Understanding the tr Command

Introduction to the tr Command

The tr command in Linux is a powerful tool used for translating or deleting characters. It stands for “translate” or “transliterate.” With tr, you can perform various text transformation tasks, such as replacing characters, converting lowercase to uppercase (and vice versa), deleting specific characters, and more.

Basic Syntax

The basic syntax of the tr command is as follows:

tr [options] SET1 [SET2]

• SET1: Specifies the set of characters to be replaced or deleted.
• SET2: Specifies the set of characters to replace SET1 with.

Common Options

Here are some common options used with the tr command:

• -d: Deletes characters in SET1.
• -s: Squeezes repeated occurrences of characters in SET1 to a single occurrence.
• -c: Complements SET1; replaces characters not in SET1.
• -t: Truncate SET1 to the length of SET2 if SET2 is shorter.

Examples

Example 1: Translating Characters

To convert all lowercase characters in a file to uppercase, you can use the following command:

tr [:lower:] [:upper:] < input.txt > output.txt

Example 2: Deleting Characters

To remove all digits from a text file, you can use the following command:

tr -d 0-9 < input.txt > output.txt

Example 3: Squeezing Repeated Characters

To squeeze repeated occurrences of whitespace characters into a single space, you can use the following command:

tr -s ' ' < input.txt > output.txt

Conclusion

The tr command is a versatile tool for manipulating text in Linux. By mastering its usage and understanding its options, you can perform a wide range of text transformation tasks efficiently. Whether you need to translate characters, delete specific characters, or squeeze repeated occurrences, the tr command has got you covered.

📝 For more information about the tr command, you can refer to the tr man page.