问题
I am trying to get some trade information from an exchange websocket. Both values .p and .q are enclosed between double quotes in the JSON I get from the socket.
When I try to multiply two values, it says I am trying to multiply two strings. So I pass those strings though the tonumber filter and the error message changes a bit, but can't get it to work really.
JSON:
{"e":"aggTrade","E":1562109562958,"s":"BTCUSDT","a":134343336,"p":"10796.60000000","q":"0.00139000","f":147532295,"l":147532295,"T":1562109562951,"m":false,"M":true}
The commands below are followed by their outputs:
... | jq '"\(.p*.q)"'
jq: error (at <stdin>:1): string ("10796.6000...) and string ("0.00139000") cannot be multiplied
Then:
... | jq '"\(.p|tonumber*.q|tonumber)"'
jq: error (at <stdin>:1): Cannot index string with string "q"
... | jq '"\("\(.p|tonumber)"*"\(.q|tonumber)")"'
jq: error (at <stdin>:1): string ("10796.6") and string ("0.00139") cannot be multiplied
The closest I get is with the code below, but it outputs many pages of results and I only expect one result...
... | jq '.q as $qtty | "\(.p|tonumber*$qtty|tonumber)"'
Or:
... | jq '.q as $qtty | "\(.p|tonumber*"\($qtty|tonumber)")"'
It outputs too many numbers!
Even with the -r option, it does not work. I would expect just the raw result of multiplication to appear, like so:
15.0072740
回答1:
Keep it simple,
jq -r '(.p | tonumber)*(.q | tonumber)'
来源：https://stackoverflow.com/questions/56861281/jq-how-to-multiply-values-that-are-recognised-as-strings