Hi again, I'm moving ahead a little bit and have done some basic tests with tapes but now have something I don't understand.
I'm trying to "concatenate" two tapes into one named pipe, and then read the pipe, hoping thereby to read the two tapes at once (trying to emulate the z/OS JCL concatenation concept). Here's my logic, which is not working as I'll explain in a minute. My thinking is that I can write to the pipe sequentially and read it sequentially, but it appears not to work that way. pe...@sydvs002:~> sudo dd if=/dev/rtibm0 of=pipe & pe...@sydvs002:~> sudo dd if=/dev/rtibm1 of=pipe & pe...@sydvs002:~> sudo dd if=pipe of=packages & When I do this, the first and third commands work as expected, i.e. the contents of the first tape are copied into the disk file "packages". The second command didn't block, but went ahead and copied zero bytes into the disk file (it really should have copied about 30MB, so why it didn't is a small mystery but not as large as its not waiting for the first command). I expected the second command to block, or be queued behind the first command. On reflection, I decided that expectation was wrong, i.e. there is no reason for the second command to block as I was expecting. Am I right to think that I'll have to implement some sort of queuing mechanism if I want the input files to queue into the pipe and be read sequentially? Or have I still a basic misunderstanding of queueing with named pipes, such that named pipes can queue input commands in the way I'm expecting? If I have to do my own queueing, I'm sure something simple like cmd1 && cmd2 && cmd3 etc. will be OK, but I wanted to make sure I've not misunderstood the available facilities first. thanks again for your input, best regards Peter Peter Bishop HP Enterprise Services APJ Mainframe Capability & Engineering +61 2 9012 5147 office | +61 2 9012 6620 fax | [email protected]<mailto:[email protected]> 36-46 George St | Burwood | NSW 2134 Australia ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
