10-24-2007
It should be simpler than the way you have it....
all that "|" means is give the write end to stdout of the left hand process and the read end to stdin for the right hand process.
but apart from > and <, the stdin/stdout/stderr should just be left alone.
To do ">" you just open a file and use it for stdout, end of story.
I personally would parse the line into a tree where each node is what I want to run in one process, each node would have pointers to where they get their stdin/stdout/stderr from.
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LEARN ABOUT OPENDARWIN
pipe
PIPE(2) BSD System Calls Manual PIPE(2)
NAME
pipe -- create descriptor pair for interprocess communication
SYNOPSIS
#include <unistd.h>
int
pipe(int *fildes);
DESCRIPTION
The pipe() function creates a pipe, which is an object allowing unidirectional data flow, and allocates a pair of file descriptors. The
first descriptor connects to the read end of the pipe, and the second connects to the write end, so that 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 program: the source's standard output is set
up to be the write end of the pipe, and the sink's standard input is set up to be the read end of the pipe. The pipe itself persists until
all 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.
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:
[EMFILE] Too many descriptors are active.
[ENFILE] The system file table is full.
[EFAULT] The fildes buffer is in an invalid area of the process's address space.
SEE ALSO
sh(1), read(2), write(2), fork(2), socketpair(2)
HISTORY
A pipe() function call appeared in Version 6 AT&T UNIX.
4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution