company2. The output will show the file content without any backslash. You will need to read the file for many programming purposes. For example, you can search or match any particular content easily from any file by reading each line separately.
So, it is an essential task for any programming. Some simple examples of reading file in bash script are shown in this tutorial. If you want to continue down the bash shell road, you can do something like this:.
If a line begins with 'Item', save the item name in ITM. Splitting on : makes it easier to get the item name. The assumption is that groups of subitems will always be preceded by an Item: entry, so the variable ITM should always have the name of the current group. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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Viewed 19k times. Improve this question. FanaticD FanaticD 1, 3 3 gold badges 19 19 silver badges 34 34 bronze badges. No, you don't need two loops. Is this an assignment? We had someone else with the same problem, also coming in with the misconception that nested loops were the right solution not so long back. By submitting your email, you agree to the Terms of Use and Privacy Policy.
Each programming language has a set of idioms. These are the standard, no-frills ways to accomplish a set of common tasks. Actions like reading data from files, working with loops, and swapping the values of two variables are good examples. The programmer will know at least one way to achieve their ends in a generic or vanilla fashion. Perhaps that will suffice for the requirement at hand. But having the building-block idiom at their fingertips is a great starting point. Knowing and understanding idioms in one language makes it easier to pick up a new programming language, too.
In Bash, you can use a while loop on the command line to read each line of text from a file and do something with it. The while loop reads a line from the file, and the execution flow of the little program passes to the body of the loop. The echo command writes the line of text in the terminal window. The read attempt fails when there are no more lines to be read, and the loop is done.
One neat trick is the ability to redirect a file into a loop. With Bash, you can simply use file redirection and let the shell handle all of that low-level stuff for you. Linux already provides the cat command, which does exactly that for us. But it does visibly demonstrate the principles of reading from a file. That works well enough, up to a point.
Suppose we have another text file that contains the names of the months. In this file, the escape sequence for a newline character has been appended to each line. Bash is interpreting the backslash as the start of an escape sequence. It can be more convenient to read a line in its entirety—backslash escape sequences and all—and choose what to parse out or replace yourself, within your own code. We set a variable called Counter to zero, then we define our while loop.
IFS stands for internal field separator. It holds values that Bash uses to identify word boundaries. By default, the read command strips off leading and trailing whitespace.
If we want to read the lines from the file exactly as they are, we need to set IFS to be an empty string. But with more complex scripts—especially those with many user-defined functions in them—it is possible that IFS could be set to different values elsewhere in the script. Ensuring that IFS is set to an empty string each time the while loop iterates guarantees that we know what its behavior will be.
There are two conditions that will satisfy the while loop and allow the text to be processed by the body of the loop:. The line number and the text of each line are displayed. We can still use our redirection trick to redirect a file into a loop.
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