10-12-2005
UNIX Pipe
Hi ,
I want to understand how the PIPE works in unix . Precisely what I am doing is this .
1. Creating a Named PIPE with the command
mknod sqlldr.dat p
2. Directing a file output to the PIPE file in the background
cat abc > sqlldr.dat
3.SQL Loader in oracle is reading the data from this .
Now I want to undertsnad how it's really working ?
My concern is file abc is going to be a big one . Does this cause any memory problem
Links to how pipe works will be helfful
Does any body has a idea of reading a PIPE file from utl_file in oracle ?
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PIPE(2) BSD System Calls Manual PIPE(2)
NAME
pipe -- create descriptor pair for interprocess communication
SYNOPSIS
#include <unistd.h>
int
pipe(int fildes[2]);
DESCRIPTION
The pipe() function creates a pipe (an object that allows unidirectional data flow) and allocates a pair of file descriptors. The first
descriptor connects to the read end of the pipe; the second connects to the write end.
Data written to fildes[1] appears on (i.e., can be read from) fildes[0]. This allows the output of one program to be sent to another pro-
gram: the source's standard output is set up to be the write end of the pipe; the sink's standard input is set up to be the read end of the
pipe. The pipe itself persists until all of its associated descriptors are closed.
A pipe whose read or write end has been closed is considered widowed. Writing on such a pipe causes the writing process to receive a SIGPIPE
signal. Widowing a pipe is the only way to deliver end-of-file to a reader: after the reader consumes any buffered data, reading a widowed
pipe returns a zero count.
The generation of the SIGPIPE signal can be suppressed using the F_SETNOSIGPIPE fcntl command.
RETURN VALUES
On successful creation of the pipe, zero is returned. Otherwise, a value of -1 is returned and the variable errno set to indicate the error.
ERRORS
The pipe() call will fail if:
[EFAULT] The fildes buffer is in an invalid area of the process's address space.
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
SEE ALSO
sh(1), fork(2), read(2), socketpair(2), fcntl(2), write(2)
HISTORY
A pipe() function call appeared in Version 6 AT&T UNIX.
4th Berkeley Distribution February 17, 2011 4th Berkeley Distribution