To use this transformer to parse out portions of an input attribute, "subexpressions" within the regular expression are used. Subexpressions are enclosed in parentheses ( ), and the portion of the input text that matched that subexpression is stored as an entry in the “Matched Parts Attribute” list. The elements of this list can then be exposed to Workbench by right clicking on it and indicating the number of elements to expose for later use. See below for some examples.
Advanced Regular Expressions (AREs) are supported. For a complete description of AREs, see Syntax of Tcl Regular Expressions in the FME Functions and Factories manual, or see Regular Expression Information.
In brief, an ARE is one or more branches, separated by |, matching anything that matches any of the branches.
A brief summary of the special characters and their meanings is:
| | | separates "branches" (or choices) |
| * | a sequence of 0 or more matches of what precedes it |
| + | a sequence of 1 or more matches of what precedes it |
| ? | a sequence of 0 or 1 matches of what precedes it |
| . | matches any single character |
| ^ | matches the start of the value |
| $ | matches the end of the value |
| [ ] | enclose a set of character choices |
| ( ) | enclose a "subexpression" -- whatever matches each subexpression is placed into the “Matched Parts Attribute”{} list attribute |
| a | any character can be listed to be matched |
Examples:
| ^A | matches any value starting with an A |
| ^[0-9] | matches any value starting with a digit |
| ^[0-9]+$ | matches any value consisting exclusively of digits |
| ^(beef|chicken)$ | matches values of either “beef” or “chicken” |
| ^([0-9]*) ([0-9]*)$ | matches two integer numbers separated by a space, and puts the first number into “Matched Parts Attribute”{0} and the second into “Matched Parts Attribute”{1} |
| ^N([0-9][0-9])[.]([0-9][0-9])[.]([0-9][0-9]) | matches N23.45.11 and puts 23 into “Matched Parts Attribute”{0}, 45 into “Matched Parts Attribute”{1}, and 11 into “Matched Parts Attribute”{2} |
The Regular Expression field can also include any number of special characters.
Characters can be expressed as regular characters but they can also include any number of control characters.
Special character sequences (Advanced Editor only) are interpreted as shown below:
| Sequence | Description |
|---|---|
|
Ctrl+Shift+g (^G) |
Audible alert (bell) (0x07) |
|
Ctrl+Shift+h (^H) |
Backspace (0x08) |
|
Ctrl+Shift+l (^L) |
Form feed (0x0c) |
|
Ctrl+Shift+j (^J) |
Newline (0x0a) |
|
Ctrl+Shift+r (^M) |
Carriage return (0x0d) |
|
Ctrl+Shift+i (^I) |
Tab (0x09) |
|
Ctrl+Shift+k (^K) |
Vertical tab (0x0b) |
|
\ |
Backslash |
Defining Special Characters
You can define special characters through the Basic or Advanced Editors. Click Open Editor from the parameter menu:
Basic Text Editor
Select Constant from the String Type column (or, in some transformers, the Value column) and click on the empty field in the column:
Click the browse button to the right of the column to open an Edit Value dialog. In this editor, enter characters using the shortcut keys from the table above.
Note: To see tab characters, click the Options menu on the bottom left and select Show Spaces/Tabs.
Advanced Text Editor
Enter characters using the shortcuts from the table above.
Note: To see tab characters, click the Options menu on the bottom left and select Show Spaces/Tabs.