Bash shell Decimal to Binary base 2 conversion

Question

I\'m looking for an easy way in Bash to convert a decimal number into a binary number. I have variables that need to be converted:

$ip1 $ip2 $ip3 $ip4
         


        

Answer 1

Convert decimal to binary with bash builtin commands (range 0 to 255):

D2B=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})

echo ${D2B[7]}

00000111

echo ${D2B[85]}

01010101

echo ${D2B[127]}

01111111

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To remove leading zeros, e.g. from ${D2B[7]}:

echo $((10#${D2B[7]}))

111

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This creates an array with 00000000 00000001 00000010 ... 11111101 11111110 11111111 with bash‘s brace expansion. The position in array D2B represents its decimal value.

See also: Understanding code ({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1})