From: Robert Klemme <shortcutter@...>
Date: 2008-03-17T06:45:02+09:00
Subject: Re: script runs ok alone, broken pipe when piped to head?

On 14.03.2008 01:30, Dave Burns wrote:
> On Mar 13, 1:04 pm, Mark Bush <m...@bushnet.org> wrote:
>> Dave Burns wrote:
>>>  so I piped it to head and it bombs:
>>>   ruby -rubygems excelparse.rb stuff.xls|head
>>>  Row: 0 Cell: 0> Dispapp
>>>  Row: 0 Cell: 1> Iprc
>>>  Row: 0 Cell: 2> UH tag
>>>  Row: 0 Cell: 3> Weight
>>>  Row: 0 Cell: 4> Tags removed
>>>  Row: 0 Cell: 5> Disk removed or wiped
>>>  Row: 1 Cell: 0> 80118
>>>  Row: 1 Cell: 1> 1173
>>>  Row: 1 Cell: 2> 961SU
>>>  Row: 2 Cell: 0> 80118
>>>  excelparse.rb:19:in `write': Broken pipe (Errno::EPIPE)
>> The "head" command reads and prints the first 10 lines of input (by
>> default), then closes its input and exits.
>>
>> Your script is thus having it's output stream closed which it isn't
>> expecting.  The broken pipe is to be expected.
> 
> So to get my script to act like a responsible command line citizen,
> I'd need to insert some error handling and return normally when the
> pipe breaks, right?

Well, it depends.  If you consider it an error when the script is not 
able to deliver all output the default behavior is ok.  I usually do not 
bother to deal with this situation because I use head and tail from the 
command line only and I know what to expect there.

Kind regards

	robert