13. tr (Translate)

The tr command, short for translate, is a command-line utility in Linux that translates or deletes characters from standard input. It is a useful tool for simple text manipulation and is often used with pipes to process the output of other commands. The trtranslate functionality is a core part of text processing.

Basic Character Translation

The most common use of tr is to substitute one set of characters for another. For example, you can easily translate all lowercase characters to uppercase.

$ echo "hello world" | tr a-z A-Z
HELLO WORLD

In this example, we piped the output of echo to the tr command. The tr command then translated the character range a-z into the corresponding characters in the range A-Z.

Deleting Characters with -d

Another powerful feature is the ability to delete specific characters using the -d (delete) option. This is particularly useful for cleaning up text. For instance, if you want to remove all digits from a string, you can use linux tr -d.

$ echo "My address is 123 Main Street" | tr -d '0-9'
My address is  Main Street

Here, the tr -d command deleted every character in the specified set ('0' through '9') from the input stream. This is a common pattern for tr -d linux users.

Squeezing Repeated Characters

The tr command can also "squeeze" repeated characters into a single instance using the -s (squeeze) option. This is great for normalizing text with extra whitespace.

$ echo "Hello      World,   how   are   you?" | tr -s ' '
Hello World, how are you?

In this case, tr -s ' ' replaced sequences of multiple spaces with a single space, making the output much cleaner.