Cfrgtkky

I've seen some strange things.
I tried to convert hex to dec with bash Shell

I used very very simple command.

$ g_receiverBeforeToken=1158e460913d00000

$ echo $((16#$g_receiverBeforeToken))

1553255926290448384

As you guys know, this result should be '20000000000000000000'.

When I put in any other hex number, it was correct. But only 1553255926290448384 was weird.

It's not just that number, it's any number over 7fffffffffffffff, because it's using 64-bit integers and that's the largest one. 16-digit numbers over that wrap around and become negative (because of two's complement representation of signed integers):

$ echo $((16#7fffffffffffffff))

9223372036854775807

$ echo $((16#7fffffffffffffff + 1))

-9223372036854775808

$ echo $((16#8000000000000000))

-9223372036854775808

Past ffffffffffffffff (aka -1), it wraps back to zero:

$ echo $((16#ffffffffffffffff))

-1

$ echo $((16#ffffffffffffffff + 1))

0

$ echo $((16#10000000000000000))

0

Net result: only the last 16 hex digits actually matter; anything past that gets dropped off the high end of the 64-bit integer representation:

$ echo $((16#0000000000000010))

16

$ echo $((16#10000000000000010))

16

$ echo $((16#ffffffff0000000000000010))

16

Since 1553255926290448384 is 17 digits long, the first digit is being dropped off in this way:

$ echo $((16#1158e460913d00000))

1553255926290448384

$ echo $((16#158e460913d00000))

1553255926290448384

$ echo $((16#121345158e460913d00000))

1553255926290448384

You can do what you are looking to do using bc as a base conversion with a short script:

#!/bin/bash



## validate sufficient input

test -n "$1" || {

    printf "n error: insufficient input. usage:  %s num [obase (2)] [ibase (10)]nn" "${0//*//}"

    exit 1

}



## test for help

test "$1" = "-h" || test "$1" = "--help" && {

    printf "n  usage:  %s num [obase (2)] [ibase (10)] -- to convert numbernn" "${0//*//}"

    exit 0

}



## validate numeric value given for conversion (bash only test)

ival="${1^^}"

[[ $ival =~ [^0-9A-F] ]] && {

    printf "n error: invalid input. Input must be within upper/lower case hex character set [0-9A-Fa-f]nn"

    exit 1

}



ob=${2:-2}

ib=${3:-10}



# set obase first before ibase -- or weird things happen.

printf "obase=%d; ibase=%d; %sn" $ob $ib $ival | bc

Example Use/Output

$ bash hex2dec.sh -h



  usage:  hex2dec.sh num [obase (2)] [ibase (10)] -- to convert number

Using your example:

$ bash hex2dec.sh 1158e460913d00000 10 16

20000000000000000000

Also handy if you want it in binary as well:

$ bash hex2dec.sh 1158e460913d00000 2 16

10001010110001110010001100000100100010011110100000000000000000000