Once a JSON object is created, json-c functions are used to determine its data type and then specific functions are used to extract that data from the object, which is how JSON data is read in a C program. This video demonstrates how to extract data types and contents from JSON objects so that a C program can examine the JSON data.
- [Narrator] To read a specific value from JSON data, … you need to use the JSON-C library to create … a JSON object variable. … Next, you must know the element's name or key, … as well as the type of data stored. … This code searches the sample JSON data file, … named at line seven, looking for the key name, "lastName", … which is set at line eight. … The file is opened at line 13, with a JSON object variable … "jdata" holding the data. … Line 21 creates a JSON object for the named key, … which is saved in variable "objname", … the third argument in the function. … From this new object, the data type is determined … by the JSON object get type function, found at line 29. … Afterwards, a switch case structure is used … to output the type of data found. … I've already built and run the code, … so let's see what it does. … And the data type for last name, is a string. … To show the variety of data types in the sample document, … in this code, a while loop is found at line 25. … It processes all the entries at the top level, …
Author
Dan Gookin
Released
10/1/2019- Finding, installing, and linking libraries
- Accessing and generating XML data
- Working with JSON
- Working with the libcurl library
- Text programming
- Reading, writing, and manipulating JPEG images
- Working with PNG images
Skill Level Advanced
Duration
Views
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Introduction
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Using the exercise files1m 2s
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Working with the code2m 45s
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1. Setup and Configuration
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Understanding libraries2m 50s
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Finding a C library2m 44s
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Installing a library4m 15s
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Liking a library: IDE4m 10s
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2. Data Structures
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Understanding XML2m 23s
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Accessing XML data3m 26s
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Generating XML data3m 57s
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Working with JSON2m 39s
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Accessing JSON data3m 10s
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Reading JSON data3m 46s
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Creating JSON output3m 35s
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3. Web Access
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Testing libcurl2m 3s
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Fetching a web page3m 47s
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Saving web data3m 31s
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Sending data2m 35s
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4. Text Programming
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Working with wide characters3m 19s
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Building an ncurses program2m 27s
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Controlling the text screen2m 32s
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Making color text2m 56s
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Exploring ncurses input4m 6s
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5. Computer Graphics
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Accessing a JPEG2m 31s
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Manipulating JPEG images3m 5s
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Working with PNG images3m 57s
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Modifying a PNG image2m 26s
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Conclusion
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Writing your own library4m 19s
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Next steps1m 17s
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Video: Reading JSON data