Pipes don't serialize or check for things like two readers and writers. You can have a reader "A" open the pipe with writer "A", and then switch writers on the reader (by starting another writer "B" and THEN closing writer "A"). The reader sees an EOF only if a read attempt is made when no one is WRITING to it. This is further complicated by the fact that two different processes (Reader and writer) are not synched in other ways.

I recommend:

• a lock file to make sure two writers don't touch the pipe at the same time. Make this lock on a separate lock file (no use locking a pipe you just opened if the idea is to not touch the pipe before locking).
• Serialize the communications (have each writer use a unique number). How do you get the unique number? Using the lock file from (1) could be a solution.

I must admit I did not experiment with your code so there might be other reasons (but locking is a good idea if you have the remotest chance that two writers will need to talk at the same time).

-- termix

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.