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Postings from June 2003
Kurt Starsinic <kstar@cpan.org> writes: >On May 28, Mark-Jason Dominus wrote: >> Rafael Garcia-Suarez <rgarciasuarez@free.fr>: >> > setbuf/setvbuf aren't available with a PerlIO-enabled perl. >> >> Thanks. >> >> Here's my problem. I want two processes to access the same (small) >> file concurrently. Process A reads part of the file. Process B >> modifies part of the file. Then process A wants to see the change. >> But it can't, because the block it just read is buffered, and >> subsequent reads are all coming from the buffer, which records the >> state of the file before the change, instead of from the real file. >> >> I thought my choices were >> >> a) use setvbuf() to discard the buffer, perhaps temporarily, or As Nick C has said, as far as I know once you have called setvbuf() it is done and all future reads are unbuffered (if that is what you set). >> >> b) discard the buffered I/O system entirely and rewrite everything in >> terms of sysread(), effectively reimplementing the entire buffered I/O >> subsystem in Perl. >> >> But now it appears that my only choice is (b). This isn't very >> attractive. Is there some other option I've overlooked? seek(FH,0,1); # re-position here Will discard the buffer contents on a read stream. > > How about mmap(), or closing and re-opening the read() filehandle? I wonder if :mmap layer has finaly found a use? > > - Kurt -- Nick Ing-Simmons http://www.ni-s.u-net.com/