(gawk.info) Pattern Summary

 
 Pattern Summary
 ---------------
 
    `awk' patterns may be one of the following:
 
      /REGULAR EXPRESSION/
      RELATIONAL EXPRESSION
      PATTERN && PATTERN
      PATTERN || PATTERN
      PATTERN ? PATTERN : PATTERN
      (PATTERN)
      ! PATTERN
      PATTERN1, PATTERN2
      BEGIN
      END
 
    `BEGIN' and `END' are two special kinds of patterns that are not
 tested against the input.  The action parts of all `BEGIN' rules are
 concatenated as if all the statements had been written in a single
 `BEGIN' rule.  They are executed before any of the input is read.
 Similarly, all the `END' rules are concatenated, and executed when all
 the input is exhausted (or when an `exit' statement is executed).
 `BEGIN' and `END' patterns cannot be combined with other patterns in
 pattern expressions.  `BEGIN' and `END' rules cannot have missing
 action parts.
 
    For `/REGULAR-EXPRESSION/' patterns, the associated statement is
 executed for each input record that matches the regular expression.
 Regular expressions are summarized below.
 
    A RELATIONAL EXPRESSION may use any of the operators defined below in
 the section on actions.  These generally test whether certain fields
 match certain regular expressions.
 
    The `&&', `||', and `!' operators are logical "and," logical "or,"
 and logical "not," respectively, as in C.  They do short-circuit
 evaluation, also as in C, and are used for combining more primitive
 pattern expressions.  As in most languages, parentheses may be used to
 change the order of evaluation.
 
    The `?:' operator is like the same operator in C.  If the first
 pattern matches, then the second pattern is matched against the input
 record; otherwise, the third is matched.  Only one of the second and
 third patterns is matched.
 
    The `PATTERN1, PATTERN2' form of a pattern is called a range
 pattern.  It matches all input lines starting with a line that matches
 PATTERN1, and continuing until a line that matches PATTERN2, inclusive.
 A range pattern cannot be used as an operand of any of the pattern
 operators.
 
     Pattern Elements Pattern Overview.
Info Catalog
(gawk.info) Rules Summary
(gawk.info) Regexp Summary
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