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Full Discussion: Non-blocking pipe
Top Forums Shell Programming and Scripting Non-blocking pipe Post 302285962 by Corona688 on Tuesday 10th of February 2009 02:43:52 AM
Old 02-10-2009
The && will cause the shell to wait before running the command after it, and should any of them fail, none of the ones after it will run. && is a conditional, it's not a background statement. Also, is there any particular reason that string of commands is all in one line? And what is 'echo exec' for, did you mean for that to be without the echo?

I don't think there's any point trying to open it as a FD in the shell if you're trying to save time, since the shell will wait for the reader to open the pipe anyway. Once it does, all three processes will get the same pipe, which I doubt is what you want. at which point all three processes will get copies of the same pipe, not queue up.

This sort of code, on the other hand, will wait for the pipe, launch a process, then immediately wait on the pipe again without waiting for the launched process to finish:
Code:
echo a > fifo &
echo b > fifo &
echo c > fifo &

 

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PIPE(2) 							System Calls Manual							   PIPE(2)

NAME
pipe - create an interprocess channel SYNOPSIS
#include <u.h> #include <libc.h> int pipe(int fd[2]) DESCRIPTION
Pipe creates a buffered channel for interprocess I/O communication. Two file descriptors are returned in fd. Data written to fd[1] is available for reading from fd[0] and data written to fd[0] is available for reading from fd[1]. After the pipe has been established, cooperating processes created by subsequent fork(2) calls may pass data through the pipe with read and write calls. The bytes placed on a pipe by one write are contiguous even if many processes are writing. Write boundaries are preserved: each read terminates when the read buffer is full or after reading the last byte of a write, whichever comes first. The number of bytes available to a read(2) is reported in the Length field returned by fstat or dirfstat on a pipe (see stat(2)). When all the data has been read from a pipe and the writer has closed the pipe or exited, read(2) will return 0 bytes. Writes to a pipe with no reader will generate a note sys: write on closed pipe. SOURCE
/sys/src/libc/9syscall SEE ALSO
intro(2), read(2), pipe(3) DIAGNOSTICS
Sets errstr. BUGS
If a read or a write of a pipe is interrupted, some unknown number of bytes may have been transferred. When a read from a pipe returns 0 bytes, it usually means end of file but is indistinguishable from reading the result of an explicit write of zero bytes. PIPE(2)
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