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Need a fast oneline decimal-to-binary conversion without loop in bash.
Posted: Tue Apr 12, 2022 5:16 pm
by blumenwesen
Does anyone know a faster calculation path for decimal to binary than in a loop?
I think the principle is similar like from decimal to octal, only the calculation without a loop would be longer.
Code: Select all
#dec-bin ???
z="338"
echo -e $["$z"/32]$[$["$z"/2]%2]$["$z"%2] # failed attempt
#dec-bin
z="338"
y=""
while [ $z -ne 0 ]; do
y=$[$z%2]$y
z=$[$z/2]
done
echo $y
#dec-oct
z="338"
echo -e $["$z"/64]$[$["$z"/8]%8]$["$z"%8]
#dec-oct
z="338"
y=""
while [ $z -ne 0 ]; do
y=$[$z%8]$y
z=$[$z/8]
done
echo $y
Re: Need a fast oneline decimal-to-binary conversion without loop in bash.
Posted: Tue Apr 12, 2022 7:56 pm
by williams2
bash is really not good for arithmetic, usually something like bc is used. For example,
Code: Select all
# echo 'obase=2;338' | bc
101010010
#
## https://github.com/louisrubet/rpn
# rpn 338 bin
0b101010010
#
# ff 338 2 base ! . ;
\ Loading'ff.ff: help normal .now {{{ +longconds f. sqrt uart! hid'm
\ FreeForth 1.2 <http://christophe.lavarenne.free.fr/ff> Try: help
0; 101010010
#
# python -c 'print("{:b}".format(338))'
101010010
#
Do you really need it coded in bash?
Re: Need a fast oneline decimal-to-binary conversion without loop in bash.
Posted: Wed Apr 13, 2022 4:50 am
by blumenwesen
Thanks but I didnt want to take python anymore because they even changed basic databases so that other programs and libraries have more direct access.
Since 2.7 is no longer improved, many libraries no longer work properly.
I thought there was a way to calculate only with echo, because I found out that it works everywhere, only with binary I don't have an example yet.
Code: Select all
#hex-oct
z="0152"
echo -e $[$[16#"$z"]/64]$[$[$[16#"$z"]/8]%8]$[$[16#"$z"]%8]
#oct-hex
z="522"
echo -e $[$[8#"$z"]/256]$[$[$[8#"$z"]/16]%16]$[$[8#"$z"]%16]
#dec-hex
z="338"
echo -e $["$z"/256]$[$["$z"/16]%16]$["$z"%16]
#bin-hex
z="101010010"
echo -e $[$[2#"$z"]/256]$[$[$[2#"$z"]/16]%16]$[$[2#"$z"]%16]
# and so on ...
Re: Need a fast oneline decimal-to-binary conversion without loop in bash.
Posted: Wed Apr 13, 2022 5:29 am
by blumenwesen
I found the correct calculation only a little more cumbersome than thought and the hex conversion is incorrect.
Code: Select all
# z="255"
z="338"
z=$(echo -e $["$z"/256]$[$["$z"/16]%16]$["$z"%16])
# z=$(echo -e $["$z"/256]$[$["$z"/16]%16]$["$z"%16] | awk '{gsub("10", "a"); gsub("11", "b"); gsub("12", "c"); gsub("13", "d"); gsub("14", "e"); gsub("15", "f")}1')
echo -e $[($[16#$z]>>10)%2]$[($[16#$z]>>9)%2]$[($[16#$z]>>8)%2]$[($[16#$z]>>7)%2]$[($[16#$z]>>6)%2]$[($[16#$z]>>5)%2]$[($[16#$z]>>4)%2]$[($[16#$z]>>3)%2]$[($[16#$z]>>2)%2]$[($[16#$z]>>1)%2]$[($[16#$z]>>0)%2]