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IPC - pipes between parent and child process
Post 302473584 by DGPickett on Sunday 21st of November 2010 02:01:25 PM
11-21-2010
Well, it sounds like you need a protocol, or operate your pipes full duplex with at state machine at each end to take care of activities on that overlaid protocol. Decoding & analyzing professors is much more complex than decoding & analyzing an API. 
If you find pipes, sockets, shmem, semaphores, queues and all that a bit restrictive, you can mmap() a file in both processes, creating an area of shared memory, not to be confused with the silly UNIX ipc shared memory that needs root setup and such dusty old stuff, and the nice thing is that you can peek at the mmap90'd file during or after for you edification about what is going on. It is really fast, RAM write snoop invalidating cache fast. You can even have a file for each writer, so there is no ambiguity about who put the file in that state.
If you find pipes, sockets, shmem, semaphores, queues and all that a bit restrictive, you can mmap() a file in both processes, creating an area of shared memory, not to be confused with the silly UNIX ipc shared memory that needs root setup and such dusty old stuff, and the nice thing is that you can peek at the mmap90'd file during or after for you edification about what is going on. It is really fast, RAM write snoop invalidating cache fast. You can even have a file for each writer, so there is no ambiguity about who put the file in that state.
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LEARN ABOUT MOJAVE
ipcs
IPCS(1) BSD General Commands Manual IPCS(1) NAME
ipcs -- report System V interprocess communication facilities status SYNOPSIS
ipcs [-abcMmopQqSsTt] DESCRIPTION
The ipcs utility provides information on System V interprocess communication (IPC) facilities on the system. The options are as follows: -a Show the maximum amount of information possible when displaying active semaphores, message queues, and shared memory segments. (This is shorthand for specifying the -b, -c, -o, -p, and -t options.) -b Show the maximum allowed sizes for active semaphores, message queues, and shared memory segments. The ``maximum allowed size'' is the maximum number of bytes in a message on a message queue, the size of a shared memory segment, or the number of semaphores in a set of semaphores. -c Show the creator's name and group for active semaphores, message queues, and shared memory segments. -M Display system information about shared memory. -m Display information about active shared memory segments. -o Show outstanding usage for active message queues, and shared memory segments. The ``outstanding usage'' is the number of messages in a message queue, or the number of processes attached to a shared memory segment. -p Show the process ID information for active semaphores, message queues, and shared memory segments. The ``process ID information'' is the last process to send a message to or receive a message from a message queue, the process that created a semaphore, or the last process to attach or detach a shared memory segment. -Q Display system information about messages queues. -q Display information about active message queues. -S Display system information about semaphores. -s Display information about active semaphores. -T Display system information about shared memory, message queues and semaphores. -t Show access times for active semaphores, message queues, and shared memory segments. The access times is the time of the last con- trol operation on an IPC object, the last send or receive of a message, the last attach or detach of a shared memory segment, or the last operation on a semaphore. If none of the -M, -m, -Q, -q, -S, or -s options are specified, information about all active IPC facilities is listed. RESTRICTIONS
System data structures may change while ipcs is running; the output of ipcs is not guaranteed to be consistent. BUGS
This manual page is woefully incomplete, because it does not at all attempt to explain the information printed by ipcs. SEE ALSO
ipcrm(1) AUTHORS
Thorsten Lockert <tholo@sigmasoft.com> BSD
June 18, 1994 BSD