(gawk.info.gz) Leftmost Longest

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(gawk.info.gz) Case-sensitivity

(gawk.info.gz) Regexp

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 3.7 How Much Text Matches?
 ==========================
 
 Consider the following:
 
      echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }'
 
    This example uses the `sub()' function (which we haven't discussed
 yet;  String Functions) to make a change to the input record.
 Here, the regexp `/a+/' indicates "one or more `a' characters," and the
 replacement text is `<A>'.
 
    The input contains four `a' characters.  `awk' (and POSIX) regular
 expressions always match the leftmost, _longest_ sequence of input
 characters that can match.  Thus, all four `a' characters are replaced
 with `<A>' in this example:
 
      $ echo aaaabcd | awk '{ sub(/a+/, "<A>"); print }'
      -| <A>bcd
 
    For simple match/no-match tests, this is not so important. But when
 doing text matching and substitutions with the `match()', `sub()',
 `gsub()', and `gensub()' functions, it is very important.   String
 Functions, for more information on these functions.  Understanding
 this principle is also important for regexp-based record and field
 splitting ( Records, and also  Field Separators).
 

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(gawk.info.gz) Case-sensitivity

(gawk.info.gz) Regexp

(gawk.info.gz) Computed Regexps