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Wild cards are a way of specifying one or more files using a
pattern. When you type in a command the shell will search for
the characters '*', '?', '{', '~' and '[' in
each word of the
command and its arguments. If one of the characters appears
then the word is regarded as a pattern and is replaced with
an alphabetically sorted list of file names that match the
pattern. Patterns are matched in the context of the given
word, that is, if a legal character is given as part of the
pattern, then the wild card attempts to match the file(s)
given the character's position within the pattern.
Some of the most common patterns are:
- '*', which matches any
number/sequence of characters (a string), including no
characters.
-
'?', which matches any single character.
- [...],
which matches any one of the characters enclosed by the
brackets (a pair of characters separated by a '-' matches any
characters between the pair).
-
{...}, like [...] except that
it works with a comma separated list of strings.
-
~username, which matches the home directory of the
given user (if the username is omitted, it matches your home
directory).
Note: A more complete
list of wildcards is also available.
Unlike DOS, where it is the command's responsibility to
perform wild card expansion, Unix lets the shell do the
expansion. So the Command "command a?" does not pass "a?" to
the command, rather, it passes however many files fit the
description of "a?" to the command; DOS commands would simply
get "a?" as the argument.
To make use of the wild cards above, the file must exist, or
the shell will report No match. However the {...}
pattern does not follow this convention; files that it
attempts to match do not have to exist, the result is simply
passed to the command.
Mixing of characters above are allowed (note: with the
exception of the '~', which must occur at the begining of
the pattern). You can use any combination of the above in a
single word or multiple words when using them. Another caveat
is that "dot" files (filenames that begin with a '.') are not
matched by wild cards unless the word explicitly begins with
a '.'.
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