Globbing

What is commonly referred to as globbing is a simple pattern matching language.

Command line shells on Linux systems use this language to refer to groups of files whose names match a specific pattern. There are three pattern matching characters:

Character	Description
`*`	Matches any number of any character, including no characters.
`?`	Matches any one character.
`[]`	Matches a class of characters.
	- Matches a range of characters
	- `^` Negates the matching of characters.

Important

This means that you can tell your shell to match a pattern instead of a literal string of text.

Match any number of any character

$ cd ~/linux_essentials-2.4/globs 
$ ls question1 question14 question2012 star10 star2002 question13 question15 question23 star1100 star2013 
$ ls star1* 
star10 star1100 
$ ls star* 
star10 star1100 star2002 star2013 
$ ls star2* 
star2002 star2013 
$ ls star2*2 
star2002

The * character expands to any number of anything. The first example prints all files starting with star1, this results in start10 and star1100.

Match any one character

$ ls 
question1 question14 question2012 star10 star2002 question13 question15 question23 star1100 star2013 
$ ls question? 
question1 
$ ls question1? 
question13 question14 question15 
$ ls question?3 
question13 question23 
$ ls question13? 
ls: cannot access question13?: No such file or directory

The ? character expands to any single character, in a fixed position.

Match a class of characters

The [] brackets are used to match ranges or classes of characters. The [] brackets work like they do in POSIX regular expressions except with globs the ^ is used instead of !.

The character classes supported depends on your current locale. POSIX requires the following character classes for all locales:

`[:alnum:]`	Letters and numbers.
`[:alpha:]`	Upper or lowercase letters.
`[:blank:]`	Spaces and tabs.
`[:cntrl:]`	Control characters, e.g. backspace, bell, NAK, escape.
`[:digit]`	Numerals (0123456789).
`[:graph:]`	Graphic characters (all characters except `ctrl` and the space character).
`[:lower:]`	Lowercase letters (`a-z`).
`[:print:]`	Printable characters (`alnum`, `punct`, and the space character).
`[:punct:]`	Punctuation characters, i.e. `!`, &, `"`.
`[:space:]`	Whitespace characters, e.g. tabs, spaces, newlines.
`[:upper:]`	Uppercase letters (`A-Z`)
`[:xdigit:]`	Hexadecimal numerals (usually `0123456789abcdefABCDEF`).

To use the digit class, you would do something like this:

$ ls file[[:digit:]]
file1 file2 file3 file4 file5 file6 file7

To match the string file followed by a digit or a, it would look something like this:

$ ls file[[:digit:]a]
file1 file2 file3 file4 file5 file6 file7 filea

In contrast, to match a string file followed by a digit and then an a, it would look something like this:

$ ls file[[:digit:]]a
file1a