tiny patch to prevent head from closing pipes

jhell jhell at DataIX.net
Sun Aug 29 20:54:49 UTC 2010

On 08/28/2010 12:01, Alexander Best wrote:
> On Sat Aug 28 10, Anonymous wrote:
>> Alexander Best <arundel at freebsd.org> writes:
>>> hi there,
>>> i just had subversion complain about a broken pipe while piping its output
>>> through awk straight to head [1]. i decided to add a switch to head which will
>>> tell it to never close a pipe unless the input has stopped [2].
>> You can do same with sh(1), e.g.
>>   $ svn log | (IFS=; while read li; do [ $((i+=1)) -le 10 ] && echo "$li"; done)
>> versus
>>   $ svn log | (IFS=; while read li && [ $((i+=1)) -le 10 ]; do echo "$li"; done)
>>   ...
>>   svn: Write error: Broken pipe
>> But I think subversion should
>>> there's probably a much more efficient way of discarding the input without
>>> closing the pipe unless the input ceased. it's just a 5 minute hack in order to
>>> see if people find the idea useful or not. ;)
>> Can you give an example of usefulness that does not involve subversion?
> no, but this should be valid for all applications which return an error if the
> pipe gets closed by the receiving end.
> of course it's possible to implement the features to head i added in form of a
> sh(1) script. i understand that your point is, that there is already a way of
> keeping the pipe open and that the unix philosophy states that no two programs
> should share the same functionality.
> on the other hand you don't really need head and tail at all then, because
> their functionality could also be implemented in form of a script. ;) i hope
> you get my point.
> cheers.
> alex

No offense but patching this would be honoring bad scripting and
encouraging such things to happen more often. If you catch my drift.




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