Unix Power ToolsUnix Power ToolsSearch this book

Chapter 33. Wildcards


File-Naming Wildcards
Filename Wildcards in a Nutshell
Who Handles Wildcards?
What if a Wildcard Doesn't Match?
Maybe You Shouldn't Use Wildcards in Pathnames
Getting a List of Matching Files with grep -l
Getting a List of Nonmatching Files
nom: List Files That Don't Match a Wildcard

33.1. File-Naming Wildcards

Wildcards (Section 1.13) are the shell's way of abbreviating filenames. Just as in poker, where a wildcard is a special card that can match any card in the deck, filename wildcards are capable of matching letters or groups of letters in the alphabet. Rather than typing a long filename or a long chain of filenames, a wildcard lets you provide parts of names and then use some "wildcard characters" for the rest. For example, if you want to delete all files whose names end in .o, you can give the following command:

% rm *.o

You don't have to list every filename.

I'm sure you already know that wildcards are useful in many situations. If not, they are summarized in Section 33.2. Here are a few of my favorite wildcard applications:

It's a common misconception, particularly among new users, that application programs and utilities have something to do with wildcards. Given a command like grep ident *.c, many users think that grep handles the * and looks to see which files have names that end in .c. If you're at all familiar with Unix's workings, you'll realize that this is the wrong picture. The shell interprets wildcards. That is, the shell figures out which files have names ending in .c, puts them in a list, puts that list on the command line, and then hands that command line to grep. As it processes the command line, the shell turns grep ident *.c into grep ident file1.c file2.c....

Since there are several shells, one might think (or fear!) that there should be several different sets of wildcards. Fortunately, there aren't. The basic wildcards work the same for all shells.

-- ML

Library Navigation Links

Copyright © 2003 O'Reilly & Associates. All rights reserved.