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Postings from September 1999
On Thu, 26 Aug 1999 10:58:07 MDT, "Todd C. Miller" wrote: >test 7 in t/io/dup.pl from perl5.005_61 would seem to fly in the >face of the following from perlfunc: > Duping a filehandle does not take into account any existing > contents of stdio buffers. >And it does fail on 4.4BSD-derived stdio's. A syscall trace shows that >the first read is actually reading both lines so when the dup'd fd >is read from, there's nothing left. > >This doesn't seem like a bug in the 4.4BSD stdio to me. When opening >the file with "+<" the test succeeds. This may be due to the fact that >stdio has optimizations for seeking on files that are _not_ read-write. >This seems to avoid some of the buffering. > >Anyone care to comment? The test has been removed because there appears to be no way to make the behavior completely portable. Perl will still attempt to seek-and-flush before duping a handle, but whether your stdio will cooperate or not is unspecified. It is a crying shame that ANSI did not specify a way to force the "flushing" of input handles to avoid buffering headaches. Does anyone know if C9X does anything about this? Sarathy gsar@activestate.comThread Previous