jq json parser hash the field value - parsing

Question

I have a JSON file as the below:
[{
"macAddress": "ac:5f:3e:87:d7:1a",
"ip": "1.2.3.4"
},
{
"macAddress": "ac:5f:3e:87:d7:2a",
"ip": "1.2.3.4"
},
{
"macAddress": "ac:5f:3e:87:d7:3a",
"ip": "1.2.3.4"
}]
use jq to hash the macAddress field like so:
jq .[] | hash(.macAddress)
Can I define my own hash function and let jq to run the hash during the parsing process?
My expected hash function can be simple as using native linux command md5sum
echo -n "my_salt""42:12:20:2e:2b:ca" | md5sum
d973ea7c353e78ba1724efbc8054dfdc -
So the output json will be
[{
"macAddress": "d973ea7c353e78ba1724efbc8054dfdc",
"ip": "1.2.3.4"
},
{
"macAddress": "d973ea7c353e78ba1724efbc8054d2er",
"ip": "1.2.3.4"
},
{
"macAddress": "d973ea7c353e78ba2324efbc8054d123",
"ip": "1.2.3.4"
}]

Answer 1

My expected hash function can be simple as using native linux command md5sum
This stays native and might be suitable;
Invocation :
jq -c .[] "$jsonfile" |
while read -r jsonline ; do
hashmac="$(jq --arg mysalt "$mysalt" -s -j '
.[] | "\($mysalt)" + .macAddress' <<<"$jsonline" |
md5sum | cut -d ' ' -f1)"
jq --arg hashmac "$hashmac" -s -r '
.[] | .macAddress |= "\($hashmac)"' <<<"$jsonline"
done
Example file - /tmp/testfile:
[{
"macAddress": "ac:5f:3e:87:d7:1a",
"ip": "1.2.3.4"
},
{
"macAddress": "ac:5f:3e:87:d7:2a",
"ip": "1.2.3.4"
},
{
"macAddress": "ac:5f:3e:87:d7:3a",
"ip": "1.2.3.4"
},
{
"macAddress": "42:12:20:2e:2b:ca",
"ip": "1.2.3.4"
}]
Result Output:
{
"macAddress": "1f960fe4d24684ca44e5e67b6259362c",
"ip": "1.2.3.4"
}
{
"macAddress": "3527422754ecbfdd01d48b17fce87842",
"ip": "1.2.3.4"
}
{
"macAddress": "9bc8da72324448c3032a20fb67a31466",
"ip": "1.2.3.4"
}
{
"macAddress": "d973ea7c353e78ba1724efbc8054dfdc",
"ip": "1.2.3.4"
}
Comments:
-j causes jq to not output a newline, equivalent to your echo -n example
Variables in this example are sent to jq as strings using -arg, and referenced as "\($var)" as opposed to escaping the variable directly, for example:
"\($mysalt)" + .macAddress' (jq variable)
Instead of:
"'"$mysalt"'" + .macAddress' (direct shell substitution)
This example uses cut -d ' ' -f1 to trim off the -, but there's probably a better way
Alternate:
jq --arg hashmac "$hashmac" -s -r '.[] |= . + {"hashAddress":"\($hashmac)"}'
Would append the json
[
{
"macAddress": "ac:5f:3e:87:d7:1a",
"ip": "1.2.3.4",
"hashAddress": "1f960fe4d24684ca44e5e67b6259362c"
}
]
etc.

Answer 2

The accepted answer entails 2n + 1 invocations of jq, where n is the number invocations of the message digest function.
To reduce the number of invocations to just 2, see shell-out value to md5 (crypto) function