BASH comparing Linux version to number?

Question

I'm trying to work out how to compare the current openSuSE version number to a preset value.

I've got the current version of the installed OS in $VERSION_ID

I'm now trying to work out how to compare that to '42.3'. So if the value isn't greater than or equal to quit.

if [ ! "$VERSION_ID" -ge 42.3 ]; then
    echo "Sorry Bye";
fi

I'm getting: [: 42.3: integer expression expected But I don't know how to fix that

Any advise please Thanks

In general, version numbers aren't floating-point values; they are `.`-delimited sequences of integers. For instance, `42.10` is almost certainly a newer version than `42.9`. — chepner, Aug 31 '18 at 13:23
@chepner Good point, that dupe would solve the Y part of the XY problem ;) — Benjamin W., Aug 31 '18 at 13:53

Michael · Answer 1 · 2018-08-31T13:21:15.740

1

You can use a calculator bc:

if [ $(echo "$VERSION_ID<=42.3" |bc -l) -eq "1" ]; then 
    echo "Sorry Bye";
fi

edited Aug 31 '18 at 13:21

answered Aug 31 '18 at 13:18

Michael

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@Michael O. Thanks this seens to do what I need :) – Tom Aug 31 '18 at 13:30
Slight change so 42.3 and above is allowed: `if [ `echo $VERSION_ID'<'42.3 | bc -l` != 0 ]; then ` – Tom Aug 31 '18 at 13:32

chepner · Accepted Answer · 2018-08-31T13:58:56.400

0

Version numbers aren't floating point values; they are .-delimited sequences of integers. 42.27 is newer than 42.3, and 42.2.9 could be a valid version number.

Split the version number into its integer components, and compare them "lexiconumerically":

target=(42 3)
IFS=. read -a v_id <<< "$VERSION_ID"

for ((i=0; i <${#v_id[@]}; i++)); do
  if (( ${v_id[i]} == ${target[i]} )); then
    continue
  fi

  if (( ${v_id[i]} < ${target[i]} )); then
    echo "version < target"
  elif (( ${v_id[i]} > ${target[i]} )); then
    echo "version > target"
  fi
  break
done

edited Aug 31 '18 at 13:58

answered Aug 31 '18 at 13:29

chepner

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You can use `v_id[i]` and `target[i]` for arrays in arithmetic context, by the way. – Benjamin W. Aug 31 '18 at 13:58
I usually prefer `${...}` in arithmetic expressions, as a guard against undefined variables (the variable alone will default to 0, but the empty string from an expansion produces a syntax error). – chepner Aug 31 '18 at 13:59
Good point, too. – Benjamin W. Aug 31 '18 at 14:00

BASH comparing Linux version to number?

2 Answers2