How to Convert Hex to Decimal in Bash [6+ Methods]

Decimal and hexadecimal are popular number systems. Decimal is base 10, using 10 symbols (0-9), while hexadecimal is base 16. Hexadecimal uses 16 symbols: 0-9 and A-F (or a-f), where A=10, B=11, C=12, D=13, E=14 and F=15. Bash users often convert hexadecimal numbers to decimal and vice-versa. Common techniques to convert hex to decimal in Bash are:

1. Using arithmetic expansion with base conversion:
   echo $((16#hex_number))
2. Using bc command:
   echo "ibase=16; hex_number" | bc
3. Using printf command:
   printf "%d" 0xhex_number
4. Using perl code:
   perl -le 'print hex("hex_number");'
5. Using Python Utilities in Bash:
   python3 -c 'print(int("hex_number", 16))'
6. Using dc command:
   dc -e '16i hex_number p'

Let’s explore the methods mentioned above for converting hexadecimal number to decimal, along with some additional approaches.

1. Using Arithmetic Expansion

Arithmetic expansion supports base conversion of numbers. The default base for Bash arithmetic is 10, but one can specify a different base using the syntax base#number. Regardless of the original base of a number, arithmetic expansion in Bash always returns the equivalent decimal value of the number. For instance, the following command gives the decimal equivalent of the hexadecimal number “FF” :

echo $((16#FF))

The image shows that the command returns 255 which is the decimal equivalent of hexadecimal “FF”.

To take a hexadecimal number from the user and find its equivalent decimal, follow this script below:

#!/bin/bash

# Input: Hexadecimal number
read -p "Enter the hexadecimal number: " hex_number
# Conversion using Bash arithmetic
decimal_number=$((16#${hex_number}))

# Output
echo "Equivalent Decimal: $decimal_number"

As you can see, in the first execution, the user provides A and the program returns 10. In the second execution, the program returns 255 as the decimal equivalent of hex “FF” is 255. In both runs, the program perfectly converts the given hex number to decimal.

2. Using “bc” Command With “ibase” and “obase”

To convert hexadecimal numbers to decimal using bc (Basic calculator) command, use ibase and obase to define the input base and output base respectively. The default base in bc is 10. So it isn’t mandatory to mention obase when you convert hex to decimal. Look at the example below:

echo "ibase=16; FF" | bc

Here, the input base is 16 and the given hex number is “FF”. The output base is not defined explicitly. However, if you want to specify the output base, you can use the code below:

echo "ibase=16;obase=A;1A" | bc

obase value A denotes that the output base is 10. So, the above command will convert hexdecimal “1A” to its equivalent decimal. The first command converts hex “FF” to its decimal which is 255. The second command successfully converts hex “1A” to its equivalent decimal which is 26. The output base is set to decimal(or A) in the second command, however, the first command uses default ouput base.

3. Using “printf” Command

The printf command and its format specifiers are enough for converting a hexadecimal number to decimal. The format specifier %d is used to print a decimal integer. To convert a hex number to decimal provide the hexadecimal literal after 0x just like the following commands:

printf "%d\n" 0xA
printf "%d\n" 0xff
printf "%d\n" 0xFF

0x indicates that the following characters are in hexadecimal format. For example, 0xA represents the hexadecimal number A. \n is a newline character, which adds a line break after printing the number.The first command converts a hexadecimal literal “A” to its decimal equivalent (10) using printf. The subsequent commands test the printf command with hexadecimal literals “ff” and “FF”, returning 255 as their decimal equivalents.

4. Using “perl” Command

One can execute Perl code in Bash using the perl command with -e option. In Perl, there is a function called hex that takes hexadecimal values and returns corresponding decimal numbers. Look at the simple command below:

perl -le 'print hex("F");'

As you can see, when “F” is provided in the hex function, it produces the decimal ouput 15.

5. Using Python Utilities

Once a Python version is installed in the Bash shell, users can execute Python code using the python2 or python3 command. The int function in Python takes two arguments, the first one represents the number and the second one is the base of the number used in the first argument. The default base is 10. The syntax is:

int(x, base=10)

To convert a hex number to decimal with above syntax, set base value 16 and replace x with the hex number. Following command returns the decimal equivalent of hexadecimal literal “FF”.

python -c 'print(int("FF", 16))'

The command is tested for finding the decimal of hex literal “F”, “FF” and “A”. Equivalent decimals of those hex literals are displayed in the image above.

6. Using “dc” Command

The dc (desk calculator) command can convert a hex number to decimal. The -e option of this command indicates that the string followed by the command name should be treated as an expression. To convert hex to decimal in Bash using dc, see the following command:

dc -e '16i F p'

The command returns 15 as the equivalent decimal of hexadecimal “F”.

7. Using Ruby Code

Ruby is a programming language. Bash users can easily run ruby code in a Bash shell. To convert a hex number to decimal you can use ruby command with its option -e like the following:

ruby -e 'p "FF".to_i(16)'

The image shows that when the hexadecimal literal “FF” is passed to the command, it returns 255 as the output.

8. Using Node.js

Javascript has a function called parseInt that can convert hex numbers to decimal. Fortunately, Bash users can run Javascript code in the shell. Here is a simple code that converts hexadecimal “FF” to its decimal value 255.

node -e "console.log(parseInt('FF', 16))"

9. Using Rhino

One can pass a heredoc to rhino and convert a hex number to decimal. Here’s how:

rhino <<EOF
print(parseInt('FF', 16))
EOF

As you can see, the rhino code converts the hexadecimal “FF” to the decimal equivalent 255.

10. Using User-Defined Function

Apart from the tools and commands, one can utilize full-fledged Bash programming to define a function for hex-to-decimal conversion. The following function is written from scratch to convert a hex number to decimal:

#!/bin/bash

declare -A hex_digit_val=(
[0]=0 [1]=1 [2]=2 [3]=3
[4]=4 [5]=5 [6]=6 [7]=7
[8]=8 [9]=9 [a]=10 [b]=11
[c]=12 [d]=13 [e]=14 [f]=15
)

hex_to_decimal() {
local hex=${1,,}  # Convert to lowercase to handle both upper and lower case hex
local base
local dec=0

for ((i = 0; i < ${#hex}; i++)); do
base=${hex:$i:1}
dec=$((dec * 16 + hex_digit_val[$base]))
done
echo $dec
}

# Example usage
result=$(hex_to_decimal "1A")
echo $result

Two hexadecimal number “FF” and “1A” are provided in two different executions of the script. The program returns 255 and 26 as the decimal of “FF” and “1A” respectively.

How to Convert A List of Hexadecimal Numbers to Decimal

Sometimes it’s necessary to convert multiple hex numbers or a list of hex numbers into decimals. To convert a list of hexadecimal numbers into decimals use a loop to iterate over each number of the list. Take the following list of hexadecimal numbers in hex_numbers.txt file as an example:

# hex_numbers.txt
D8E4
FF2B
1A
4C91A7
8D3F12B

I use a while loop to convert each hexadecimal number of the list into decimals. Check the following script to convert a list of hexadecimal numbers to decimal in Bash

#!/bin/bash

echo "Equivalent decimal numbers:"

# Read the file line by line
while IFS= read -r line; do
# Convert hexadecimal to decimal
decimal=$(echo "ibase=16; $line" | bc)
echo "$decimal"
echo

done < hex_numbers.txt

As you can see, the program converts all the hexadecimal numbers of the list into their decimal equivalent.

Conclusion

In conclusion, hex-to-decimal conversion in Bash is fairly easy. Users can work seamlessly with different numerical bases in the Bash shell. To do the task, you can adapt any technique discussed in this article. Hope you can choose the best way to convert your hex numbers to decimal.

People Also Ask

How to convert decimal numbers to hex in Bash?

To convert decimal numbers to hex in Bash, use the printf command with %x format specifier. For example:

echo $(printf "%x" 255)

Lowercase x returns lowercase hex literal whereas uppercase X returns uppercase hex literal. For example ouput of the above code will be ff. But if you use "%X" as format specifier the output will be FF.

What is the simpliest way to convert hex to decimal and vice-versa?

The simplest way to convert hexadecimal to decimal and vice versa in Bash is by defining a function using bc command. The following function can be useful for converting hexadecimal to decimal as well as decimal to hex:

#!/bin/bash

h2d(){
echo "ibase=16; $@" | bc
}
d2h(){
echo "obase=16; $@" | bc
}
# Convert the hex numbers to decimal
h2d "FF"
# Convert the decimal numbers to hex
d2h 10

Does hex number system use a decimal point?

No. The hexadecimal number system does not use a decimal point. The representation of values in hex is integer-based, and there is no explicit decimal point. If fractional values need to be represented, it’s typically done by using a whole number part and a separate part for fraction, rather than a decimal point within the hex number itself.

What is the limit of Bash hex to decimal conversion?

Bash hex to decimal conversion is limited to 64-bit integers, equivalent to 16 hexadecimal digits. The maximum representable hexadecimal value is 7fffffffffffffff. When a hex number exceeds 16 digits, Bash considers only the last 16 digits for conversion. For example:

echo $((16#1157e470953d0000))
echo $((16#11157e470953d0000))

The decimals of 1157e470953d0000 and 11157e470953d0000 are the same because the second hex number is 17 digits long, so Bash drops the first character. This makes both the hex number equal so the equivalent decimal.

How to convert hex to binary in Bash?

To convert hex to binary use the bc tool. For instance, following code converts the hexadecimal “FF” to its binary:

echo "obase=2; ibase=16; FF" | bc