Reduce the amount of decimals positions using bash printf without rounding

Question

I am using printf to restrict the amount of decimal places of a number to 3 decimal places

printf "%.3f\n" 8.577772
8.578

I want to truncate this number to 3 decimal places WITHOUT rounding up so that it prints as 8.577.

Solutions with printf are preferred.

Answer 1

Assuming this is a variable, which can have any number of places before the decimal:

$ var=8.577772
$ printf "%s.%.3s\n" $( echo $var | tr '.' ' ' )
8.577

$ var=134.56789
$ printf "%s.%.3s\n" $( echo $var | tr '.' ' ' )
134.567