This page is for anyone writing expressions, macros or scripts in which you need to escape special characters.
When writing expressions, macros or scripts you may need to enter a character that has special meaning. For example, a string could include a double-quote, but in the expression PhixFlow will read this as the end of the string. To tell PhixFlow to ignore a special character, you can use the backslash character.
| Character | Type | Escape string |
|---|---|---|
backspace | Represented As | "\b" |
| Escaped | "\\\\b" | |
| form feed | Represented As | "\f" |
| Escaped | "\\\\f" | |
| tab | Represented As | "\t" |
| Escaped | "\\\\t" | |
| carraige return | Represented As | "\r" |
| Escaped | "\\\\r" | |
| newline | Represented As | "\n" |
| Escaped | "\\\\n" | |
| backslash | Represented As |
|
| Escaped | "\\\\\\\\" | |
| double quote | Represented As | '"' |
| Escaped | '\\\\"' |
Macro: Escaping Invalid Characters
If you are outputting stream data into JSON format, the data can include special characters that JSON will not accept. The following macro escapes these invalid characters.
By way of understanding: \b is standard notation for the backspace character. However, \ is also a special character in JSON, so we need to escape this with \\\\ to tell it that the \ should not be treated as a special character in this instance.
do(
$value = $args[1],
$value = replaceAll( $value , "\b","\\\\b"),
$value = replaceAll( $value , "\f","\\\\f"),
$value = replaceAll( $value , "\t","\\\\t"),
$value = replaceAll( $value , "\r","\\\\r"),
$value = replaceAll( $value , "\n","\\\\n"),
$value = replaceAll( $value , "\\\\","\\\\\\\\"),
$value = replaceAll( $value , '"','\\\\"')
)
Un-escape Macro. This is useful when importing JSON into PhixFlow from an external source. Once JSON has been converted to XML (jsonToXML), and XML converted to Items (xmlToItems) it converts any escaped sequence (eg \\\\t) back into a usable character. The double \\ ahead of the \t in the output is necessary to escape \t when the jep expression is passed and will be converted to simply \t (the tab character).
do(
$value= $args[1],
$value = replaceAll($value, "\\\\t","\\\t"),
$value = replaceAll($value, "\\\\b","\\\b"),
$value = replaceAll($value, "\\\\r","\\\r"),
$value = replaceAll($value, "\\\\n","\\\n"),
$value = replaceAll($value, "\\\\f","\\\f"),
$value
)
Check the format of the JSON you are importing to see what adjustments are required. Sometimes characters such as \\\\\\\\" may be helpfully un-escaped prior to import, making it unnecessary to unescape every special character.
Validating Data Imported Into PhixFlow
JSON data (like any imported data format) can include characters that cannot be written to a database that is using the UTF-8 character set. For example, 4-bit Emojis are not supported by UTF-8.
The following regular expression lists the characters expected in a JSON file and removes invalid characters from it.
replaceAll(JSON Code,"[^\\p{Space}0-9A-Za-z!:\\\"%&\\[*()\\],-/_\\\\{}\\.]","")
The backslash character escapes special characters such as [] , . and \
Check which database PhixFlow is running on to see how it handles 4-bit characters. An oracle database with the recommended configuration can store the full range of Uni-code characters whilst MySQL/MariaDB UFT-8mb3 databases cannot and invalid characters will need to be removed before writing to the database. See Database for recommended database configurations.
See also: Regular Expressions