Examining JSON with JQ

In this talk I show how to examine JSON data using the jq command-line tool. Sample files are available at my blog at http://aijaz.net/2016/10/25/jq/

Transcript

1. Slide the First 1 — Aijaz Ansari at NSCoderChicago, 10/25/2016
2. Mythical Creatures 2 — Aijaz Ansari at NSCoderChicago, 10/25/2016
3. http://weknowyourdreams.com/images/unicorn/unicorn-04.jpg 3 — Aijaz Ansari at NSCoderChicago, 10/25/2016
4. https://shellback0608.files.wordpress.com/2016/07/bird-phoenix-flight-art-drawing.jpg 4 — Aijaz Ansari at NSCoderChicago, 10/25/2016
5. https://i.ytimg.com/vi/kKJQESF0qqk/maxresdefault.jpg 5 — Aijaz Ansari at NSCoderChicago, 10/25/2016
6. API Docs 6 — Aijaz Ansari at NSCoderChicago, 10/25/2016
7. Exploring JSON With jq Aijaz Ansari @_aijaz_ 7 — Aijaz Ansari at NSCoderChicago, 10/25/2016
8. What is JSON? JavaScript Object Notation [ { "name": "Alice", "age": 20}, { "name": "Bob", "age": 30} ] 8 — Aijaz Ansari at NSCoderChicago, 10/25/2016
9. Reading JSON returned by remote servers @interface AAAJSONResponseSerializer : AFJSONResponseSerializer @end @implementation AAAJSONResponseSerializer - (id)responseObjectForResponse:(NSURLResponse *)response data:(NSData *)data error:(NSError *__autoreleasing *)error { #ifdef DEBUG NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *) response; NSString *body = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; DDLogInfo(@"RESPONSE BODY: %@", response.URL, body); DDLogInfo(@"RESPONSE: (%ld) %@ ", httpResponse.statusCode, response.URL); #endif // ... } @end 9 — Aijaz Ansari at NSCoderChicago, 10/25/2016
10. JSON Looks Like This [{"name":"Aang","sex":"M","born":-12,"died":153,"bending":["Air","Water","Earth","Fire","Energy"],"identity":{"nationality":"Southern Air Temple", "ethnicity":"Air Nomad"},"spouse":"Katara","children":[{"sex":"M","name":"Bumi"},{"sex":"F","name":"Kya"},{"sex":"M","name":"Tenzin"}]},{"name":"Katara","sex": "F","born":85,"died":null,"bending":["Water","Blood"],"identity":{"nationality":"Southern Water Tribe","ethnicity":"Water Tribe"},"spouse":"Aang","children":[{" sex":"M","name":"Bumi"},{"sex":"F","name":"Kya"},{"sex":"M","name":"Tenzin"}]},{"name":"Sokka","sex":"M","born":84,"died":164,"bending":[],"identity": {"nationality":"Southern Water Tribe","ethnicity":"Water Tribe"},"spouse":null,"children":[]},{"name":"Toph Beifong","sex":"F","born":88,"died":null,"bending": ["Earth","Metal"],"identity":{"nationality":"Gaoling, Earth Kingdom","ethnicity":"Earth Kingdom"},"spouse":null,"children":[{"sex":"F","name": "Lin Beifong"},{"sex":"F","name":"Suyin Beifong"}]},{"name":"Iroh","sex":"M","born":null,"died":null,"bending":["Fire","Energy"],"identity":{"nationality": "Fire Nation Capital, Fire Nation","ethnicity":"Fire Nation"},"spouse":null,"children":[{"sex":"M","name":"Lu Ten"}]},{"name":"Zuko","sex":"M","born":83, "died":null,"bending":["Fire","Energy"],"identity":{"nationality":"Fire Nation Capital, Fire Nation","ethnicity":"Fire Nation"},"spouse":null,"children": [{"sex":"F","name":"Izumi"}]},{"name":"Kya","sex":"F","born":null,"died":null,"bending":["Water"],"identity":{"nationality":"Southern Water Tribe","ethnicity": "Water Tribe, Air Nomad"},"spouse":null,"children":[]},{"name":"Bumi","sex":"M","born":null,"died":null,"bending":["Air"],"identity":{"nationality": "United Republic","ethnicity":"Water Tribe, Air Nomad"},"spouse":null,"children":[]},{"name":"Tenzin","sex":"M","born":null,"died":null,"bending":["Air"], "identity":{"nationality":"Republic City, United Republic","ethnicity":"Water Tribe, Air Nomad"},"spouse":null,"children":[{"sex":"F","name":"Jinora"},{"sex": "F","name":"Ikki"},{"sex":"M","name":"Meelo"},{"sex":"M","name":"Rohan"}]},{"name":"Lin Beifong","sex":"F","born":120,"died":null,"bending":["Earth","Metal"], "identity":{"nationality":"Republic City, United Republic","ethnicity":"Earth Kingdom"},"spouse":null,"children":[]},{"name":"Suyin Beifong","sex":"F","born": 126,"died":null,"bending":["Earth","Metal"],"identity":{"nationality":"Republic City, United Republic","ethnicity":"Earth Kingdom"},"spouse":null,"children": [{"sex":"M","name":"Bataar Jr."},{"sex":"F","name":"Opal"},{"sex":"M","name":"Wei"},{"sex":"M","name":"Wing"},{"sex":"M","name":"Huan"}]}] 10 — Aijaz Ansari at NSCoderChicago, 10/25/2016
11. jq Lightweight & Flexible Command-Line JSON Processor. https://stedolan.github.io/jq/ 11 — Aijaz Ansari at NSCoderChicago, 10/25/2016
12. Pretty Printing $ echo '[{"a": 1},{"b": 2}]' | jq . [ { "a": 1 }, { "b": 2 } ] $ If you remember only one thing about jq, let it be this, the '.' filter. 12 — Aijaz Ansari at NSCoderChicago, 10/25/2016
13. Filters → All jq programs are filters → A filter takes in input & produces output → 1 is the simplest filter: return 1 → . is the simplest useful filter: pretty print 13 — Aijaz Ansari at NSCoderChicago, 10/25/2016
14. Object Value Filter $ echo '{"a": 1, "b": 2, "c":3}' | jq .c 3 $ 14 — Aijaz Ansari at NSCoderChicago, 10/25/2016
15. Arrays $ echo '["a", "b", "c", "d", "e"]' | jq '.[2]' "c" $ echo '["a", "b", "c", "d", "e"]' | jq '.[1:4]' [ "b", "c", "d" ] $ 15 — Aijaz Ansari at NSCoderChicago, 10/25/2016
16. Iterators Read [] as foreach $ echo '["a", "b", "c", "d", "e"]' | jq '.[]' "a" "b" "c" "d" "e" $ Read .[] as iterating with an identity filter 16 — Aijaz Ansari at NSCoderChicago, 10/25/2016
17. Addition $ echo '["a", "b", "c", "d", "e"]' | jq '.[]+" hello"' "a hello" "b hello" "c hello" "d hello" "e hello" $ 17 — Aijaz Ansari at NSCoderChicago, 10/25/2016
18. Addition $ echo '["a", "b", "c", "d", "e"]' | jq '"hey "+ .[]+" hello"' "hey a hello" "hey b hello" "hey c hello" "hey d hello" "hey e hello" $ 18 — Aijaz Ansari at NSCoderChicago, 10/25/2016
19. Addition $ echo '[1,2,3,4,5]' | jq '.[]+10' 11 12 13 14 15 $ 19 — Aijaz Ansari at NSCoderChicago, 10/25/2016
20. Collecting Results Into an Array $ echo '[1,2]' | jq '.[]+10' 11 12 $ echo '[1,2]' | jq '[.[]+10]' [ 11, 12 ] 20 — Aijaz Ansari at NSCoderChicago, 10/25/2016
21. Filters can be piped with | 21 — Aijaz Ansari at NSCoderChicago, 10/25/2016
22. Creating Objects $ echo '[{"a": 1, "b": 2, "c": 3}, {"a": 10, "b": 20, "c": 30}]' | jq '.[]' { "a": 1, "b": 2, "c": 3 } { "a": 10, "b": 20, "c": 30 } $ 22 — Aijaz Ansari at NSCoderChicago, 10/25/2016
23. Creating Objects $ echo '[{"a": 1, "b": 2, "c": 3}, {"a": 10, "b": 20, "c": 30}]' | jq '.[]|{a,c}' { "a": 1, "c": 3 } { "a": 10, "c": 30 } $ If you remember only 2 things about jq, let this be the second: extracting just the keys you care about. 23 — Aijaz Ansari at NSCoderChicago, 10/25/2016
24. Creating Objects $ echo '[{"fn": "Ann", "ln": "Smith"},{"fn": "Ted", "ln": "Jones"}]' \ \ | jq '.[]|{"first": .fn, "last": .ln}' { "first": "Ann", "last": "Smith" } { "first": "Ted", "last": "Jones" } $ 24 — Aijaz Ansari at NSCoderChicago, 10/25/2016
25. Creating Objects $ echo '[{"fn": "Ann", "ln": "Smith"},{"fn": "Ted", "ln": "Jones"}]' \ \ | jq '.[]|{(.fn): .ln}' { "Ann": "Smith" } { "Ted": "Jones" } $ 25 — Aijaz Ansari at NSCoderChicago, 10/25/2016
26. Functions keys $ echo '[{"a": 1, "b": 2, "c": 3}, {"a": 10, "b": 20, "c": 30}]' | jq '.[]|keys' [ "a", "b", "c" ] [ "a", "b", "c" ] $ If you remember only 3 things about jq, let this be the third: examining keys. 26 — Aijaz Ansari at NSCoderChicago, 10/25/2016
27. Functions length $ echo '[{"a": 1, "b": 2, "c": 3}, {"a": 10, "b": 20, "c": 30}]' | jq '.[]|length' 3 3 $ 27 — Aijaz Ansari at NSCoderChicago, 10/25/2016
28. Functions map $ echo '[1,2,3,4,5]' | jq 'map(.+10)' [ 11, 12, 13, 14, 15 ] map(x) is equivalent to [.[] | x] 28 — Aijaz Ansari at NSCoderChicago, 10/25/2016
29. Addition $ echo '[1,2,3,4,5]' | jq '.[]+10' 11 12 13 14 15 $ 29 — Aijaz Ansari at NSCoderChicago, 10/25/2016
30. Addition $ echo '[1,2,3,4,5]' | jq '[.[]+10]' [ 11, 12, 13, 14, 15 ] $ 30 — Aijaz Ansari at NSCoderChicago, 10/25/2016
31. Functions map $ echo '[1,2,3,4,5]' | jq 'map(.+10)' [ 11, 12, 13, 14, 15 ] 31 — Aijaz Ansari at NSCoderChicago, 10/25/2016
32. Functions reduce $ echo '[1,2,3,4,5]' | jq 'reduce .[] as $i (0 ; . + $i)' 15 $ Somewhat equivalent to: $i = 0 for var in .[] { $i = $var + $i } 32 — Aijaz Ansari at NSCoderChicago, 10/25/2016
33. More Functions → has("foo") → in({"a": "b"}) → echo '[1,2,3]' | jq 'map(.+2)' # [3,4,5] → select(func) - like grep where func is true → ... and a whole lot more 33 — Aijaz Ansari at NSCoderChicago, 10/25/2016
34. Detailed Examples With Real Data 34 — Aijaz Ansari at NSCoderChicago, 10/25/2016
35. Sample JSON Body (sample.json) [{"name":"Aang","sex":"M","born":-12,"died":153,"bending":["Air","Water","Earth","Fire","Energy"],"identity":{"nationality":"Southern Air Temple", "ethnicity":"Air Nomad"},"spouse":"Katara","children":[{"sex":"M","name":"Bumi"},{"sex":"F","name":"Kya"},{"sex":"M","name":"Tenzin"}]},{"name":"Katara","sex": "F","born":85,"died":null,"bending":["Water","Blood"],"identity":{"nationality":"Southern Water Tribe","ethnicity":"Water Tribe"},"spouse":"Aang","children":[{" sex":"M","name":"Bumi"},{"sex":"F","name":"Kya"},{"sex":"M","name":"Tenzin"}]},{"name":"Sokka","sex":"M","born":84,"died":164,"bending":[],"identity": {"nationality":"Southern Water Tribe","ethnicity":"Water Tribe"},"spouse":null,"children":[]},{"name":"Toph Beifong","sex":"F","born":88,"died":null,"bending": ["Earth","Metal"],"identity":{"nationality":"Gaoling, Earth Kingdom","ethnicity":"Earth Kingdom"},"spouse":null,"children":[{"sex":"F","name": "Lin Beifong"},{"sex":"F","name":"Suyin Beifong"}]},{"name":"Iroh","sex":"M","born":null,"died":null,"bending":["Fire","Energy"],"identity":{"nationality": "Fire Nation Capital, Fire Nation","ethnicity":"Fire Nation"},"spouse":null,"children":[{"sex":"M","name":"Lu Ten"}]},{"name":"Zuko","sex":"M","born":83, "died":null,"bending":["Fire","Energy"],"identity":{"nationality":"Fire Nation Capital, Fire Nation","ethnicity":"Fire Nation"},"spouse":null,"children": [{"sex":"F","name":"Izumi"}]},{"name":"Kya","sex":"F","born":null,"died":null,"bending":["Water"],"identity":{"nationality":"Southern Water Tribe","ethnicity": "Water Tribe, Air Nomad"},"spouse":null,"children":[]},{"name":"Bumi","sex":"M","born":null,"died":null,"bending":["Air"],"identity":{"nationality": "United Republic","ethnicity":"Water Tribe, Air Nomad"},"spouse":null,"children":[]},{"name":"Tenzin","sex":"M","born":null,"died":null,"bending":["Air"], "identity":{"nationality":"Republic City, United Republic","ethnicity":"Water Tribe, Air Nomad"},"spouse":null,"children":[{"sex":"F","name":"Jinora"},{"sex": "F","name":"Ikki"},{"sex":"M","name":"Meelo"},{"sex":"M","name":"Rohan"}]},{"name":"Lin Beifong","sex":"F","born":120,"died":null,"bending":["Earth","Metal"], "identity":{"nationality":"Republic City, United Republic","ethnicity":"Earth Kingdom"},"spouse":null,"children":[]},{"name":"Suyin Beifong","sex":"F","born": 126,"died":null,"bending":["Earth","Metal"],"identity":{"nationality":"Republic City, United Republic","ethnicity":"Earth Kingdom"},"spouse":null,"children": [{"sex":"M","name":"Bataar Jr."},{"sex":"F","name":"Opal"},{"sex":"M","name":"Wei"},{"sex":"M","name":"Wing"},{"sex":"M","name":"Huan"}]}] http://aijaz.net/2016/10/25/jq/ 35 — Aijaz Ansari at NSCoderChicago, 10/25/2016
36. http://feelgrafix.com/data_images/out/28/973590-avatar-the-last-airbender.jpg Example data of characters from the 'Avatar' series. 36 — Aijaz Ansari at NSCoderChicago, 10/25/2016
37. # Pretty print the jq $ cat sample.json | jq '.' ... { "sex": "M", "name": "Huan" } ] } ] $ # The ']' on the last line tells me this is an array # The '}' on the 2nd-last line tells me this is an array of objects # From now on, for space reasons, # 'cat sample.json ' will be abbreviated to 'cj' 37 — Aijaz Ansari at NSCoderChicago, 10/25/2016
38. # Just show me the first object $ cj | jq '.[0]' 38 — Aijaz Ansari at NSCoderChicago, 10/25/2016
39. # Show me an object with the name and # sex of the first object $ cj | jq '.[0]|{name, sex}' { "name": "Aang", "sex": "M" } $ 39 — Aijaz Ansari at NSCoderChicago, 10/25/2016
40. # Show me all the keys of each object $ cj | jq '.[]|keys' ... [ "bending", "born", "children", "died", "identity", "name", "sex", "spouse" ] $ 40 — Aijaz Ansari at NSCoderChicago, 10/25/2016
41. # Show me all the number of keys of each object $ cj | jq '.[]|length' # same as .[]|keys|length 8 8 8 8 8 8 8 8 8 8 8 $ 41 — Aijaz Ansari at NSCoderChicago, 10/25/2016
42. # The name of each character $ cj | jq '.[].name' "Aang" "Katara" "Sokka" "Toph Beifong" "Iroh" "Zuko" "Kya" "Bumi" "Tenzin" "Lin Beifong" 42 — Aijaz Ansari at NSCoderChicago, 10/25/2016
43. # The number of records $ cj | jq '[.[]]|length' 11 $ 43 — Aijaz Ansari at NSCoderChicago, 10/25/2016
44. # All female characters $ cj | jq '.[]|select(.sex == "F")' 44 — Aijaz Ansari at NSCoderChicago, 10/25/2016
45. # The names of all female characters # Take the resulting objects, put thmm in an array # Then iterate over that array, printing the name $ cj | jq '[.[]|select(.sex == "F")]|.[].name' "Katara" "Toph Beifong" "Kya" "Lin Beifong" "Suyin Beifong" $ 45 — Aijaz Ansari at NSCoderChicago, 10/25/2016
46. # The name of all members of the Fire Nation # You can drill down objects with multiple .s # e.g.: .identity.ethnicity $ cj | jq '[.[]|select(.identity.ethnicity == "Fire Nation")]|.[].name' "Iroh" "Zuko" 46 — Aijaz Ansari at NSCoderChicago, 10/25/2016
47. # The name and bending list of all characters who can bend Fire # Similar to previous example: iterate, select, construct a list, iterate on that list, # and extract the name and bending fields $ cj | jq -c '[.[]|select(.bending[]|select(contains("Fire")))]|.[]|{name, bending}' {"name":"Aang","bending":["Air","Water","Earth","Fire","Energy"]} {"name":"Iroh","bending":["Fire","Energy"]} {"name":"Zuko","bending":["Fire","Energy"]} $ 47 — Aijaz Ansari at NSCoderChicago, 10/25/2016
48. # Similar to previous, but make the name be the key of the object $ cj | jq -c '[.[]|select(.bending[]|select(contains("Fire")))]|.[]|{(.name): .bending}' {"Aang":["Air","Water","Earth","Fire","Energy"]} {"Iroh":["Fire","Energy"]} {"Zuko":["Fire","Energy"]} 48 — Aijaz Ansari at NSCoderChicago, 10/25/2016
49. # Names and firstborns of each character, as hashes in an array $ cj | jq '[.[]|{name, firstBorn: .children[0].name}]' 49 — Aijaz Ansari at NSCoderChicago, 10/25/2016
50. # How many children does each person have? $ cj | jq '[.[]|.name, (.children|length)]' [ { "Aang": 3 }, { "Katara": 3 }, ... { "Suyin Beifong": 5 } ] $ 50 — Aijaz Ansari at NSCoderChicago, 10/25/2016
51. # List of each person, along with the number of their children # Essentially, merging the array of objects from the previous example into 1 big object $ cj | jq '[.[]|[.name, (.children|length)]] | reduce .[] as $i ({}; . + { ($i[0]): $i[1]} )' { "Aang": 3, "Katara": 3, "Sokka": 0, "Toph Beifong": 2, "Iroh": 1, "Zuko": 1, "Kya": 0, "Bumi": 0, "Tenzin": 4, "Lin Beifong": 0, "Suyin Beifong": 5 } $ 51 — Aijaz Ansari at NSCoderChicago, 10/25/2016
52. # Take the object matrix from two slides ago, and transpose it $ cj | jq '[.[]|[.name, (.children|length)]] | transpose' [ [ "Aang", "Katara", "Sokka", "Toph Beifong", ... "Suyin Beifong" ], [ 3, 3, 0, 2, ... 5 ] ] $ 52 — Aijaz Ansari at NSCoderChicago, 10/25/2016
53. Three Most Useful Filters '.' # Pretty print '.[]|{a, b}' # Extract just the a and b keys from each object '.[]|keys' # Display the keys of each object in the array Honorable Mention '[.[]|select(C)]' # Return an array of only those objects where condition C is true 53 — Aijaz Ansari at NSCoderChicago, 10/25/2016
54. Resources → jq: https://stedolan.github.io/jq/ → jq manual: https://stedolan.github.io/jq/manual/ → Sample JSON file: http://aijaz.net/2016/10/25/jq/ 54 — Aijaz Ansari at NSCoderChicago, 10/25/2016
55. Thanks! 55 — Aijaz Ansari at NSCoderChicago, 10/25/2016