* bash
[OK] Input: 2	-> Output:  (Expect: )
[OK] Input: .2	-> Output:  (Expect: )
[OK] Input: ..2	-> Output:  (Expect: )
[OK] Input: 2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 2..1	-> Output:  (Expect: )
[OK] Input: version2	-> Output:  (Expect: )
[OK] Input: version2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 22.11	-> Output: 22.11 (Expect: 22.11)
[OK] Input: 2.1.0	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: 2.1.10	-> Output: 2.1.10 (Expect: 2.1.10)
[OK] Input: 2.10.0	-> Output: 2.10.0 (Expect: 2.10.0)
[OK] Input: 22.1.0	-> Output: 22.1.0 (Expect: 22.1.0)
[OK] Input: 33.22.11	-> Output: 33.22.11 (Expect: 33.22.11)
[OK] Input: v1.2-3.4.5.6.7	-> Output: 1.2 (Expect: 1.2)
[OK] Input: v1.2.3.4.5.6.7.8	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: v1.2.3-4.5.6-7	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: 2.1.0-39-g4e1ede	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: v2.1.0-39-g4e1ede1	-> Output: 2.1.0 (Expect: 2.1.0)

* dash
[OK] Input: 2	-> Output:  (Expect: )
[OK] Input: .2	-> Output:  (Expect: )
[OK] Input: ..2	-> Output:  (Expect: )
[OK] Input: 2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 2..1	-> Output:  (Expect: )
[OK] Input: version2	-> Output:  (Expect: )
[OK] Input: version2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 22.11	-> Output: 22.11 (Expect: 22.11)
[OK] Input: 2.1.0	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: 2.1.10	-> Output: 2.1.10 (Expect: 2.1.10)
[OK] Input: 2.10.0	-> Output: 2.10.0 (Expect: 2.10.0)
[OK] Input: 22.1.0	-> Output: 22.1.0 (Expect: 22.1.0)
[OK] Input: 33.22.11	-> Output: 33.22.11 (Expect: 33.22.11)
[OK] Input: v1.2-3.4.5.6.7	-> Output: 1.2 (Expect: 1.2)
[OK] Input: v1.2.3.4.5.6.7.8	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: v1.2.3-4.5.6-7	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: 2.1.0-39-g4e1ede	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: v2.1.0-39-g4e1ede1	-> Output: 2.1.0 (Expect: 2.1.0)

* busybox(static-sh)
[OK] Input: 2	-> Output:  (Expect: )
[OK] Input: .2	-> Output:  (Expect: )
[OK] Input: ..2	-> Output:  (Expect: )
[OK] Input: 2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 2..1	-> Output:  (Expect: )
[OK] Input: version2	-> Output:  (Expect: )
[OK] Input: version2.1	-> Output: 2.1 (Expect: 2.1)
[OK] Input: 22.11	-> Output: 22.11 (Expect: 22.11)
[OK] Input: 2.1.0	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: 2.1.10	-> Output: 2.1.10 (Expect: 2.1.10)
[OK] Input: 2.10.0	-> Output: 2.10.0 (Expect: 2.10.0)
[OK] Input: 22.1.0	-> Output: 22.1.0 (Expect: 22.1.0)
[OK] Input: 33.22.11	-> Output: 33.22.11 (Expect: 33.22.11)
[OK] Input: v1.2-3.4.5.6.7	-> Output: 1.2 (Expect: 1.2)
[OK] Input: v1.2.3.4.5.6.7.8	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: v1.2.3-4.5.6-7	-> Output: 1.2.3 (Expect: 1.2.3)
[OK] Input: 2.1.0-39-g4e1ede	-> Output: 2.1.0 (Expect: 2.1.0)
[OK] Input: v2.1.0-39-g4e1ede1	-> Output: 2.1.0 (Expect: 2.1.0)

* Major/Minor/Patch version
Input: v2.1.0-39-g4e1ede1 -> Output: Major:2, Minor:1, Patch:0

grep (GNU grep) 3.4