shell-out value to md5 (crypto) function

Question

I'm looking for a solution where I'm building out a JSON record and need to generate some text in JQ but pipe this text to an MD5 sum function and use it as a value for a key.

echo '{"first": "John", "last": "Big"}' | jq '. | { id: (.first + .last) | md5 }'

From looking at the manual and the GH issues I can't figure out how to do this since a function can't call out to a shell and there is not built in that provides a unique hash like functionality.

Edit

A better example what I'm looking for is this:

echo '{"first": "John", "last": "Big"}' | jq '. | {first, last, id: (.first + .last | md5) }'

to output:

{
  "first": "John",
  "last": "Big",
  "id": "cda5c2dd89a0ab28a598a6b22e5b88ce"
}

Edit2

and a little more context. I'm creating NDJson files for use with esbulk. I need to generate a unique key for each record. Initially, I thought piping out to the shell would be the simplest solution so I could either use sha1sum or some other hash function easily, but that is looking more challenging than I thought.

A better example what I'm looking for is this:

echo '[{"first": "John", "last": "Big"}, {"first": "Justin", "last": "Frozen"}]' | jq -c '.[] | {first, last, id: (.first + .last | md5) }'

to output:

{"first":"John","last":"Big","id":"cda5c2dd89a0ab28a598a6b22e5b88ce"}
{"first":"Justin","last":"Frozen","id":"af97f1bd8468e013c432208c32272668"}

Answer 1

Here is an efficient solution to the restated problem. There are altogether just two calls to jq, no matter the length of the array:

json='[{"first": "John", "last": "Big"}, {"first": "Justin", "last": "Frozen"}]'

echo "$json" |
jq -c '.[] | [.[]] | add' |
while read -r line ; do echo "$line" | md5 ; done |
jq -s -R --argjson json "$json" 'split("\n")
  | map(select(length>0))
  | . as $in
  | reduce range(0;length) as $i ($json; .[$i].id = $in[$i])'

This produces an array. Just tack on |.[] at the end to produce a stream of the elements.

Or a bit more tersely, with the goal of emitting one object per line without calling jq within the loop:

jq -c --slurpfile md5 <(jq -c '.[] | [.[]] | add' <<< "$json" |
    while read -r line ; do printf '"%s"' $(md5 <<< "$line" ) ; done) \
 '[., $md5] | transpose[] | .[0] + {id: .[1]}' <<< "$json"

Distinct Digest for each Record

I need to generate a unique key for each record.

It would therefore make sense to compute the digest based on each entire JSON object (or more generally, the entire JSON value), i.e. use jq -c ‘.[]’

Answer 2

jq + md5sum trick:

json_data='{"first": "John", "last": "Big"}'
jq -r '.first + .last| @sh' <<<"$json_data" | md5sum | cut -d' ' -f1 \
| jq -R --argjson data "$json_data" '$data + {id: .}'

Sample output:

{
  "first": "John",
  "last": "Big",
  "id": "f9e1e448a766870605b863e23d3fdbd8"
}

Answer 3

Using tee allows a pipeline to be used, e.g.:

echo '{"first": "John", "last": "Big"}' |
    tee >( jq -r '.first + .last' | md5 | jq -R '{id: .}') |
    jq -s add

Output:

{
  "first": "John",
  "last": "Big",
  "id": "cda5c2dd89a0ab28a598a6b22e5b88ce"
}

Edit2:

The following uses a while loop to iterate through the elements of the array, but it calls jq twice at each iteration. For a solution that does not call jq at all within the loop, see elsewhere on this page.

echo '[{"first": "John", "last": "Big"}, {"first": "Justin", "last": "Frozen"}]' |
jq -c .[] |
while read -r line ; do
    jq -r '[.[]]|add'  <<< "$line" | md5 |
        jq  --argjson line "$line" -R '$line + {id: .}'
done

Answer 4

Looking around a little farther I ended up finding this: jq json parser hash the field value which was helpful in getting to my answer of:

echo '[{"first": "John", "last": "Big"}, {"first": "Justin", "last": "Frozen"}]' > /tmp/testfile

jsonfile="/tmp/testfile"
jq -c .[] "$jsonfile" | while read -r jsonline ;
do
  # quickly parse the JSON line and build the pre-ID out to get md5sum'd and then store that in a variable
  id="$(jq -s -j -r '.[] | .first + .last' <<<"$jsonline" | md5sum | cut -d ' ' -f1)"
  # using the stored md5sum'd ID we can use that as an argument for adding it to the existing jsonline
  jq --arg id "$id" -s -c '.[] | .id = "\($id)"' <<<"$jsonline"
done

output

{"first":"John","last":"Big","id":"467ffeee8fea6aef01a6ffdcaf747782"}
{"first":"Justin","last":"Frozen","id":"fda76523d5259c0b586441dae7c2db85"}