Linux / UNIX: Convert Hexadecimal to Decimal Number

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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:

4095

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

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

Sample output:

A

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; [email protected]"|bc
}
d2h(){
  echo "obase=16; [email protected]"|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:

4095

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

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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26 comment

  1. 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.

  2. 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 !

  3. 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.

  4. 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.

  5. 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 $((0x100))

  6. 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

  7. 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

  8. 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).

  9. 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

  10. to JA & drpyro:
    yes, interesting, seems like once you set “ibase=2”, it treats the number in the subsequent “obase=10” in binary and interprets it as a decimal “2” and accordingly instructs to output in binary form, therefore producing the initial binary input number.
    But you needn’t fuss over converting the decimal “10” to binary “1010” just to let bc interpret obase correctly – just specify the “obase=10” before specifying the ibase:

    echo “obase=10; ibase=2; 111101101” | bc

    also, specifying “obase=10” after the binary input number works:

    echo “ibase=2; 111101101 ; obase=10;” | bc

    outputing in the decimal base is the default bc behaviour so can be dropped:

    echo “ibase=2; 111101101” | bc

  11. Your perl-example is a “,” after the format-part missing:
    # perl -e ‘printf “%b\n”, 10′
    1010
    # perl -e ‘printf “%d\n”, 0b1010′
    10

  12. #!/bin/bash
    #hextodec
    #convert any number of hex numbers to decimal
    #use "silent" as an argument to get briefer output for subsequent arguments. Example
    #hextodec abc silent fff
    if [[ ! $1 ]]
     then
      echo convert any number of hex numbers to decimal
      echo use \"silent\" as an argument to get briefer output for subsequent arguments. Example
      echo $0 abc silent fff
    fi
    for hex in $*
     do
      if [[ "$hex" == silent ]]
       then
        silent=1
        continue
       else
        if [[ "${hex/[^0-9A-Fa-f]}" != "$hex" ]]
         then
          echo "\"$hex\" is not a hex number - just use hex digits"
          continue
        fi
      fi
      let value=0x$hex
      if (( ! silent ))
       then
        echo -n "hex 0x$hex = decimal "
      fi
      echo $((value))
    done
    

    ————————————————————————–

    #!/bin/bash
    #convert any number of binary numbers to hex
    #use "silent" as an argument to get briefer output for subsequent arguments. Example
    #bintohex 11111 silent 111111
    if [[ ! $1 ]]
     then
      echo convert any number of binary numbers to hex
      echo use \"silent\" as an argument to get briefer output for subsequent arguments. Example
      echo $0 11111 silent 111111
    fi
    for binary in $*
     do
      if [[ "$binary" == silent ]]
       then
        silent=1
        continue
       else
        if [[ "${binary/[^01]}" != "$binary" ]]
         then
          echo "\"$binary\" is not a binary number - just use 0's and 1's"
          continue
        fi
      fi
      let value=2#$binary
      if (( ! silent ))
       then
        echo -n "binary 2#$binary = hexadecimal 0x"
      fi
      printf "%X\n" $value
    done
    
  13. A major problem with the people suggesting printf is the lack of precision compared to bc. Consider the following

    $ printf "%d\n"  0xD9416E53C29E8257A374A02F2862052032DDA5AE7ECCEAFF3553491E5D1DA02068A7888DF6ED573A73B7156ACEDF1A8A5339CC267D731C9B09D6FDBF422F9FAC05B564568B7CAAF613D7D6161BAEFC50F228CA81D862BDCF0D17833DF87C5B9869AFDD9A2E757BB14FD58EC62D4BE64AB98C8440318EE624700E10D645DFBC3B
    bash: printf: warning: 0xD9416E53C29E8257A374A02F2862052032DDA5AE7ECCEAFF3553491E5D1DA02068A7888DF6ED573A73B7156ACEDF1A8A5339CC267D731C9B09D6FDBF422F9FAC05B564568B7CAAF613D7D6161BAEFC50F228CA81D862BDCF0D17833DF87C5B9869AFDD9A2E757BB14FD58EC62D4BE64AB98C8440318EE624700E10D645DFBC3B: Numerical result out of range
    9223372036854775807
    

    vs

    $ echo "ibase=16; D9416E53C29E8257A374A02F2862052032DDA5AE7ECCEAFF3553491E5D1DA02068A7888DF6ED573A73B7156ACEDF1A8A5339CC267D731C9B09D6FDBF422F9FAC05B564568B7CAAF613D7D6161BAEFC50F228CA81D862BDCF0D17833DF87C5B9869AFDD9A2E757BB14FD58EC62D4BE64AB98C8440318EE624700E10D645DFBC3B" | bc
    
    15256206333236909607074123047335714924824051962962261484438970616724\
    16065731202741278668636933358898393872253458882879611872300713906719\
    21426741919669350334837200474802435375507601309711393907894616987077\
    89788816453030088048266333363441906590295054112097178868191240854462\
    8193927787051199707221470516418165819
    

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