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Full Discussion: UNIX Pipe
Top Forums UNIX for Dummies Questions & Answers UNIX Pipe Post 86248 by jim mcnamara on Wednesday 12th of October 2005 01:46:32 PM
Old 10-12-2005
a pipe is an intermediate file that allows to separate process to communicate.
The file uses FIFO I/O - first-in first-out. The last thing written to the file is the first thing read from the file.

I don't see any advantage to invoking sqlldr with a pipe. In fact, it may be a problem because pipes have a limit on "record" size - see /usr/include/limits.h _POSIX_PIPE_BUF and PIPE_BUF - and tables with several long columns will cause a problem with overflow.

One way pipes are really useful is to have two separate Oracle sessions comminuicating to one another using DBMS_PIPE
 

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FIFO(7) 						     Linux Programmer's Manual							   FIFO(7)

NAME
fifo - first-in first-out special file, named pipe DESCRIPTION
A FIFO special file (a named pipe) is similar to a pipe, except that it is accessed as part of the file system. It can be opened by multi- ple processes for reading or writing. When processes are exchanging data via the FIFO, the kernel passes all data internally without writ- ing it to the file system. Thus, the FIFO special file has no contents on the file system; the file system entry merely serves as a refer- ence point so that processes can access the pipe using a name in the file system. The kernel maintains exactly one pipe object for each FIFO special file that is opened by at least one process. The FIFO must be opened on both ends (reading and writing) before data can be passed. Normally, opening the FIFO blocks until the other end is opened also. A process can open a FIFO in nonblocking mode. In this case, opening for read only will succeed even if no-one has opened on the write side yet, opening for write only will fail with ENXIO (no such device or address) unless the other end has already been opened. Under Linux, opening a FIFO for read and write will succeed both in blocking and nonblocking mode. POSIX leaves this behavior undefined. This can be used to open a FIFO for writing while there are no readers available. A process that uses both ends of the connection in order to communicate with itself should be very careful to avoid deadlocks. NOTES
When a process tries to write to a FIFO that is not opened for read on the other side, the process is sent a SIGPIPE signal. FIFO special files can be created by mkfifo(3), and are indicated by ls -l with the file type 'p'. SEE ALSO
mkfifo(1), open(2), pipe(2), sigaction(2), signal(2), socketpair(2), mkfifo(3), pipe(7) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-12-03 FIFO(7)
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