Date: Fri, 30 Apr 2010 18:06:16 +1000 From: "Murray Taylor" <MTaylor@bytecraft.com.au> To: <freebsd-questions@freebsd.org> Subject: Parent Child SIGPIPE and write problem Message-ID: <E194A4DE220BBE4FAF3AB7C4E7EDA086B4A363@svmailmel.bytecraft.internal>
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I am writing a process that has a parent running as a daemon process
that has to spawn an appropriate child to parse whatever the parent has
in one of several formats (hence the variety of child parsers)
I am getting occasional SIGPIPE errors (and the boring bit is that I
have put in code that I think _should_prevent the SIGPIPE occurring
any comments or guidance welcome ...
parent pseudo code
main()
{
=09daemon
=09while(1)
=09{
=09 get test data
=09 pipe()
=09 fork()
=09 in Parent
=09 read(child->parent pipe) until \n
=09 log string to logfile
=09 write(parent->child pipe) real data to child for
processing
=09 close(parent->child pipe)
=09
=09 read(child->parent pipe) until EOF for result
=09
=09 waitpid(child)
=09 get return code
=09 in Child
=09 set stdin nonblocking so child will inherit
=09 execve the correct parser
=09}
}
child pseudo code
main()
{
=09read cmdline params
=09write(child->parent pipe) my PID
=09read(parent->child pipe) intil EOF
=09process through flex/bison parser
=09write(child->parent pipe) the result
=09return (code)
}
I am catching SIPPIPE in the parent and logging it, and have a=20
test on the parent write for EPIPE and am doing a go-around twice loop
through
the write before giving up.
Murray Taylor
Bytecraft Systems
Special Projects Engineer
P: +61 3 8710 0600
D: +61 3 9238 4275
F: +61 3 9238 4140
--
=20|_|0|_| "Absence of evidence
=20|_|_|0| is not evidence of absence"
=20|0|0|0| Carl Sagan
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