broken pipe


 
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# 1  
Old 11-16-2011
broken pipe

I know what causes 'broken pipe' errors, but I can't understand why I can get it (only occasionally) with my example:

Code:
ps -ef | grep "\./ans$" | grep -v grep

Basically I'm searching the ps output looking for the process I'm interested in and excluding the process that is grepping for the answer.

Actually I'm doing all this inside a perl one liner shown below:

Code:
perl -e '$_=`ps -ef | grep \"\./ans$\" | grep -v grep`; ($_)=(split(" "))[1]; kill TERM, $_ if $_;'

Very infrequently it fails, but of course I need it to 'never' fail!

If the cause is 'a process writing into a closed pipe', it can happen in two places, but I can't fathom why either the 2nd grep would close the pipe on the first one, or that the first grep would close the pipe on the 'ps'.

I would expect the ps to send and EOF and close the pipe on the first grep who would in turn close the pipe on the second grep.

Can anyone explain my dilema?

TIA
Fulko
Moderator's Comments:
Mod Comment Please use code tags!

Last edited by vbe; 11-16-2011 at 10:41 AM.. Reason: code tags rm fonts
# 2  
Old 11-16-2011
I'm not sure. They ought to finish, yes. Perhaps it's memory or limits problems?

Here's a tip though: grep "\./[a]ns$" won't need "grep -v grep" since the regex will no longer match itself.
# 3  
Old 11-16-2011
Thanks for your suggestion.

I had recoded it (simplified) it anyway which eliminated the two pipes (and the processes that went with it).

But my problem remained, which told me... the sample code I provided above was NOT causing the 'broken pipe' but something ELSE that was going on on my system at _apparently_ the same time as that line was executing
(leading me on the wild goose chase).

I've since narrowed it down to another application that was not 'shutting down as gracefully as it could have', and THAT'S where the 'broken pipe' was occurring.

'My bad' as they say. Smilie
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