json2xml

Bash script that parses a JSON file into XML data.

Table of Contents

• Installation
• Usage
• Sample Output
• XML Name Handling
• Special Character Handling
• Error Handling
• Test Cases
• License
• References

Installation

Place json2xml.sh into desired location and make it executable with chmod +x json2xml.sh.

Usage

./json2xml.sh [options] json_file [xml_file]

Options

  -h      Show the help documentation
  -a      Append XML data to output file
  -i N    Set the indentation to N spaces (default: 4)
  -t      Use tab indentation instead of spaces
  -x      Omit the header from the XML data

Examples

./json2xml.sh -i 2 sample1.json
./json2xml.sh -t sample2.json output.xml
./json2xml.sh -atx sample3.json output.xml

Sample Output

JSON input

{
    "name": "Sleeping Kitty",
    "type": "wallpaper",
    "image": {
        "url": "images/kitty.jpg",
        "width": 1920,
        "height": 1080,
        "aspect ratio": 1.778
    },
    "thumbnail": {
        "url": "images/thumbnails/kitty.jpg",
        "width": 160,
        "height": 90
    },
    "metadata": {
        "created": "2025:02:11 11:34:47",
        "modified": "2025:05:09 21:36:21",
        "keywords": {
            "tag": [
                "cat",
                "kitten",
                "kitty",
                "sleeping",
                "wallpaper"
            ]
        }
    },
    "permissions": {
        "read": true,
        "write": false
    }
}

XML output

<?xml version="1.0" encoding="UTF-8"?>
<name>Sleeping Kitty</name>
<type>wallpaper</type>
<image>
    <url>images/kitty.jpg</url>
    <width>1920</width>
    <height>1080</height>
    <aspect_ratio>1.778</aspect_ratio>
</image>
<thumbnail>
    <url>images/thumbnails/kitty.jpg</url>
    <width>160</width>
    <height>90</height>
</thumbnail>
<metadata>
    <created>2025:02:11 11:34:47</created>
    <modified>2025:05:09 21:36:21</modified>
    <keywords>
        <tag>cat</tag>
        <tag>kitten</tag>
        <tag>kitty</tag>
        <tag>sleeping</tag>
        <tag>wallpaper</tag>
    </keywords>
</metadata>
<permissions>
    <read>true</read>
    <write>false</write>
</permissions>

XML Name Handling

While the XML specification permits a large group of Unicode symbol characters to be used in XML names, this script only permits the valid ASCII characters listed in the specification.

The first permitted character for an XML name must be an alphabetic character, a colon, or an underscore:

NameStartChar ::= [A-Z] | [a-z] | ":" | "_"

The remaining permitted characters for an XML name may be any valid character listed above, a digit, a hyphen, or a period:

NameChar ::= NameStartChar | [0-9] | "-" | "."

If the first character is not a valid NameStartChar, a leading underscore is added to the name. Any character encountered in the JSON property name that is not a NameStartChar or NameChar as defined above is skipped, except for spaces which are replaced with underscores to preserve the original formatting. If no valid characters are found, a generic name of element will be used for the XML name.

Special Character Handling

XML Character References

There are five special reserved characters in XML. When these characters are encountered in a JSON string value, they are replaced with their corresponding XML character reference:

Character	Reference	Name
<	&lt;	Less than sign
>	&gt;	Greater than sign
&	&amp;	Ampersand
"	&quot;	Quotation mark
'	&apos;	Apostrophe

JSON Control Characters

When the following three JSON control characters are encountered in a string value, they are replaced with their corresponding XML character reference:

Character	Reference	Name
\t			Horizontal Tab
\n	
	Line Feed
\r	
	Carriage Return

The following three JSON control characters do not require character references, so their corresponding values are added directly to the XML output. Note that a Unicode character is represented by the control character \u followed by four hexadecimal digits, as shown in the example below:

Character	Value	Name
\\	\	Reverse Solidus
\/	/	Solidus
\u0394	Δ	Unicode Character

The following two control characters are valid JSON control characters but have no valid XML equivalents and therefore are skipped:

Character	Name
\b	Backspace
\f	Line Feed

Error Handling

While parsing the input, the script will actively check for various syntax errors present in the JSON file. The following five conditions will trigger an error and terminate processing:

• An object value is missing a required , or }
• An array value is missing a required , or ]
• A property is missing a required : between the name and value
• A string value is missing a terminating "
• An invalid numerical value or literal name token was found

No XML data will be generated, and an error message will be output to stderr.

An example error message for an improperly terminated array:

./json2xml.sh: error in input file: ',' or ']' expected! (Line 36:9)

Test Cases

The following test cases are used to verify proper script operation:

• test_xml_names.json: XML Name Handling
• test_characters.json: Special Character Handling
• test_values.json: JSON Numerical Formats and Literals

The following test cases are used to verify proper error handling:

• error_object.json: Object missing terminating }
• error_array.json: Array missing separating ,
• error_colon.json: Property missing separating :
• error_string.json: String missing terminating "
• error_value.json: Numerical value is invalid

These test cases, along with their output results, can be found in the repository test cases folder.

License

GNU General Public License v3.0

References

ECMA-404 The JSON Data Interchange Standard

W3C Extensible Markup Language (XML) 1.0 (Fifth Edition)