Version 15 of wild cards

In a shell environment, the term wild cards refers to metacharacters that are then expanded (also referenced as globbed) into a series of file names.

See glob for a Tcl function which provides some wild card expansion.

One concept that is sometimes hard for people to grasp is that wild cards are often handled transparently to the user.

That is to say, on Unix, before a command ever sees a command line from a shell, the shell has expanded the wild cards into file names.

However, other shells, such as Tcl, do not do such wild card expansions automatically. The programmer of an application is responsible to either expand them (via glob) or to invoke an external command which then expands the wild cards.

Glob-style wild-card characters

* matches any string of characters (including the empty string)

ab*cd: Matches a string with ab at the start and cd at the end

? matches any single character.

ab?cd: Matches a string 5 characters long with ab at the start and cd at the end.

[...] matches a set of characters (need more detail)

ab[cd]: Matches a string 3 characters long starting with ab followed by c or d
ab[c-e]f: Matches a string 4 characters long starting with ab, followed by a c, d or e and with an f at the end.

{alt1,alt2} matches alternatives (but not in [string match]) (Wiki bug: can't have unbalanced braces inside font context, so alt1 and alt2 are erroneously bold.)

   ab{c,?c}d   Matches any string 4 or 5 characters long with ''ab'' at the start and ''cd'' at the end.

\\ forces the next character to be interpreted as a literal. (Wiki bug: single backslash causes crash.)

a\*c: Matches precisely the string a*c character