In jq, how to get tonumber to output decimal instead of scientific notation

Unfortunately there is currently no way in jq to modify the representation of JSON numbers as such; the best one can do is modify their representation as strings. Here is a simple illustration of what can be done.

to_decimal takes as input a JSON number (or a valid JSON string representation of a number, possibly with a leading "+") as input, and converts it into a suitable string, e.g.:

["0","1","-1","123","-123",".00000123","1230000","-.00000123","-0.123","0.123","0.001"]

produces:

[0,"0"]["+1","1"][-1,"-1"][123,"123"][-123,"-123"][1.23e-06,".00000123"][1230000,"1230000"][-1.23e-06,"-.00000123"][-0.123,"-0.123"][0.123,"0.123"][0.001,"0.001"]

Notice that any leading "+" is dropped.

to_decimal

def to_decimal:  def rpad(n): if (n > length) then . + ((n - length) * "0") else . end;  def lpad(n): if (n > length) then ((n - length) * "0") + . else . end;  tostring  | . as $s  | capture( "(?<sgn>[+-]?)(?<left>[0-9]*)(?<p>\\.?)(?<right>[0-9]*)(?<e>[Ee]?)(?<exp>[+-]?[0-9]+)" )  | if .e == "" then (if .sgn == "+" then $s[1:] else $s end)    else (.left|length) as $len    | (.exp|tonumber) as $exp    | (if .sgn == "-" then "-" else "" end ) as $sgn    | if $exp < 0 then "." + (.left | lpad(1 - $exp - $len)) + .right      else (.left | rpad($exp - $len)) + "." + .right      end      | $sgn + .    end ;