Many shell commands take one or more filenames as arguments. For example, to display the content of a text file named list.txt, the cat command would be used as follows:
$ cat list.txt
Similarly, the content of multiple text files could be displayed by specifying all the file names as arguments:
$ cat list.txt list2.txt list3.txt list4.txt
Instead of typing in each name, pattern matching can be used to specify all files with names matching certain criteria. For example, the ‘*’ wildcard character can be used to simplify the above example:
$ cat *.txt
The above command will display the content of all files ending with a .txt extension. This could be further restricted to any file names beginning with list and ending in .txt:
$ cat list*.txt
Single character matches may be specified using the ‘?’ character:
$ cat list?.txt