The following table describes each regular expression that can be used to establish a pattern that results in a custom filter or node search must match.
| Name | Symbol | Description |
|---|---|---|
| Any Character | . | Any single character. |
| Character in Range | [] | Any character inside the brackets. For example, the expression [abc123] allows only any of the following characters: "a," "b," "c," "1," "2," or "3." |
| Character Not in Range | [^] | Any single character except for those inside the brackets. For example, the expression [^abc123] allows only any character except for: "a," "b," "c," "1," "2," or "3." |
| Range Character | [-] | Any single character contained within the specified range. For example, the expression [0-9] allows only any number that falls between 0 and 9. |
| Beginning of Input | ^ | Requires the expression that follows it at the beginning of the user-defined value. For example, the expression ^[abc123] allows only field data that starts with either "a," "b," "c," "1," "2," or "3." |
| End of Input | $ | Requires the expression that precedes it at the end of the user-defined value. For example, the expression [abc123]$ allows only field data that ends with either "a," "b," "c," "1," "2," or "3." |
| Not | ! | Requires that the expression following the symbol (!) not be found in the field data. For example, the expression a!b allows only field data containing an "a" when it is not immediately followed by "b." |
| Or | | | Requires one of two expressions. For example, the expression he|she allows only field data that is set to either "he" or "she." |
| 0 or More | * | The preceding expression can occur zero or more times. For example, the expression [0-9]* allows any set of consecutive digits or no digits at all. |
| 1 or More | + | The preceding expression can occur one or more times. For example, the expression [0-9]+ allows any set of consecutive digits. |
| Previous Statement is Optional | ? | The preceding expression is optional. Data satisfying the expression may be specified as field data or a user can choose to not enter it. For example, the expression [0-9][0-9]? allows only a single or double digit. |
| Group | () | Groups an expression together. For example, the expression (t|T)he allows only field data that is set to either "the" or "The". |
| Escape Character | \ | Either an abbreviation (see table below) or that the next character be translated literally. This character should only be used for reserved characters, such as those listed under the Symbol column of this table. For example, \d+ allows only one or more digits, while \d\+ allows a digit followed by a plus sign. |
Character Classes
A character class can be used to restrict the character for a particular field.
| Name | Symbol | Description |
|---|---|---|
| Alphanumeric | [[:alnum:]] | Any alphanumeric character. |
| Alphabetic | [[:alpha:]] | Any alphabetical character in the following ranges: a-z and A-Z. |
| Space/Tab | [[:blank:]] | A space or a tab. |
| Digit | [[:digit:]] | Any digit. A valid character is a whole number from 0 to 9. |
| Lower-case | [[:lower:]] | Any lower-case character (i.e., a-z). |
| Printable | [[:print:]] | Any printable character. |
| Punctuation | [[:punct:]] | Any punctuation character. |
| Space | [[:space:]] | Any whitespace character. |
| Upper-case | [[:upper:]] | Any upper-case character (i.e., A-Z). |
| Hexadecimal | [[:xdigit:]] | Any hexadecimal digit (i.e., 0-9, a-f and A-F). |
| Word | [[:word:]] | Any word character. Valid characters are all alphanumeric characters and underscore. |
Abbreviations
The following table describes the various abbreviations for specifying a regular expression.
| Name | Symbol | Description |
|---|---|---|
| Character | . | Any single character. |
| Decimal Digit | \d | Any single decimal digit. Corresponding syntax: [[:digit:]] |
| Non-Decimal Digit | \D | Any character except for a single decimal digit. Corresponding syntax: [^[:digit:]] |
| Lower-case | \l | Any lower-case character. Corresponding syntax: [[:lower:]] |
| Non-Lower-case | \L | Any character except for a lower-case character. Corresponding syntax: [^[:lower:]] |
| Space | \s | A single space character. Corresponding syntax: [[:space:]] |
| Non-Space | \S | Any character except for a single space character. Corresponding syntax: [^[:space:]] |
| Upper-case | \u | Any upper-case character. Corresponding syntax: [[:upper:]] |
| Non-Upper-case | \U | Any character except for an upper-case character. Corresponding syntax: [^[:upper:]] |