Bash - an odd problem using sed or awk or for

[JD]

On 11/29/2012 04:33 PM, John Horne wrote:
> Hello,
>
> I have a bash script in which a variable is set to one or more lines of
> text. What I want is to remove any lines up to and including a blank
> line (or alternatively to echo all the lines after the last blank line).
> There may be zero or more blank lines, and the blank lines need not be
> consecutive. If there is no blank line, then all the lines should be
> shown. If the last line is blank, then nothing should be shown. So for
> example the variable may contain:
>
> ============ (the '=' are not part of the variable)
> abc def
>
> hijk
> xyz
> ============
>
> So in this case what is wanted is:
>
> ============
> hijk
> xyz
> ============
>
> to be shown.
>
> I tried something like:
>
>     echo "$XX" | sed -e '/./,/^$/d'
>
> but this didn't display anything. (Where XX is the variable.)
> I also tried using a 'for' loop but again this displayed nothing:
>
>     opt=""
>     IFS=$'\n'
>     for n in $XX; do test -z "$n" && opt="" || opt="$opt $n"; done
>
> (Echoing $opt after this shows that it contains nothing.) I'm not sure
> why but even using a for loop just to show it had seen a blank line
> didn't work either (using something like 'test -z "$n" && echo found').
> My understanding was that by setting IFS to a newline, then the 'for'
> loop should see the blank line and just set '$n' to the null string. We
> should then be able to test on that.
>
> Ideally what I am looking for is a snappy one line 'sed' or 'awk'
> command to handle this :-) Unfortunately at the moment I seem to be
> getting nowhere though, even with the 'for' loop.
>
>
>
> Thanks,
>
> John.
>
John, this is easily accomplished, but you are not telling us
where and from what source is your variable being set.
For example, are you reading the lines in from a file
or from stdin?
If so, then I would get rid of lines containing any space(s) as follows:

while read line; do
set $line
[ $# -lt 2 ] && echo $line
done < SomeFile

If reading from stdin, then you only need
done (without the < SomeFile).

It will print only the lines that lack a space.