tiny patch to prevent head from closing pipes
Jilles Tjoelker
jilles at stack.nl
Sun Aug 29 21:00:45 UTC 2010
On Sat, Aug 28, 2010 at 06:42:29PM +0400, Anonymous wrote:
> Alexander Best <arundel at freebsd.org> writes:
> > 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
Even easier (and avoiding mangling through read) is
svn log | { head; cat >/dev/null; }
Beware that the cat command will not necessarily get all of the input.
head may buffer reads and it is unable to push the extra data back onto
the pipe.
> But I think subversion should
I think Subversion should not print an error message for broken pipe on
its stdout.
> > 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?
--
Jilles Tjoelker
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