Regular expression
A Regular expression is a text pattern that describes how textual input should be parsed to retrieve a piece (or complete) of the textual input.
For regular expression we advise, to learn on how to use regular expressions, at a dedicated internet site. For example: https://www.regular-expressions.info/tutorial.html
An online regular expression tester can also be used to verify the correctness of the regular expression: https://regex101.com/
Configurable device drivers[edit]
In RadiMation® the Regular expressions are often used to interpret the response of a device. Several configurable device drivers, provide a possibility to specify the regular expression to convert the response on a query-command into a value.
The most complete regular expression to retrieve a floating point number from a response is:
([+-]?[0-9]*\.?[0-9]+([eE][+-]?[0-9]+)?)
The part of the regular expression that is included within the outermost brackets is taken as the final result.
Regular expression examples[edit]
Some examples for interpreting a response are:
| Received information | Regular expression | Determined measurement value | Note |
|---|---|---|---|
| U_L_N 325 | (-?[0-9.,Ee-]+) | 325 | Takes the first number. |
| I_L1;12.34 | ;(-?[0-9.,Ee-]+) | 12.34 | Takes the first number after ";". |
| THD_U_L1;;14,5 | ;;(-?[0-9.,Ee-]+) | 14.5 | Takes the first number after ";;". |
| AC_FREQ;Channel1;1.23E3 | ;.*;(-?[0-9.,Ee-]+) | 1230 | Takes the first number after the appearance of a second ";". |
The correctness of the regular expression can be tested, verified and improved by using the Validate Expression tool within the configurable device driver.
Links[edit]
- Wikipedia: Regular Expression
- Regular expression tutorial: http://www.regular-expressions.info/tutorial.html
- Regular epxression tester: https://regex101.com/