bash regex to match semantic version number -

bash regex to match semantic version number -

i have following:

versionnumber=$(sw_vers -productversion) # finds version number versionshort=${versionnumber:0:4} # cutting string 1 decimal place calculation

which works when versions this:

10.9.2 10.9.5

but not match

10.10.3

as homecoming only

10.1

but want versionshort set

10.10

i wanting match major version, first dot , minor version above.

regexpless solution - cutting off lastly dot , whatever follows it:

versionshort=${versionnumber%.*}

regex bash