What are the different options available in the tr command?

The tr Command in Linux

The tr command in Linux is a powerful tool used for character translation or deletion. It is a versatile command that can perform a wide range of operations on text data. In this answer, we will explore the different options available in the tr command and provide examples to help you understand its usage.

Basic Syntax

The basic syntax of the tr command is as follows:

tr [OPTION] SET1 [SET2]

Here, SET1 and SET2 are the sets of characters that you want to translate or delete.

Available Options

The tr command offers several options to customize its behavior. Let's explore the most common ones:

1. Character Translation:

   • -c, --complement: Complement the set of characters in SET1.
   • -d, --delete: Delete characters in SET1 from the input.
   • -s, --squeeze-repeats: Replace consecutive occurrences of the same character in SET1 with a single occurrence.
   • -t, --truncate-set1: Truncate SET1 to the length of SET2.

2. Character Classification:

   • [:alnum:]: Alphanumeric characters.
   • [:alpha:]: Alphabetic characters.
   • [:digit:]: Numeric characters.
   • [:lower:]: Lowercase alphabetic characters.
   • [:upper:]: Uppercase alphabetic characters.
   • [:space:]: Whitespace characters (spaces, tabs, newlines, etc.).
   • [:punct:]: Punctuation characters.

3. Escape Sequences:

   • \a: Alert (bell).
   • \b: Backspace.
   • \f: Form feed.
   • \n: Newline.
   • \r: Carriage return.
   • \t: Horizontal tab.
   • \v: Vertical tab.

4. Range Specification:

   • You can specify a range of characters using the - symbol, e.g., a-z or A-Z.

Examples

1. Translating Uppercase to Lowercase:

   echo "HELLO, WORLD!" | tr "A-Z" "a-z"

   Output: hello, world!

2. Deleting Specific Characters:

   echo "Hello, World!" | tr -d "," "!"

   Output: Hello World

3. Squeezing Repeated Characters:

   echo "Hello   World!" | tr -s " "

   Output: Hello World!

4. Complementing a Set of Characters:

   echo "Hello, World!" | tr -c "a-zA-Z" "_"

   Output: _e_l_l_o__W_o_r_l_!_

5. Translating Characters Based on Character Classification:

   echo "Hello123, World456!" | tr "[:digit:]" "X"

   Output: HelloXXX, WorldXXX!

By understanding the different options available in the tr command, you can perform a wide range of text manipulation tasks, such as character translation, deletion, and transformation. The examples provided should give you a good starting point to explore the capabilities of this powerful Linux tool.