command jq

info

1. is a lightweight and flexible command line json processor

   1. jq is like sed for json data

       use it to slice and filter and map and transform
      

   2. written in portable c

       has zero runtime dependencies
      

tutorial

1. use github json api

   1. get last 5 commits from the jq repo

       $ curl 'https://api.github.com/repos/stedolan/jq/commits?per_page=5'
      

   2. the simplest jq program is the expression .

       $ curl 'https://api.github.com/repos/stedolan/jq/commits?per_page=5' | jq '.'
      

   3. extract just the first commit

       $ curl 'https://api.github.com/repos/stedolan/jq/commits?per_page=5' | jq '.[0]'
      

   4. leave out the curl command

       $ ... | jq '.[0] | {message: .commit.message, name: .commit.committer.name}'
      
       # the | operator in jq feeds output of one filter `.[0]`
       # into the input of another `{...}`
       # you can access nested attributes, such as `.commit.message`
      

   5. get the rest of the commits

       $ ... | jq '.[] | {message: .commit.message, name: .commit.committer.name}'
      
       # `.[]` returns each element of the array returned in the response, one at a time
       # which are all fed into `{message: .commit.message, name: .commit.committer.name}`
      
       # data in jq represented as streams of json values
       # streams are serialised by just separating json values with whitespace
       # this is a `cat` friendly format
       # join 2 json streams together and get a valid json stream
      

   6. get output as a single array

       $ ... | jq '[.[] | {message: .commit.message, name: .commit.committer.name}]'
      

   7. pull out all of the html_url fields inside that array of parent commits

       # and make a simple list of strings
       # to get along with the `message` and `author` fields
      
       $ ... | jq '[.[] | {message: .commit.message, name: .commit.committer.name, parents: [.parents[].html_url]}]'
      

manual