CompTIA A+ Certification All-in-One Exam Guide

work with all command-line commands that take filenames. A great example
is the dir command. When you execute a plain dir command, it finds and
displays all the files and folders in the specified directory; however, you can
also narrow its search by adding a filename. For example, if you type the
command dir ailog.txt while in your root (C:\) directory, you get the
following result:
If you just want to confirm the presence of a particular file in a particular
place, this is very convenient. But suppose you want to see all files with the
extension .txt. In that case, you use the * wildcard, like this: dir *.txt. A good
way to think of the * wildcard is “I don’t care.” Replace the part of the
filename that you don’t care about with an asterisk (*). The result of dir *.txt
would look like this:
Wildcards also substitute for parts of filenames. This dir command will
find every file that starts with the letter a: