Wildcards in Linux: Understanding and Using Placeholders

Working with files in Linux can be time-consuming, especially when it comes to interacting with large amounts of data. This is where wildcards or placeholders come into play, helping you navigate and find files more efficiently and quickly. This guide shows you the different types of wildcards in Linux and explains how you can use them in the terminal.

Key Takeaways

• Wildcards are special symbols that stand for other characters and help refine search queries.
• The most common wildcard characters are the asterisk (*), the question mark (?), and square brackets ([]).
• You can combine wildcards to achieve more precise or broader search results.

Using Wildcards in Linux

Wildcards and Their Meanings

Wildcards are symbols used in the command line to select groups of files or specific files based on their names. A typical example in the terminal is the asterisk (*), which stands for zero or more characters.

Display All Files Starting with a Specific Letter

Assuming you want to list all files that start with the letter "S". You can do this with the following command:

ls S*

This command will show you all files that start with the letter "S", followed by any characters.

Filter Files with Specific Extensions

If you want to list all files that end with "A2", you can do it like this:

ls *A2

This command will show you all files that end with "A2", regardless of whether they have an extension like.txt or.pdf.

Specify Strings with Placeholders

Sometimes you need a more specific search query. Suppose you want only the files that start with "SO". The command for that is:

ls SO*

Here, "SO" is combined with any further characters to return a filtered list of files.

Using the Question Mark for Wildcard Searches

The question mark (?) stands for exactly one character. If you are looking for a file like "TO", you can also enter:

ls T?

This command will find "TO" as well as "TA", "TB", etc., because the question mark stands for any single character.

Ambiguous Strings

If you are looking for a file whose name consists of three characters, with two of them unknown, you can use the question mark for the unknown characters:

ls???A3

This will find files like "P1A3", "P2A3", and so on.

Using Square Brackets

With square brackets, you can specify ranges or specific characters. For example, to show only the files that contain "E", "N", or "O" in the middle, you can use the following command:

ls S[EN]*

This searches explicitly for files that start with "S" and have either "E" or "N" as the second letter.

Combining Wildcards

The combination of different wildcards can help you search even more precisely. For example, to display all files that contain a number between 1 and 3, the command looks like this:

ls *[1-3]*

Here, the asterisk is used as a placeholder for any characters, while the brackets specify the number between 1 and 3.

Filter Specific Characters at the Beginning or End

If you want the listing of files to show only those that start with a number between 0 and 9, you can implement it like this:

ls [0-9]*

This will show you all files that start with a number.

Summary – How Wildcards Work in Linux

Understanding and implementing wildcards in Linux is essential for efficiently navigating a file structure. Whether you are looking for specific files or wishing to filter groups, placeholders allow you to work effectively with the terminal. Knowledge of the various wildcards and their combinations will significantly increase your productivity.