[NTLUG:Discuss] Extracting a column out of input

[Lance Simmons]

I really value these kinds of threads.  Even though I don't make it to
meetings, this list is very helpful!

On Mon, Jan 25, 2016 at 7:42 PM, Robert Citek <robert.citek at gmail.com> wrote:
> On Sun, Jan 24, 2016 at 7:11 PM, Leroy Tennison
> <leroy.tennison at verizon.net> wrote:
>> dpkg -l | while read col1 col2 col3; do echo $col2; done
>
> That works.
>
>> I was trying
>>
>> for i in `dpkg -l`; do read col1 col2 col3; echo col2; done
>
> The "for" construct doesn't really understand lines nor splitting the
> lines as "while" does.
>
>> while read col1 col2 col3; do echo $col2; done < ls -l
> ...
>> while read col1 col2 col3; do echo $col2; done < `ls -l`
>
> Redirecting (i.e. < or >) is used for files.  To redirect the
> input/output to/from a process, use a pipe.  For example:
>
> $ ls -l  | while read col1 col2 col3; do echo $col2; done
>
>> What am I doing wrong and what should I do?
>
> Your first command looks good to me.  I'd go with that.
>
> Regards,
> - Robert
>
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-- 
Lance Simmons