
\S expression:  regular expression:  full regular expression:  limited\S
\Sregular expression:  logical expression:  logical operator:  pattern\S
\Smatching \S

An expression is a series of characters that has value.  In UNIX the
values of expressions are most often "strings"\S*\S or the logical values
TRUE and FALSE.  Expressions that have string values are full regular
expressions, which are sometimes called regular expressions, and limited
regular expressions.  You create these expressions using alphanumeric
characters and "special characters"\S*\S.  Limited regular expressions
use a subset of the possible alphanumeric characters and special
characters.  In UNIX systems, these expressions are most often used with
commands to identify strings in a file.  The activity of finding strings
using expressions is called pattern matching.  For example, you might want
to search for strings that contain one or more occurrences of the letter
"a".  To do this you would use the regular expression "a+".  This
expression would match "a", "aa", and "aaaaaa".  The manual pages for
ed(1), grep(1), and egrep(1) contain more information on expressions and
pattern matching.

You create expressions with logical value using regular expressions in
combination with logical operations.  Logical operators are "&" for logical
"and", "|" for logical "or" and "!" for logical "not".  For example,
"a+|t+" would match any string that had any number of the character "a" or
the character "t".

\S*\S defined in the \Sglossary\S
