Re: [gentoo-user] OT: Extracting year from data, but honour empty lines

[Daniel Frey]

On 05/12/18 00:09, Paul Colquhoun wrote:
> On Saturday, 12 May 2018 12:05:47 PM AEST Paul Colquhoun wrote:
>> You can add an alternate regular expression that matches the blank lines,
>> but the '-o' switch will still stop that match from being printed as it is
>> an 'empty' match. The trick is to modify the data on the fly to add a space
>> to the empty lines. I have also added the '-E' switch to make the regular
>> expression easier.
>>
>> sed -e 's/^$/ /'  YOUR_DATA_FILE  | grep -o -E '([0-9]{4}|^[[:space:]]*$)'
>
>
> If there is no other type of data in the file, just "lines with dates" & "blank
> lines", then it can be done with just the 'sed' command on it's own:
>
> sed -e 's/.*\([0-9][0-9][0-9][0-9]\).*/\1/' YOUR_DATA_FILE
>
>

Thanks to everyone for the replies. Yes, the data is only lines with
mangled dates and spaces, and come to think of it, I was using sed the
first go-around.

Now that I'm more awake hopefully this process will go a bit easier.

Thanks again everyone.

Dan