Replace Strings Using Sed And Regex
For complying sample question, simply
sed 's/^# //' filewill suffice, but if there is a need to remove the comment only on some lines containing a particular regex, then you could use conditionnal address:
sed '/regex/s/^# //' fileSo every lines containing regex will be uncomented (if line begin with a #)
... where regex could be [0-9] as:
sed '/[0-9]/s/^# //' filewill remove # at begin of every lines containing a number, or
sed '/[0-9]/s/^# \?//' fileto make first space not needed: #one two 12, or even
sed '/[0-9]$/s/^# //' filewill remove # at begin of lines containing a number as last character. Then
sed '/12$/s/^# //' filewill remove # at begin of lines ended by 12. Or
sed '/\b\(two\|three\)\b/s/^# //' filewill remove # at begin of lines containing word two or three.