Binary to hexadecimal and decimal in a shell script

Question

I have a context where I need to convert binary to hexadecimal and decimal and viceversa in a shell script. Can someone suggest me a tool for this?

Solution 1

It's fairly straightforward to do the conversion from binary in pure bash (echo and printf are builtins):

Binary to decimal

$ echo "$((2#101010101))"
341

Binary to hexadecimal

$ printf '%x\n' "$((2#101010101))"
155

Going back to binary using bash alone is somewhat more complex, so I suggest you see the other answers for solutions to that.

Solution 2

Assuming that by binary, you mean binary data as in data with any possible byte value including 0, and not base-2 numbers:

To convert from binary, od (standard), xxd (comes with vim) or perl's unpack come to mind.

od -An -vtu1 # for decimal
od -An -vtx1 # for hexadecimal

xxd -p # for hexa

perl -pe 'BEGIN{$\="\n";$/=\30};$_=unpack("H*",$_)' # like xxd -p

# for decimal:
perl -ne 'BEGIN{$\="\n";$/=\30;$,=" "}; print unpack("C*",$_)'

Now, to convert back to binary, awk (standard), xxd -r or perl's pack:

From the decimal output from od -tu1 or perl above:

LC_ALL=C awk '{for (i = 1; i <= NF; i++) printf "%c", $i}'
perl -ape '$_=pack("C*",@F)'

From the hexa perl or xxd -p above:

xxd -r -p
perl -pe 'chomp;$_=pack("H*",$_)'

Solution 3

You can use bc for this by manipulating the ibase and obase parameters:

The trick is that you need to be explicit about the bases. So if your ibase is 2, then if you set your obase to 10, it won't do anything, as 10 in binary is 2. Hence you need to use hexadecimal notation.

So binary to decimal would be (watch that obase is A)

Binary to decimal:

$> echo 'ibase=2;obase=A;11110001011010'|bc
15450

Binary to hex:

$> echo 'ibase=2;obase=10000;11110001011010'|bc
3C5A

If the 'output base' obase is changed first, it should be easier:

$> echo 'obase=10;ibase=2;11110001011010'|bc
15450
$> echo 'obase=16;ibase=2;11110001011010'|bc
3C5A

Solution 4

If you mean converting numbers from base-2 to 10 or 16 and back, bc is the standard tool to do that as already mentioned by psarossy.

decimal=123
binary=$(echo "obase=2;$decimal" | bc)
hex=$(echo "obase=16;ibase=2;$binary" | bc)

Some shells like zsh have builtin support for base conversion as part of their arithmetic expansion operators:

decimal=123
binary=$(([##2]decimal))
hex=$(([##16]decimal))
hex=$(([##16]2#$binary))
decimal=$((2#$binary))

and so on.

Both ksh93 and zsh also support:

typeset -i2 binary=123
typeset -i16 dec2hex=123 bin2hex='2#1111'

But note that, when expanded, $binary will have a 2# or 16# prefix (which you can strip with ${binary#*#}.

ksh93 also supports:

printf "%..2d\n" 123

to convert to binary.

Solution 5

As mentioned in previous answer you can do Binary to Decimal and Hexa Decimal as follows in Bash using echo and printf. I am just adding here how to convert from Decimal and Hex to binary using pure Bash.

Binary to Decimal using echo

echo "$((2#101010101))"
341

Binary to Hexa-Decimal using printf

printf '%x\n' "$((2#101010101))"
155

Integer decimal to Binary conversion using only Bash

Using only Bash, if you would like to convert decimal to binary, you can do it like the following:

touch dec2bin && chmod +x "$_" && vim "$_"

And then copy and paste the following:

#!/bin/bash
## converting decimal integer to binary, pass int as a parameter
num=$1;
dec2bin()
{   [ "$num" == "" ] && { printf "Error: Pass an integer\n"; exit 1; };
    op=2; ## Since we're converting to binary
    quo=$(( $num / $op)); rem=$(( $num % $op)); ## quotient and remainder
    remarray=(); ## array for putting remainder inside array
    remarray+=("$rem"); ## array expansion
        until [[ $quo -eq 0 ]]; do
            num=$quo; quo=$(( $num / $op)); ## looping to get all remainder untill 0
            rem=$(( $num % $op)); remarray+="$rem"; ## array expansion
        done
    binary=$(echo "${remarray[@]}" | rev); ## reversing array
    printf "$binary\n"; ## printing reversed array
}
main()
{   [[ -n ${num//[0-9]/} ]] &&
        { printf "Error: $num is not an integer bruv!\n"; return 1;
        } || { dec2bin $num; }
}
main;

And then try it from where you saved:

./dec2bin 420
110100100

Integer must be added!!

./dec2bin 420.py
420.py is not an integer bruv!

Hexadecimal to Binary conversion using only Bash

Similarly, hexadecimal to binary, as follows using only bash:

#!/usr/local/bin/bash
## converting hexadecimal to binary, pass hex as a parameter
hex=$1;
hex2bin()
{   [ "$hex" == "" ] && { printf "Error: Pass a hex\n"; exit 1; };
    op=2; num=$((16#$hex)); ## converting hex to integer
    quo=$(( $num/ $op)); rem=$(( $num% $op)); ## quotient and remainder
    remarray=(); remarray+=("$rem"); ## array expansion
        until [[ $quo -eq 0 ]]; do
            num=$quo; quo=$(( $num / $op)); ## looping to get all remainder untill 0
            rem=$(( $num % $op)); remarray+="$rem"; ## array expansion
        done
    binary=$(echo "${remarray[@]}" | rev); ## reversing array
    printf "$binary\n"; ## printing reversed array
}
main()
{
[[ -n ${hex//[0-9,A-F,a-f]/} ]] &&
    { printf "Error: $hex is not a hex bruv!\n"; return 1;
    } || { hex2bin $hex; }
}
main;

For example:

./hex2bin 1aF
110101111

Hex must be passed:

./hex2bin.bash XyZ
XyZ is not a hexa decimal number bruv!

View more solutions

Comments

[goldilocks]

This second example is wrong -- 'F' would be base 15, not 16 (decimal 16 in hex is 10, not F). Try echo 'ibase=2;obase=F;1111 which should equal decimal 15, ie. F in hex. It comes out as 10, which it is in base 15 (digits 0-E). It is also easier if you state the obase first, eg: echo 'obase=16;ibase=2;1111'|bc. No confusion.

[Bangi]

how about decimal to hexadecimal.

[Andrea Corbellini]

What's the point of using printf %d for bin2dec? $(( ... )) already gives a decimal result, echo is enough.

[clerksx]

@AndreaCorbellini - Personal preference. In general, I use printf '%s\n' foo instead of echo for a variety of reasons (mostly portability), for the same reason, I don't use it here.

[Andrea Corbellini]

@ChrisDown: I though this question was explicitly about Bash (which has a well-implemented echo builtin). My bad!

[manatwork]

Now it is worst. Once you set ibase, you have to provide input in that base, even for obase. So in your example would be echo 'ibase=2;obase=10000;11110001011010'|bc. Better listen to goldilocks's advice and reverse the order – first set obase, then ibase.

[Franki]

I don't know of any shorter way for bash and ash shells to convert numbers back into binary than to use bc : printf -- 'obase=2;%d\n' "341" | bc , however, I don't find it fast enough

[Zimba]

xxd -r gives binary data, not ascii equivalent of hex data. ie 11111111 in binary file is FF in hex data. The question is asking to give 11111111 in ascii (displayable on screen)