Syntax

You need to use the following bc syntax to covert number:

# Convert octal to hexa ##
echo "obase=16; ibase=8; octal-number-here" | bc
 
## convert base 8 (octal) number 17 to hexadecimal ##
echo "obase=16; ibase=8; 17" | bc

Sample outputs:

F

Where,

• obase = Set output base (like 2, 8, 10, 16)
• ibase = Set input base (like 2, 8, 10, 16)
• 17 = Convert this number to ibase. The input must be given as per obase.

To convert hexadecimal to octal use the following syntax:

# Convert hexa to  octal ##
echo "obase=8; ibase=16; hex-number-here" | bc
 
## convert base 16 (hex) number 10 to octal ##
echo "obase=8; ibase=16; 100" | bc

Sample outputs:

400

The following will convert whole file of octal to hex, one per line:
( echo "obase=16; ibase=8" ; cat octal-data-file.txt ) | bc

printf command example

You can also use the printf command as follows:

## Convert hex # 0x100 to octal base ##
printf "%o\n" 0x100

Sample outputs:

400

Or

## Convert octal # 4242 to hex base ##
printf "%x\n" 04242

Sample output:

8a2

Please note that a hex base number must prefix with 0x and an octal base number must prefix with 0.