base conversion script for BASH
2023-11-04
I got tired of starting a calculator or wasting energy by doing an internet query to convert numerical bases so I wrote a script.
Update 2023-11-08: Emilis reached out and suggested to swap the order of the input parameters. This would make aliassing the script much easier. That's a great idea! Thanks Emilis! The script below is updated as per their suggestion.
Shell scripts are powerful. Each shell command — and there are many of them — does one thing and does it well. It is the combination of these building blocks that multiply their potential.
Anyway.
At times I need to do a lot of conversions between decimal, hexadecimal and binary numbers. Over time I've gotten somewhat okay of doing _some_ of them in my head or simply remembering them. But regardless I had to use a calculator or use a conversion website, which was tiring.
So eventually I got around to writing a short shell script.
#!/usr/bin/env bash
if [ $# -ne 2 ]; then
basename=$(basename $0)
echo "Converts a decimal number into another base"
echo "Usage: $basename target_base decimal_number"
echo
echo "Examples:"
echo " $basename 2 30 converts decimal 30 to binary 11110"
echo " $basename 16 73 converts decimal 73 to hexadecimal 4B"
exit 1
fi
decimalNum=$2
obase=$1
prefix=""
# convert bases
if [[ $obase == "h" || $obase == "hex" ]]; then obase=16
elif [[ $obase == "o" || $obase == "oct" ]]; then obase=8
elif [[ $obase == "b" || $obase == "bin" ]]; then obase=2
fi
# helpful prefixes
if [ $obase -eq 16 ]; then prefix="0x"
fi
targetNum=$(echo "obase=$obase;$decimalNum" | bc)
echo "$decimalNum in base $obase is $prefix$targetNum"As is usually the case, the actual logic of the script is quite short — in this case: a single line — and the majority is taken up by input sanitation, usage hints and convenience conversion.
`bc` is actually a complete calculator, capable of so much more. But I'm scripting it by setting it to an output conversion base and then simply passing a decimal number.
aliases
Let's say you need conversion to hexadecimal more than anything else. With the updated parameter order you can make an alias like `alias to-hex='bases.sh 16'` and use it conveniently as `# to-hex 73`. Nice. Thanks again Emilis!
Links
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Source