Bash script: specify bc output number format

Question

Greetings!

I uses bс to make some calculations in my script. For example:

bc
scale=6
1/2
.500000

For further usage in my script I need "0.500000" insted of ".500000".

Could you help me please to configure bc output number format for my case?

Answer 1

Can you put the bc usage into a little better context? What are you using the results of bc for?

Given the following in a file called some_math.bc

scale=6
output=1/2
print output

on the command line I can do the following to add a zero:

$ bc -q some_math.bc | awk '{printf "%08s\n", $0}'
0.500000

If I only needed the output string to have a zero for formatting purposes, I'd use awk.

Answer 2

Thank you!

Actually in my script I use function taken from here:

float_scale=6

function float_eval()
{
    local stat=0
    local result=0.0
    if [[ $# -gt 0 ]]; then
        result=$(echo "scale=$float_scale; $*" | bc -q 2>/dev/null)
        stat=$?
        if [[ $stat -eq 0  &&  -z "$result" ]]; then stat=1; fi
    fi
    echo $result
    return $stat
}

Answer 3

I believe here is modified version of the function:

float_scale=6

function float_eval()
{
    local stat=0
    local result=0.0
    if [[ $# -gt 0 ]]; then
        result=$(echo "scale=$float_scale; $*" | bc -q | awk '{printf "%f\n", $0}' 2>/dev/null)
        stat=$?
        if [[ $stat -eq 0  &&  -z "$result" ]]; then stat=1; fi
    fi
    echo $result
    return $stat
}

Answer 4

Just do all your calculations and output in awk:

float_scale=6
result=$(awk -v scale=$floatscale 'BEGIN { printf "%.*f\n", scale, 1/2 }')