Comparing numbers in Bash

Question

I\'m starting to learn about writing scripts for the bash terminal, but I can\'t work out how to get the comparisons to work properly. The script I\'m using is:

Answer 1

I solved this by using a small function to convert version strings to plain integer values that can be compared:

function versionToInt() {
  local IFS=.
  parts=($1)
  let val=1000000*parts[0]+1000*parts[1]+parts[2]
  echo $val
}

This makes two important assumptions:

1. Input is a "normal SemVer string"
2. Each part is between 0-999

For example

versionToInt 12.34.56  # --> 12034056
versionToInt 1.2.3     # -->  1002003

Example testing whether npm command meets minimum requirement ...

NPM_ACTUAL=$(versionToInt $(npm --version))  # Capture npm version
NPM_REQUIRED=$(versionToInt 4.3.0)           # Desired version
if [ $NPM_ACTUAL \< $NPM_REQUIRED ]; then
  echo "Please update to npm@latest"
  exit 1
fi

Answer 2

There is also one nice thing some people might not know about:

echo $(( a < b ? a : b ))

This code will print the smallest number out of a and b