Linux / UNIX: Convert Hexadecimal to Decimal Number

by Vivek Gite on February 6, 2009 · 16 comments

How do I convert hex number to decimal number using a shell script under UNIX / Linux operating systems?

Hexadecimal (hex) is a numeral system with a radix, or base, of 16. It uses sixteen distinct symbols, most often the symbols 0–9 to represent values zero to nine, and A, B, C, D, E, F (or a through f) to represent values ten to fifteen.

bc - An arbitrary precision calculator language

There is no need to write a shell script. You can simply use the following syntax at the shell prompt to convert hex to decimal number or vice versa.

bc: Hexadecimal or Binary Conversion

To convert to decimal, set ibase to 16, enter:

echo "ibase=16; hex-number"|bc
echo "ibase=16; FFF"|bc

Sample output:

To convert to hexadecimal, set obase to 16, enter:

echo "obase=16; decimal-number"|bc
echo "obase=16; 10"|bc

Sample output:

ibase and obase define the conversion base for input and output numbers under bc. The default for both input and output is base 10. Add following function to your ~/.bashrc:

h2d(){
  echo "ibase=16; $@"|bc
}
d2h(){
  echo "obase=16; $@"|bc
}

The above two functions can be used from the command line as follows:
$ h2d 100 $ d2h AC

Base conversion using printf shell builtin

You can also use printf a shell builtin as well as /usr/bin/printf. To convert decimal to hex, you'd type:

printf "%x\n" 4095

Sample outputs:

fff

To convert hex to decimal, you'd type:

printf "%d\n" 0xfff

Sample outputs:

You can save result to a shell variable and print it using printf or echo command:

output=$(printf "%d\n" 0xfff)
echo "${output}"
printf "%d\n" $output

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{ 16 comments… read them below or add one }

1 Amir Watad February 7, 2009: Hi.
A great post. Thank you for sharing.
BTW, a small correction, I think you swapped the function names h2d/d2h by mistake.
Will surely write about this in my blog. will give you the credits of course.
Thanks again.
Reply
2 Loïc Pefferkorn February 7, 2009: Hello,
Thank you for the tip.
wcalc is also a handy way to do such convertions, and I found it easier to use :
To convert from hex to decimal :
$ echo “0xff”|wcalc -d
= 255
To convert from decimal to hex:
echo “255″|wcalc -h
= 0xff
Binary and octal bases are also handled., and there is a _lot_ of others options !
Reply
3 sanjeev February 7, 2009: I tried this but i am not able to do this.
I edited “~/.bashrc ” file copy and pasted the above code.
Reply
4 Vivek Gite February 7, 2009: @Sanjeev,
You need to logout and login again so that functions get loaded.
@Loïc Pefferkorn
Thanks for sharing wcalc tool.
Reply
5 tim February 7, 2009: You can also source your .bashrc file:
. ~/.bashrc
Reply
6 Peck February 7, 2009: There’s an error on d2h. It’s ibase=16 to change input format to hex.
This gives the right value AC -> 172
Reply
7 Maqbool Patel February 8, 2009: Thanks, these days I am working on some byte level code reading file offsets and I was using a calculator to do this conversion. Never thought of this. Saved me lots of time. Especially the trick of adding to the .bashrc file, neat.
Reply
8 Mockey Chen February 9, 2009: How about just using printf, for example:
convert dec to hex:
$ printf “%x” 100
convert hex to dec:
$ printf “%d” 0xf4
simple and easy way.
Reply
9 asdf February 15, 2009: 0xac != 99, which one should see on a first glance or at least manually check before posting.
bc defaulting to decimal for input AND output saved you in your first example.
Finally clobbering and depending on the .bashrc when there is printf on every unix is unnecessary.
Reply
10 mhymn February 25, 2009: aptitude install gbase && man gbase
:)
Reply
11 PK March 16, 2009: I agrre with Mockey Chen.
convert dec to hex:
$ printf “%x” 100
convert hex to dec:
$ printf “%d” 0xf4
Or simply do in bash (for hex to dec. conversion):
echo $((0×100))
Reply
12 PK March 16, 2009: One more way I know.
from dec. to hex. conversion:
$echo ‘ibase=10; obase=16; 1237184449′ | bc
49BDEFC1
from hex. to dec. conversion: (here you specify obase in hex notation ( A=10 )
$echo ‘ibase=16; obase=A; 49BDEFC1′ | bc
1237184449
Reply
13 drpyro July 4, 2009: this command fail to give me the result on base 10, im i writing it the wrong way ?
echo "ibase=2;obase=10;111101101" | bc
when i omit obase i have the right answer exp: echo "ibase=2;111101101" | bc which is :493
I’m using bc 1.06.94
Reply
14 Justin Anonymous September 23, 2009: As others have mentioned, there is so much wrong with this article. Someone needs to update it.
drpyro: what is not mentioned is once you set ibase, all numbers after are treated in that base. For your code, it should look like this:
echo "ibase=2; obase=1010; 111101101" | bc
Get it? The obase number has to be in binary (1010b = 10 decimal).
Reply
15 adithya kiran February 23, 2011: Hi,
You can use the following command to convert from any to any base.. for example binary to dec and dec to binary
# perl -e ‘printf “%b\n” 10′
1010
# perl -e ‘printf “%d\n” 0b1010′
10
Reply
16 sovan November 25, 2011: how the conversion will possible when a user will give a number on his choice or from command line argument.
Reply