How to compare two version numbers in a shell script

Last updated on November 25, 2020 by Dan Nanni

When you are writing a shell script, there are cases where you need to compare two version numbers, and proceed differently depending on whether one version number is higher/lower than the other. For example, you want to check for the minimum version requirement (i.e., $version ≥ 1.3.0). Or you want to write a conditional statement where the condition is defined by a specific range of version numbers (e.g., 1.0.0 ≤ $version ≤ 2.3.1).

If you want to compare two strings in version format (i.e., "X.Y.Z") in a shell script, one easy way is to use sort command. With -V option, the sort command can sort version numbers within text (in an increasing order by default). With -rV option, it can sort version numbers in a decreasing order.

Now let's see how we can use the sort command to compare version numbers in a shell script.

For version number string comparison, the following function definitions come in handy. Note that these functions use the sort command.

function version_gt() { test "$(echo "[email protected]" | tr " " "n" | sort -V | head -n 1)" != "$1"; }
function version_le() { test "$(echo "[email protected]" | tr " " "n" | sort -V | head -n 1)" == "$1"; }
function version_lt() { test "$(echo "[email protected]" | tr " " "n" | sort -rV | head -n 1)" != "$1"; }
function version_ge() { test "$(echo "[email protected]" | tr " " "n" | sort -rV | head -n 1)" == "$1"; }

These functions perform, respectively, "greater-than", "less than or equal to", "less than", and "greater than or equal to" operations against two specified version numbers. You will need to use bash shell due to function definitions.

Below is an example bash script that compares two version numbers.

#!/bin/bash

VERSION=$1
VERSION2=$2

function version_gt() { test "$(echo "[email protected]" | tr " " "n" | sort -V | head -n 1)" != "$1"; }
function version_le() { test "$(echo "[email protected]" | tr " " "n" | sort -V | head -n 1)" == "$1"; }
function version_lt() { test "$(echo "[email protected]" | tr " " "n" | sort -rV | head -n 1)" != "$1"; }
function version_ge() { test "$(echo "[email protected]" | tr " " "n" | sort -rV | head -n 1)" == "$1"; }

if version_gt $VERSION $VERSION2; then
   echo "$VERSION is greater than $VERSION2"
fi

if version_le $VERSION $VERSION2; then
   echo "$VERSION is less than or equal to $VERSION2"
fi

if version_lt $VERSION $VERSION2; then
   echo "$VERSION is less than $VERSION2"
fi

if version_ge $VERSION $VERSION2; then
   echo "$VERSION is greater than or equal to $VERSION2"
fi

If you find this tutorial helpful, I recommend you check out the series of bash shell scripting tutorials provided by Xmodulo.

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