03-31-2013
That you can see their output means they're not being redirected properly.
You must dup2 the read-end of the previous pipe over the stdin of the process, and dup2 the write-end of the next pipe over the stdout of the process, for it to be part of the pipe chain. Otherwise its output will go direct to the terminal like everything else.
You must also close all original pipes in the child, leaving only the duplicates, or they may freeze when they're done instead of quitting.
Try simplifying your example. Right now it's very large and complex. Try something that just uses arrays for input instead of a full parser, then add it back on once you get it to work.
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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