brew.sh

$ brew install jq

curl.sh

$ curl "http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola"

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE eSearchResult PUBLIC "-//NLM//DTD esearch 20060628//EN" "http://eutils.ncbi.nlm.nih.gov/eutils/dtd/20060628/esearch.dtd">
<eSearchResult><Count>2819</Count><RetMax>20</RetMax><RetStart>0</RetStart><IdList>
<Id>25587816</Id>
<Id>25585832</Id>
...
<Id>25580233</Id>
</IdList><TranslationSet><Translation>     <From>ebola</From>     <To>"hemorrhagic fever, ebola"[MeSH Terms] OR ("hemorrhagic"[All Fields] AND "fever"[All Fields] AND "ebola"[All Fields]) OR "ebola hemorrhagic fever"[All Fields] OR "ebola"[All Fields] OR "ebolavirus"[MeSH Terms] OR "ebolavirus"[All Fields]</To>    </Translation></TranslationSet><TranslationStack>   <TermSet>    <Term>"hemorrhagic fever, ebola"[MeSH Terms]</Term>    <Field>MeSH Terms</Field>    <Count>1033</Count>    <Explode>Y</Explode>   </TermSet>   <TermSet>    <Term>"hemorrhagic"[All Fields]</Term>    <Field>All Fields</Field>    <Count>60599</Count>    <Explode>N</Explode>   </TermSet>   <TermSet>    <Term>"fever"[All Fields]</Term>    <Field>All Fields</Field>    <Count>164827</Count>    <Explode>N</Explode>   </TermSet>   <OP>AND</OP>   <TermSet>    <Term>"ebola"[All Fields]</Term>    <Field>All Fields</Field>    <Count>2698</Count>    <Explode>N</Explode>   </TermSet>   <OP>AND</OP>   <OP>GROUP</OP>   <OP>OR</OP>   <TermSet>    <Term>"ebola hemorrhagic fever"[All Fields]</Term>    <Field>All Fields</Field>    <Count>1076</Count>    <Explode>N</Explode>   </TermSet>   <OP>OR</OP>   <TermSet>    <Term>"ebola"[All Fields]</Term>    <Field>All Fields</Field>    <Count>2698</Count>    <Explode>N</Explode>   </TermSet>   <OP>OR</OP>   <TermSet>    <Term>"ebolavirus"[MeSH Terms]</Term>    <Field>MeSH Terms</Field>    <Count>1169</Count>    <Explode>Y</Explode>   </TermSet>   <OP>OR</OP>   <TermSet>    <Term>"ebolavirus"[All Fields]</Term>    <Field>All Fields</Field>    <Count>1259</Count>    <Explode>N</Explode>   </TermSet>   <OP>OR</OP>   <OP>GROUP</OP>  </TranslationStack><QueryTranslation>"hemorrhagic fever, ebola"[MeSH Terms] OR ("hemorrhagic"[All Fields] AND "fever"[All Fields] AND "ebola"[All Fields]) OR "ebola hemorrhagic fever"[All Fields] OR "ebola"[All Fields] OR "ebolavirus"[MeSH Terms] OR "ebolavirus"[All Fields]</QueryTranslation></eSearchResult>

hashie.rb

require 'open-uri'
require 'json'
require 'hashie'

response = open('http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola&retmode=json')
data = response.read
json = JSON.parse(data)

mash = Hashie::Mash.new(json)
mash.esearchresult.idlist # => => ["25587816", "25585832", "25585771", ...

jq_field.sh

$ cat users.json | jq '.users[].name'
"Alice"
"Bob"

jq_pubmed.sh

$ curl -s "http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola&retmode=json" \
  | jq '.esearchresult.idlist[]'

"25587816"
"25585832"
"25585771"
"25585757"
"25585723"
"25585496"
"25585384"
"25584879"
"25584356"

jq_select.sh

$ cat users.json | jq '.users[] | select(.age < 25)'
{
  "name": "Alice",
  "age": 24,
  "lang": "Ruby"
}

json.rb

require 'open-uri'
require 'json'

response = open('http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola&retmode=json')
data = response.read
json = JSON.parse(data)

puts json.class # => Hash
puts json.keys  # => header esearchresult
puts json['esearchresult']['count']  # => 2819
puts json['esearchresult']['idlist'] # => 25587816 25585832 25585771 ...

json.sh

$ curl -s "http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola&retmode=json" | head -n 20
{
    "header": {
        "type": "esearch",
        "version": "0.3"
    },
    "esearchresult": {
        "count": "2819",
        "retmax": "20",
        "retstart": "0",
        "idlist": [
            "25587816",
            "25585832",
            "25585771",
            "25585757",
            "25585723",
            "25585496",
            "25585384",
            "25584879",
            "25584356",
            "25584153",

open.rb

require 'open-uri'

response = open('http://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=pubmed&term=ebola&retmode=json')
# response.class #=> StringIO
# response.read.class #=> String

puts response.read
#=> {
#       "header": {
#           "type": "esearch",
#           "version": "0.3"
#       },
#       "esearchresult": {
#           "count": "2819",
#           "retmax": "20",
#           "retstart": "0",
#           "idlist": [
#               "25587816",

users.json

{"users": [{"name": "Alice", "age": 24, "lang": "Ruby"}, {"name": "Bob", "age": 28, "lang": "Python"}]}