Question

What might be the most concise way in bash to convert a number into a bitfield character string like 1101?

In effect I am trying to do the opposite of

echo $[2#1101]

Why: I need to send a parameter to a program that takes bitfields in the form of a full string like “0011010110” but often only need to enable one or few bits as in:

SUPPRESSbits=$[1<<16] runscript.sh  # OR
SUPPRESSbits=$[1<<3 + 1<<9] runscript.sh  # much more readable when I know what bits 3 and 9 toggle in the program

Then runscript.sh then sees in its env a SUPPRESSbits=65536 rather than SUPPRESSbits="1000000000000000" and ends in parse error.

Answer 1

The easy way:

$ dc <<<2o123p
1111011

$ bc <<<'obase=2; 123'
1111011