Globbing is the process of expanding a non-specific file name containing a wildcard character into a set of specific file names that exist in storage on a computer, server, or network. A wildcard is a symbol that can stand for one or more characters. The most common wildcard symbols are the question mark (?) for a single character and the asterisk (*) for a contiguous string of characters.
Wildcards are useful when searching for expressions in which one or more of the characters can vary. An example is:
The result of this search is the set of all file names that exist in a given storage medium with William to the left of the period (such as William.txt, William.tif, William.doc, and so on). Wildcards are also useful when the spelling of a term or name is unknown. For example, if a user is unsure whether a person's first name is spelled as Philip or Phillip within a file name with the .rtf extension, the user can enter:Content Continues Below
Globbing often requires a computer or server to search huge numbers of files or directories, placing large demands on processing power and memory resources. This has led to denial-of-service (DoS) attacks by hackers who enter file names containing wildcards with the sole intention of causing a server to repeatedly and continuously glob (perform globbing functions). Vulnerability to this type of attack can be reduced by limiting the amount of time a server can spend globbing -- for example, limiting the wildcard input from specific users per unit time, or refusing to glob if a wildcard is too general.
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- The National Center for Supercomputing Applications (NCSA) at the University of Illinois (Champaign) offers some examples of globbing.