Compare numerical output of command bash - linux

Question

I am running a script that bumps a parameter value in a file:
Before the script executes:
$cat file
revision 1.2 date: 2018/11/15 09:28:12; author: root; state: Exp;
lines: +1 -1
After running the script:
$cat file
revision 1.3 date: 2018/11/15 09:28:12; author: root; state: Exp;
lines: +1 -1 revision 1.2 date: 2018/11/15 09:28:12; author: root;
state: Exp; lines: +1 -1
I need a script that could checks if the version is updated/bumped as one version greater than the previous version, if yes it should echo the message as 'Script ran successfully'.
$grep -iw 'revision' file | head -1 | cut -d' ' -f2
1.2
$sh <script>
$grep -iw 'revision' file | head -1 | cut -d' ' -f2
1.3
$echo -e "Script ran successfully!!! \n"

Answer 1

Here's a function bumped that will compare to version strings and determine if they are in succession. I made a couple of assumptions in the comparison. The number of "decimal points" has to be the same. I also have left the door wide open for big errors , see my last test case. Consider this quick and dirty. It would probably be better to write logic to compare each decimal value and make sure that the last decimal place was one more than the previous. A more correct version would be able to compare a.b.c with d.e.f by first comparing a == d , then b == c , and then f == c + 1. However, depending on what you are trying to do, quick and dirty may be the easiest to maintain.
Without any additional discussion, here is the quick and dirty version:
function bumped() {
prev=$1
next=$2
PREV=$( sed 's/[^0-9]//g' <<<"$prev" )
NEXT=$( sed 's/[^0-9]//g' <<<"$next" )
[ $(( NEXT - PREV )) -eq 1 ]
}
function testcases() {
cat <<EOF
1.2 1.3 0
1.3 1.2 1
1.2.1 1.2.2 0
1.3 1.3.1 1
EOF
}
testcases | while
read prev next expected extra
do
bumped $prev $next
observed=$?
result="Success"
[ $observed -ne $expected ] && result="Failed"
echo "$result: bumped( $prev , $next ) = $observed ( expected: $expected )"
done
The above program yields these results:
Success: bumped( 1.2 , 1.3 ) = 0 ( expected: 0 )
Success: bumped( 1.3 , 1.2 ) = 1 ( expected: 1 )
Success: bumped( 1.2.1 , 1.2.2 ) = 0 ( expected: 0 )
Success: bumped( 1.3 , 1.3.1 ) = 1 ( expected: 1 )
Failed: bumped( 1.3.1.1 , 13.1.2 ) = 0 ( expected: 1 )
So clearly this is not an optimal solution, but it may get you where you need to go. If you are looking for something that is correct all the time, consider the logic discussed above.