Wildcards

reading

Wildcards from the Linux Documentation Project.

When we want to match multiple files for an operation, we can use wildcards:

• * matches multiple (or 0) characters

• ? matches a single character

Let’s see how this works, by using the data in the ~/shell-lesson-data/exercise-data/alkanes directory.

If we do ls -l we should see:

total 24
-rw-rw----. 1 mzingale mzingale 1158 Apr 23  2025 cubane.pdb
-rw-rw----. 1 mzingale mzingale  622 Apr 23  2025 ethane.pdb
-rw-rw----. 1 mzingale mzingale  422 Apr 23  2025 methane.pdb
-rw-rw----. 1 mzingale mzingale 1828 Apr 23  2025 octane.pdb
-rw-rw----. 1 mzingale mzingale 1226 Apr 23  2025 pentane.pdb
-rw-rw----. 1 mzingale mzingale  825 Apr 23  2025 propane.pdb

This files contain information about the atomic structure of each compound (you can just use cat to look at one).

We can list all the files that start with p by doing:

ls p*

Here the * matches any number of characters. So both pentane.pdb and propane.pdb match.

We could instead look for all the 6-letter compounds that end in -ane by doing:

ls ???ane.pdb

Now, the ? matches exactly one character. By using 3 of them in a row, we are requiring 3 (and only 3) characters followed by ane.pdb in the filename.

Note

These wildcards, ? and *, are expanded by the shell first and then passed to the command we are using. This means that we can use them with any Unix commands.