Questions tagged [fifo]

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Amazon::SQS::Simple MessageGroupId on a FIFO Queue

I need help on how to pass the MessageGroupId as parameter using the CPAN Module Amazon::SQS::Simple I tried the following : my $messageGroupId = 1; my $q = $sqs->GetQueue('http://queue.amazonaws.com/' . $queue_name); $q->{MessageGroupId} = $messageGroupId; $q->SendMessage($message); I also tried p...
Cadz
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When I cross data from a slow clock to a fast clock domain, wouldn't the stretched data be an issue for processing?

I want to use two fifo's asynchronously in series to cross from a slow-clock domain to a fast-clock domain. I have a slow clock (x MHz) that I need a multiple of (either 2x, 3x, 4x, or 6x). I won't have an issue with overflow on the first fifo since the next fifo will be set to a faster clock. Howev...
DeadSupra
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3

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NRF24L01+ RX Mode and Flush

I have been trying to write my own code for NRF24L01+. I have a problem and I can not solve it As a receiver, I use STM32F103C8T6 and as a transmitter I use Arduino Uno. The problem is related to RX Operation. As I've mentioned above, As a receiver, I use STM32F103C8T6 and as a transmitter I use Ar...
PIC16F84A
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Scheduling strategy behind AWS Batch

I am wondering what the scheduling strategy behind AWS Batch looks like. The official documentation on this topic doesn't provide much details: The AWS Batch scheduler evaluates when, where, and how to run jobs that have been submitted to a job queue. Jobs run in approximately the order in which the...
lenawal
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BlockingCollection multiple consumers per group FIFO

I have a single producer that insert messages into a BlockingCollection. The messages in the collection each have a groupId. The count of different groupIds is dynamic. The messages per group must be processed in FIFO order. The work that the consumers do is a small calculation and a database insert...
mibiio
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Reliably reading from a FIFO in NodeJS

I'm writing a NodeJS script which interacts with a 3rd party application. The third party application will write data to a file for the duration that it's open. I'd like for my NodeJS application to receive this data in real-time. My script creates a fifo: child_process.spawnSync('mkfifo', [pipePath...
Joshua Walsh
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Which handle to pass to CreateIoCompletionPort, if using IOCP for basic signaling?

Background: As described in this article, Designing Applications for High Performance: Consider using PostQueueCompletionStatus rather than SetEvent API. The latter boosts the target thread’s priority by 1 which may cause it to preempt something else. I am working in C on Windows, and I'd like...
Lou
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Take only first json object from stream with jq, do not touch rest

This thread Split multiple input JSONs with jq helped me to solve one problem. But not other. mkfifo xxs exec 3xxs ## keep open file descriptor echo '{'a':0,'b':{'c':'C'}}{'x':33}{'asd':889}' >&3 jq -nc input
kyb
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Informix: Fifo valuation with SQL/Stored procedures

I am using IDS 10 and I have a simple transaction table with the inventory changes with product ID, transaction time, volume, quantity and price. Is it possible to determine the FIFO valuation solely with SQL/Stored procedures or do I need to use something like Perl with DBI for the cursor handling?...
weismat
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Java ConcurrentMap - Position of Key in Map

I have an interesting problem I would like some help with. I have implemented a couple of queues for two separate conditions, one based on FIFO and the other natural order of a key (ConcurrentMap). That is you can image both queues have the same data just ordered differently. The question I hav...
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headache with named pipes and forks

I need to write program that have construction like this: Parent makes fifo, then fork() child 1 reads message from stdin and writes it to named pipe (FIFO) then in parent process I need to create pipe (unnamed) and another fork() child number 2 reades from FIFO, counts length of message and send nu...
lvp
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FIFO Issue with concurrent processes

PRETEND THEY'RE NOT PARENT AND CHILD PROCESSES EVEN THOUGH THEY ARE. MAKE FIFO: /* Create response FIFO. */ if (mkfifo(RESP_FIFO_NAME, FIFO_MODE) == -1) { if (errno != EEXIST) { fprintf(stderr, 'Server: Couldn’t create %s FIFO.\n', RESP_FIFO_NAME); exit(1); } } Fork: /* 3. Fork the client process....
ICantNameMe
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an enclosing instance that contains Queue.Node is required

So I'm working on a Binary Search Tree and need to do a Level Order Traversal. I will be printing out all the keys that are on the same level. Problem I'm having right now is that I need to create a FIFO Queue. I have the Queue created but when I try to add the node to the queue I keep getting the a...
k3vy w3vy
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Linux select() and FIFO ordering of multiple sockets?

Is there any way for the Linux select() call relay event ordering? A description of what I'm seeing: On one machine, I wrote a simple program which sends three multicast packets, one to each of three different multicast groups. These packets are sent back-to-back, with no delay in between. I.e. se...
Matt
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Bridge Unix domain socket with a FIFO and log file

I need to write a script - preferably a bash script - that will listen on a Unix domain socket and pipe the output to a log file while receiving input through a FIFO. The FIFO / log end is supposed to mimic the style of ii. The script also be able to monitor and react to the input from the FIFO (e.g...
AdamHovorka
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FIFO page replacement algorithm problems

I am writing a program to find page faults using FIFO in C#. The user either provides a 20 character reference string or a random one is generated. The user also inputs the number of frames. So, I am passing in the array of 20 single digit numbers, array of frames, and # of frames to my FIFO functio...
user3015999
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Data Structure for FIFO Implementation When Getting ith Element

I want a data structure that will be fixed size and will work as FIFO. I mean if size exceeds the very first element will be removed. Also after each insertion I want to check the middle element at that structure (i.e. 10th element at size of 21) I consider to use ArrayDeque but Deque interface does...
kamaci
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Verilog FIFO code written with different styles..one not working and another not working.Can someone explain

I have written verilog code for fifo using fillcount to check as the means for checking if it is full or empty. There are 2 versions of the same code. One is whereI have a seprate always always block for reading,writing,empty /full ,fillcount,and one for incrementing the pointers.This works fine,I h...
mjaju
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Alternative to the poll function to check new data in a FIFO

I'm writing a method to check if there is new data in a FIFO opened in RDONLY mode. Until now I was using the poll() function but I realized that the kernel on which the code will run doesn't have this function and it implements a subset of the Linux functionality and a subset of the POSIX functiona...
Nicola
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249

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Multiple unix pipes not working

This first pipeline works fine (printing 'c'): echo 'a' | sed 's/a/b/' | sed 's/b/c/' This one does not do what I expect (nothing gets printed when I feed an 'a' into my fifo ): mkfifo fifo; cat fifo | sed 's/a/b/' | sed 's/b/c/' However, if I remove the second 'sed' command from the latter pipelin...
Sridhar-Sarnobat
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work with fifo in c++ ( blocking read)

What I want to do : 1.Create and open for writing in.fifo by process1 2.Open in.fifo for reading in process2 3.Write from cin to in.fifo by process1 line 4.Read and cout line by process2 5.When input 'exit' to cin (process2), it closed file in.fifo, delete it and exit 6.process2 exit, because in....
fedden
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How to implement a timeout in open/write function

I want to use named fifo channel and I want to implement a timeout when I write in this fifo. fd = open(pipe, O_WRONLY); write(fd, msg, len); Program is blocked by function open, so using the function select will not work. Thanks.
Kosterio
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Loss of data in a FIFO pipe?

I have a python process writing to a named pipe, and a C++ program reads it. (I create the pipes in C++). Well, it seems to work fine. However, sometimes I notice that there's loss of data. The data is not detected by the reader! Am I doing something wrong? Here's how I am creating the pipes: void c...
Luis Cruz
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Reading/Writing a named pipe in Java? [duplicate]

This question already has an answer here: Not able to read from named pipe in Java 1 answer How do I read and write to a FIFO pipe using Java? Also, is the reading method blocking? I need to read a pipe and I need the program to wait until there's something in the pipe. Thanks in advance.
Luis Cruz
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Write data to FUSE named pipe

I've created a virtual filesystem that presents its outputs as read-only named pipes (i.e., S_IFIFO). As far as getattr is concerned, my host is showing that the permission mode is set correctly. However, when I attempt to open the pipe (e.g., cat my_fuse_mount/my_pipe), it apparently does so but no...
Xophmeister
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Starting fifo at the startup Linux fedora

I have been using fifos for controlling mpg123 player, there every-time I need to execute these 3 commands mkfifo a // create fifo cat > a & //to run it indefinately mypid=$! //assign some dummy pid I want to put this into some script which would execute it at the boot, i wrote a script containing t...
Kalu DADA
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How do I flush a FIFO after reading it?

I have two executable, sender and receiver. receiver will fork 4 sender ( calling exec('sender') immediately after fork() ) and wait to receive data from each senders. ( the order of receiving data does not matter. ) sender: // executed by four different processes, forked from the `receiver` fifo_w...
Yun-Chih Chen
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CircularFIFOQueue : Using get method

I am trying to implement a CircularFifoQueue in java. Queue rssififo = new CircularFifoQueue(2); I am getting consfused on how to use the get method of the CircularFifoQueue API. The API states public E get(int index) Returns the element at the specified position in this queue. Parameters: index -...
srai
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FIFO receiving numbers (C code)

So I have a FIFO file that I made with mkfifo() function in terminal and I'm sending data with : echo'12.5 123 5 -2.1' > rndfifo My program needs to read those numbers and put them in a array so that I can use them later . I currently only succeeded in creating a program that reads those numbers an...
Nikola
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How to write messages into a FIFO and read it from another process simultaneously

In Unix system, I just knew that we could use FIFO file for communication between two processes and I've tested it with C projects. Now I'm wondering if we can do something like this: Open two terminals. Use one to write messages into a FIFO and use the other to read it. When I put something into th...
Yves
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How to make a process ring with fork and mkfifo?

Currently I'm learning C and I'd like to make a ring of n childs process with forks and pipes where n is a number entered in argument. Each child could communicate with the next child in two directions like this: p1 --->--- p2 ------ p4 ---
Goolger
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open FIFO for write returns “No such device or address”

I want to create a server process and a client process -for an optional class assignment- and make them communicate with each other. The professor told us that: 1)we must use O_NONBLOCK 2)we must create 2 FIFOs, one for reading only and one for writing only 3)we can't use sockets So, I created 2 F...
Fotis Sk
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FIFO in While loop stucks and waits for read

Server sends its PID to client, client gets and sends SIGUSR1 signal in a loop, so i have handler for that in server code. In theory it needs to get signal and create some random matrix to client back.Client receives Server PID but it never sends matrix to client for some reason. It waits and inse...
opricnik
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Multiples modules reading same fifo

Is it possible to instantiate multiple modules to read from the same fifo assuming they are not reading at the same time, but take turns?? For example: int _tmain(int argc, _TCHAR* argv[]) { sc_fifo PacketTx(24); sc_fifo PacketRx(20); Transmit t1('Transmit'); t1.PacketRx(PacketRx); t1.PacketTx(Packe...
Javia1492
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650

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Using os.open() and .read() on a named pipe in python2.7 results in AttributeError

I'm using Python2.7 and my operating system is Ubuntu14.04. In my python code I'm using fifo = os.open('fifo', os.O_NONBLOCK | os.O_RDONLY) to open a named pipe. I then use string = fifo.read(7) to read seven characters from that pipe. Before running the code I create the pipe in the command line wi...
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AWS: SQS FIFO TPS limit per message group

From the AWS SQS documentation for FIFO queues it says: FIFO queues also provide exactly-once processing but are limited to 300 transactions per second (TPS). ... FIFO queues support message groups that allow multiple ordered message groups within a single queue. ... Messages that belong to the sam...
Alex Q
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270

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Is there a fixed size Deque which removes old elements in Java?

I need a queue like CircularFifoQueue in Apache Commons but with the ability to iterate elements backward. I.e. I need to insert elements in a fixed size queue with auto remove of old elements. But I need to iterate elements starting from the youngest element. Is there something available in Java?
Alexandr
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How can I monitor a FIFO?

I want to debug an issue between two processes ideally by setting up a read-only terminal window of that traffic. Is this something I can simply use existing, standard linux utilities for? The FIFO lives at /run/myfifo and is created in one of the processes with: /* Create a FIFO if one doesn't alr...
tarabyte
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CircularFifoQueue doesn't work inside the method, what to use instead?

I need to write the method which let to store always last 10 (the newset) elements and only 10.I have tried to use CircularFifoBuffer.It works perfectly usee like this: import java.util.ArrayList; import java.util.List; import java.util.Queue; import org.apache.commons.collections4.queue.CircularFi...
agathach
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142

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bash/python stop reading from fifo

I'm trying to get a short python script to read from a fifo under bash/linux and then stop when a certain word is received. i've done the following in main.py import 'sys' while True: line = sys.stdin.readline().rstrip() sys.stdout.write(line + ' read\n') if line=='STOP': break sys.stdout.write('fin...
ehrt1974

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