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Comparison Expressions

comparison expression { statements }

Comparison expression patterns allow variable values to be compared with other variables, constants, or regular expressions.

Comparison expressions are composed of a variable followed by a comparison operator, followed by another variable, constant, or regular expression. They are used to test variable content in place of pattern matching. A simple variable or a comparison expression with a value of the null string "" or 0 evaluates to FALSE and with any other value evaluates to TRUE.

CXL Comparison Operators used in Comparison Expression Patterns

String Matching Operators

~ contains

!~ does not contain

Relational Operators

== is equal to

!= is not equal to

> is greater than

>= is greater than or equal to

< is less than

<= is less than or equal to

|| or

&& and

When using ~ and !~ string-matching operators, always code the constant regular expression on the right-hand side of the operator. For example, $0(1 6) ~ /word/ would match the literal "word" appearing within the first through sixth characters of the input line.

The logical operators | | and && are used to combine expressions and evaluate as follows:

Combination Expressions and Their Results

Expression | x | | y | x & & y |
---|---|---|

x is true y is true | TRUE | TRUE |

x is true y is false | TRUE | FALSE |

x is false y is true | TRUE | FALSE |

x is false y is false | FALSE | FALSE |

The && operator takes precedence over || when both are used in a single expression.

Example

There are 3 true results for the if statement below, $1, $2 and $3 both, and $4.

if ( $1 || $2 && $3 || $4 ) accept $*;