shell command to truncate/cut a part of string - shell

Question

I have a file with the below contents. I got the command to print version number out of it. But I need to truncate the last part in the version file
file.spec:
Version: 3.12.0.2
Command used:
VERSION=($(grep -r "Version:" /path/file.spec | awk '{print ($2)}'))
echo $VERSION
Current output : 3.12.0.2
Desired output : 3.12.0

Answer 1

There is absolutey no need for external tools like awk, sed etc. for this simple task if your shell is POSIX-compliant (which it should be) and supports parameter expansion:
$ cat file.spec
Version: 3.12.0.2
$ version=$(<file.spec)
$ version="${version#* }"
$ version="${version%.*}"
$ echo "${version}"
3.12.0

Answer 2

Try this:
VERSION=($(grep -r "Version:" /path/file.spec| awk '{print ($2)}' | cut -d. -f1-3))
Cut split string with field delimiter (-d) , then you select desired field with -f param.

Answer 3

You could use this single awk script awk -F'[ .]' '{print $2"."$3"."$4}':
$ VERSION=$(awk -F'[ .]' '{print $2"."$3"."$4}' /path/file.spec)
$ echo $VERSION
3.12.0
Or this single grep
$ VERSION=$(grep -Po 'Version: \K\d+[.]\d+[.]\d' /path/file.spec)
$ echo $VERSION
3.12.0
But you never need grep and awk together.

Answer 4

if you only grep single file, -r makes no sense.
also based on the output of your command line, this grep should work:
grep -Po '(?<=Version: )(\d+\.){2}\d+' /path/file.spec
gives you:
3.12.0
the \K is also nice. worked for fixed/non-fixed length look-behind. (since PCRE 7.2). There is another answer about it. but I feel look-behind is easier to read, if fixed length.