store file content in shell variable

How to Store File Content in Shell Variable

Typically, Linux administrators and developers use shell variables to store strings and numbers. But sometimes you may need to store file content in shell variable. In this article, we will learn how to do this.


How to Store File Content in Shell Variable

Let us say you have the following text file data.txt.

text1
text2

We use cat function to output the file contents.

cat data.txt

We assign the output of above command to a shell variable test_var using the following command.

test_var = $(cat test.txt)

Generally, administrators use the following command to output the contents of a variable.

echo $variable

If we do this with the above variable, you will see the following output.

# echo $test_var
text1 text2

You will see that the newline has been omitted in the above output.

To display the file contents exactly as they are, you need to enclose the shell variable within quotes, as shown below.

# echo "$test_var"
text1
text2

Now the file contents are displayed exactly as they are. This happens because when you issue a command in Linux shell, it uses IFS (internal field separator) to split the output after expansion using space/tab/newline, and any of these can be used to split the output into a list of words. So the shell reformats the output such that all words are separated by space and a newline is added only at the end of the output.

When we use quotes around our shell variable, it forces bash to treat the entire output of variable (that is, file content) within quotes, as a single string, and it is not split.

In this article, we have learnt how to store file content in shell variable.

Also read:

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How to Get Multiline Strings in JavaScript
How to Split String by Particular Character

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