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• Behavior of a pipe after a fork()

  - by Steve Melvin

  When reading about pipes in Advanced Programming in the UNIX Environment, I noticed that after a fork that the parent can close() the read end of a pipe and it doesn't close the read end for the child. When a process forks, does its file descriptors get retained? What I mean by this is that before the fork the pipe read file descriptor had a retain count of 1, and after the fork 2. When the parent closed its read side the fd went to 1 and is kept open for the child. Is this essentially what is happening? Does this behavior also occur for regular file descriptors?

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• Pipe ffmpeg to oggenc(2) with .NET

  - by acidzombie24

  I am trying to encode ogg files at -q 6/192k. ffmpeg doesnt seem to be listenting to my command ffmpeg -i blah -acodec vorbis -ab 192k -y out.ogg So i would like to use the recommended ogg encoder. It says the input must be wav or similar. I would like to pipe a wav from ffmpeg to ogg. However not only am i unsure if oggenc2 will accept input from stdin, i have no idea how to pipe one process to another inside of .net using the Process class.

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• Django + WebKit = Broken pipe

  - by Saosin

  I'm running the Django 1.2 development server and I get these Broken Pipe error messages whenever I load a page from it with Chrome or Safari. My co-worker is getting the error as well when he loads a page from his dev server. We don't have these errors when using Opera or Firefox. Traceback (most recent call last): File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/core/servers/basehttp.py", line 281, in run self.finish_response() File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/core/servers/basehttp.py", line 321, in finish_response self.write(data) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/django/core/servers/basehttp.py", line 417, in write self._write(data) File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 300, in write self.flush() File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 286, in flush self._sock.sendall(buffer) error: [Errno 32] Broken pipe Can anyone help me out? I'm going crazy over this!

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• How to rate-limit a pipe under linux ?

  - by Frédéric Grosshans

  Is there a filter which I could use to rate-limit a pipe on linux? If this exists, let call it rate-limit, I want to be able to type in a terminal something like cat /dev/urandom | rate-limit 3 -k | foo in order to send a a stream of random bytes to foo's standard input at a rate (lower than) 3 kbytes/s.

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• C Named pipe (fifo). Parent process gets stuck

  - by Blitzkr1eg

  I want to make a simple program, that fork, and the child writes into the named pipe and the parent reads and displays from the named pipe. The problem is that it enters the parent, does the first printf and then it gets weird, it doesn't do anything else, does not get to the second printf, it just ways for input in the console. #include <string.h> #include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> void main() { char t[100]; mkfifo("myfifo",777); pid_t pid; pid = fork(); if (pid==0) { //execl("fifo2","fifo2",(char*)0); char r[100]; printf("scrie2->"); scanf("%s",r); int fp; fp = open("myfifo",O_WRONLY); write(fp,r,99); close(fp); printf("exit kid \n"); exit(0); } else { wait(0); printf("entered parent \n"); // <- this it prints // whats below this line apparently its not being executed int fz; printf("1"); fz = open("myfifo",O_RDONLY); printf("2"); printf("fd: %d",fz); char p[100]; int size; printf("------"); //struct stat *info; //stat("myfifo",info); printf("%d",(*info).st_size); read(fz,p,99); close(fz); printf("%s",p); printf("exit"); exit(0); } }

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• Non-blocking pipe using popen?

  - by jldupont

  I'd like to open a pipe using popen() and have non-blocking 'read' access to it. How can I achieve this? (The examples I found were all blocking/synchronous)

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• Using SAS Macro to pipe a list of filenames from a Windows directory

  - by Bazil

  I am trying to amend the macro below to accept a macro parameter as the 'location' argument for a dir command. However I cannot get it to resolve correctly due to the nested quotes issue. Using %str(%') does not work, neither do quoting functions for some reason. The macro will work fine when the filepath has no spaces (eg C:\temp\withnospace) as the middle quotes aren't needed. However I need this macro to work for filepaths with spaces (eg 'C:\temp\with space\'). Please help! %macro get_filenames(location) filename pipedir pipe "dir &location. /b " lrecl=32767; data filenames; infile pipedir truncover; input line $char1000.; run; %mend; %get_filenames(C:\temp\) /* works */ %get_filenames('C:\temp\with space') /* doesnt work */

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• Pipe between two console applications?

  - by ronag

  How can I pipe between two separate console application running in different console windows? e.g. I would like to do something similar to: ffmpeg -i 0.flv -vcodec mpeg4 -f asf -s cif - | vlc - However, I would like to do this from two separate windows, which doesn't work, I guess this is because standard out is local to cmd windows. cmd window 1: ffmpeg -i 0.flv -vcodec mpeg4 -f asf -s cif - cmd window 2: vlc - Is there any way to programmatically achieve this? What exactly does | do behind the scenes?

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• DIY Standing Desk Sports Super Sturdy Galvanized Pipe Legs

  - by Jason Fitzpatrick

  If you’re looking for a standing desk sturdy enough you can tap dance on it this DIY creation features thick pipe legs and a solid oak desktop. Courtesy of designer Jessica Allen, this standing desk can easily support a bank of monitors, heavy equipment, and even your entire body if need be, thanks to a sturdy galvanized plumbing pipe undercarriage and a 1″ thick oak top. We love the clean lines of the desk but we’d be tempted to clutter them up a little with a tower-rack mounted under the desk or on the inside of the thick pipe legs. Hit up the link below to check out the full build log. Have a cool standing desk (or desk tutorial) to share? Sound off in the comments. Steel Pipe Standing Desk HTG Explains: Why Screen Savers Are No Longer Necessary 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full

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• Bash script, read values from stdin pipe

  - by gmatt

  I'm trying to get bash to process data from stdin that gets piped it, but no luck, what I mean is none of the following work: echo "hello world" | test=($(< /dev/stdin)); echo test=$test test= echo "hello world" | read test; echo test=$test test= echo "hello world" | test=`cat`; echo test=$test test= where I want the output to be test=hello world. Note I've tried putting "" quotes around "$test" that doesn't work either.

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• IOError: [Errno 32] Broken pipe

  - by khati

  I got "IOError: [Errno 32] Broken pipe" while writing files in linux. I am using python to read each line a of csv file and then write into a database table. My code is f = open(path,'r') command = command to connect to database p = Popen(command, shell=True, stdin=PIPE, stdout=PIPE, stderr=PIPE, env=env) query = " COPY myTable( id, name, address) FROM STDIN WITH DELIMITER ';' CSV QUOTE '"'; " p.stdin.write(query.encode('ascii')) *-->(Here exactly I got the error, p.stdin.write(query.encode('ascii')) IOError: [Errno 32] Broken pipe )* So when I run this program in linux, I got error "IOError: [Errno 32] Broken pipe" . However this works fine when I run in windows7. Do I need to do some configuration in Linux sever? Any suggestions will be appreciated. Thank you.

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• Linux: Limiting data throughput (pipe) in bytes per second?

  - by sdaau

  Hi all, I was wandering if there is a Linux program that can limit data throughput of a pipe - in actual bytes per second?. From what I gather, applicable for the purposes would be bfr, however, it has been removed from Debian (Removal candidate: bfr) cpipe, however, it seems the lowest resolution it will support is kB/s, meaning that buffer writes can still reach MB/s ([SOLVED] Is there a program to limit terminal pipe speed? - Page 2 - Ubuntu Forums) What I'd want is to be able to specify something like cat example.txt | ratelimit -Bps 100 > /dev/ttyUSB0 ... and actually have a single byte from example.txt sent each 1/100 = 0.01 sec (or 10 ms) to 'output'.. Thanks in advance for any suggestions, Cheers!

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• c# Named Pipe Asynchronous Peeking

  - by KJ Tsanaktsidis

  Hey all, I need to find a way to be notified when a System.IO.Pipe.NamedPipeServerStream opened in asynchronous mode has more data available for reading on it- a WaitHandle would be ideal. I cannot simply use BeginRead() to obtain such a handle because it's possible that i might be signaled by another thread which wants to write to the pipe- so I have to release the lock on the pipe and wait for the write to be complete, and NamedPipeServerStream doesnt have a CancelAsync method. I also tried calling BeginRead(), then calling the win32 function CancelIO on the pipe if the thread gets signaled, but I don't think this is an ideal solution because if CancelIO is called just as data is arriving and being processed, it will be dropped- I still wish to keep this data, but process it at a later time, after the write. I suspect the win32 function PeekNamedPipe might be useful but i'd like to avoid having to continuously poll for new data with it. In the likley event that the above text is a bit unclear, here's roughly what i'd like to be able to do... NamedPipeServerStream pipe; ManualResetEvent WriteFlag; //initialise pipe lock (pipe) { //I wish this method existed WaitHandle NewDataHandle = pipe.GetDataAvailableWaithandle(); Waithandle[] BreakConditions = new Waithandle[2]; BreakConditions[0] = NewDataHandle; BreakConditions[1] = WriteFlag; int breakcode = WaitHandle.WaitAny(BreakConditions); switch (breakcode) { case 0: //do a read on the pipe break; case 1: //break so that we release the lock on the pipe break; } }

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• How to create named pipe acsessible Only on your machin? (VS08 C++)

  - by Ole Jak

  Hello, I have created a program that write video stream to a named pipe on windows, using Visual Studio C++ 2008 . how to be sequre that no one exept programms on this computer can acsess this pipe? npipe = CreateNamedPipe("\\\\.\\pipe\\TestChannel", PIPE_ACCESS_DUPLEX, PIPE_TYPE_MESSAGE | PIPE_WAIT, PIPE_UNLIMITED_INSTANCES , 1024, 1024,5000,NULL);

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• Multithreading: Read from / write to a pipe

  - by Tero Jokinen

  I write some data to a pipe - possibly lots of data and at random intervals. How to read the data from the pipe? Is this ok: in the main thread (current process) create two more threads (2, 3) the second thread writes sometimes to the pipe (and flush-es the pipe?) the 3rd thread has infinite loop which reads the pipe (and then sleeps for some time) Is this so far correct? Now, there are a few thing I don't understand: do I have to lock (mutex?) the pipe on write? IIRC, when writing to pipe and its buffer gets full, the write end will block until I read the already written data, right? How to check for read data in the pipe, not too often, not too rarely? So that the second thread wont block? Is there something like select for pipes? It is possible to set the pipe to unbuffered more or I have to flush it regularly - which one is better? Should I create one more thread, just for flushing the pipe after write? Because flush blocks as well, when the buffer is full, right? I just don't want the 1st and 2nd thread to block.... [Edit] Sorry, I thought the question is platform agnostic but just in case: I'm looking at this from Win32 perspective, possibly MinGW C...

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• Is there any limit to AIX 5.3 pipe size ?

  - by snowflake

  Hello, I'm in trouble while performing cat/tail/head operation on large files on Aix 5.3. When asking for a cat of several 1Go file redirected to another one: cat file1 file2 file3 > outputfile The outputfile is limited to 2Go (cat: output error and result file is 2147483647 bytes) Filesystem is jfs2. I successfully uploaded through ftp 10Go files on the filesystem without problem. I found nothing relevant in etc/security/limits: default: fsize = -1 core = 2097151 cpu = -1 data = 262144 rss = 65536 stack = 65536 nofiles = 20000 ulimit -a core file size (blocks) unlimited data seg size (kbytes) 245759 file size (blocks) unlimited max memory size (kbytes) unlimited open files 2000 pipe size (512 bytes) 64 stack size (kbytes) 32768 cpu time (seconds) unlimited max user processes 2048 virtual memory (kbytes) 278527 The problem does not occur on another AIX 5.3 server, I'm just looking for a different configuration that might be the source of the problem. /etc/security/limits on the server without the problem: default: fsize = -1 core = 2097151 cpu = -1 data = 262144 rss = 65536 stack = 65536 nofiles = 20000 ulimit -a on the server without the problem: core file size (blocks, -c) 1048575 data seg size (kbytes, -d) 131072 file size (blocks, -f) unlimited max memory size (kbytes, -m) 32768 open files (-n) 20000 pipe size (512 bytes, -p) 64 stack size (kbytes, -s) 32768 cpu time (seconds, -t) unlimited max user processes (-u) 262144 virtual memory (kbytes, -v) unlimited

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• IO::Pipe - close(<handle>) does not set $?

  - by danboo

  My understanding is that closing the handle for an IO::Pipe object should be done with the method ($fh->close) and not the built-in (close($fh)). The other day I goofed and used the built-in out of habit on a IO::Pipe object that was opened to a command that I expected to fail. I was surprised when $? was zero, and my error checking wasn't triggered. I realized my mistake. If I use the built-in, IO:Pipe can't perform the waitpid() and can't set $?. But what I was surprised by was that perl seemed to still close the pipe without setting $? via the core. I worked up a little test script to show what I mean: use 5.012; use warnings; use IO::Pipe; say 'init pipes:'; pipes(); my $fh = IO::Pipe->reader(q(false)); say 'post open pipes:'; pipes(); say 'return: ' . $fh->close; #say 'return: ' . close($fh); say 'status: ' . $?; say q(); say 'post close pipes:'; pipes(); sub pipes { for my $fd ( glob("/proc/self/fd/*") ) { say readlink($fd) if -p $fd; } say q(); } When using the method it shows the pipe being gone after the close and $? is set as I expected: init pipes: post open pipes: pipe:[992006] return: 1 status: 256 post close pipes: And, when using the built-in it also appears to close the pipe, but does not set $?: init pipes: post open pipes: pipe:[952618] return: 1 status: 0 post close pipes: It seems odd to me that the built-in results in the pipe closure, but doesn't set $?. Can anyone help explain the discrepancy? Thanks!

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• FreeBSD Traffic Shaping

  - by alexus

  Hi I'm trying to do traffic shaping with FreeBSD, here are my rules su-3.2# ipfw show | grep pipe 08380 1514852 125523804 pipe 1 tcp from any to any dst-port 80 su-3.2# ipfw pipe 1 show 00001: 2.000 Mbit/s 0 ms 50 sl. 1 queues (1 buckets) droptail mask: 0x00 0x00000000/0x0000 - 0x00000000/0x0000 BKT Prot ___Source IP/port____ ____Dest. IP/port____ Tot_pkt/bytes Pkt/Byte Drp 0 tcp 64.237.55.83/60598 72.21.81.133/80 6520267 1204533020 0 0 1216 su-3.2# first of all why when I run ipfw pipe 1 show i get same source and destination ip, that doesnt seem like ever change yet total packets/bytes increasing and most important question, after donig all that I'm looking at my MRTG stats and I see i'm very well over 2Mbit/s limit. what am I doing wrong? here is config file flush pipe flush pipe 1 config bw 2Mbit/s add 100 allow ip from any to any via lo0 add 200 deny ip from any to 127.0.0.0/8 add 300 deny ip from 127.0.0.0/8 to any add 8380 pipe 1 tcp from any to any src-port www uid daemon add 8380 pipe 1 tcp from any to any dst-port www uid daemon add 65000 pass all from any to any

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• How do I pipe a list of numbers straight from the shell into a command?

  - by learnvst

  How do I pipe a list of numbers straight from the shell into a command? For exampe something like this [1,2,3,4] | sort would give 1 2 3 4 EDIT: In response to the answers kindly posted so far . . . I ask this, because I want to quickly test and debug a console application that takes many numbers as it input without having to type lots of individual values followed by carriage returns. I'd like to just type in the 'one liner' and hit the up arrow now and then to replay the command. Ideally, I'd like to do this without using a text file containing the values (which would obviously be the most simple way to do this.)

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• Properly using subprocess.PIPE in python?

  - by Gordon Fontenot

  I'm trying to use subprocess.Popen to construct a sequence to grab the duration of a video file. I've been searching for 3 days, and can't find any reason online as to why this code isn't working, but it keeps giving me a blank result: import sys import os import subprocess def main(): the_file = "/Volumes/Footage/Acura/MDX/2001/Crash Test/01 Acura MDX Front Crash.mov" ffmpeg = subprocess.Popen(['/opt/local/bin/ffmpeg', '-i', the_file], stdout = subprocess.PIPE, ) grep = subprocess.Popen(['grep', 'Duration'], stdin = subprocess.PIPE, stdout = subprocess.PIPE, ) cut = subprocess.Popen(['cut', '-d', ' ', '-f', '4'], stdin = subprocess.PIPE, stdout = subprocess.PIPE, ) sed = subprocess.Popen(['sed', 's/,//'], stdin = subprocess.PIPE, stdout = subprocess.PIPE, ) duration = sed.communicate() print duration if __name__ == '__main__': main()

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• Bash script 'while read' loop causes 'broken pipe' error when run with GNU Parallel

  - by Joe White

  According to the GNU Parallel mailing list this is not a GNU Parallel-specific problem. They suggested that I post my problem here. The error I'm getting is a "broken pipe" error, but I feel I should first explain the context of my problem and what causes this error. It happens when trying to use any bash script containing a 'while read' loop in GNU Parallel. I have a basic bash script like this: #!/bin/bash # linkcheck.sh while read domain do host "$domain" done Assume that I want to pipe in a large list (250mb say). cat urllist | ./linkcheck.sh Running host command on 250mb worth of URLs is rather slow. To speed things up I want to break up the input into chunks before piping it and then run multiple jobs in parallel. GNU Parallel is capable of doing this. cat urllist | parallel --pipe -j0 parallel ./linkcheck.sh {} {} is substituted by the contents of urllist line-by-line. Assume that my systems default setup is capable of running 500ish jobs per instance of parallel. To get round this limitation we can parallelize Parallel itself: cat urllist | parallel -j10 --pipe parallel -j0 ./linkcheck.sh {} This will run 5000'ish jobs. It will also, sadly, cause the error "broken pipe" (bash FAQ). Yet the script starts to work if I remove the while read loop and take input directly from whatever is fed into {} e.g., #!/bin/bash # linkchecker.sh domain="$1" host "$1" Why will it not work with a while read loop? Is it safe to just turn off the SIGPIPE signal to stop the "broken pipe" message, or will that have side effects such as data corruption? Thanks for reading.

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• How can I both pipe and display output in Windows' command line?

  - by Bob

  I have a process I need to run within a batch file. This process produces some output. I need to both display this output to the screen and send (pipe) it to another program. The bash method uses tee: echo 'ee' | tee /dev/tty | foo Is there an equivalent for Windows? I am happy to use PowerShell if necessary. There are tee ports for Windows, but there does not appear to be an equivalent for /dev/tty, which complicates matters. The specific use-case here: I have a program (launch4j) that I need to run, displaying output to the user. At the same time, I need to be able to detect success or failure in the script. Unfortunately, this program does not set an exit code, and I cannot force it to do so. My current workaround involves piping to find, to search the output (launch4j config.xml | find "Successfully created") - however, that swallows the output I need to display. Therefore, I need some way to both display to the screen and send the ouput to a command - and this command should be able to set ERRORLEVEL (it cannot run asynchronously).

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• C check before writing to closed pipe

  - by Gary

  Is there an easy way to check if a pipe is closed before writing to it in C? I have a child and parent process, and the parent has a pipe to write to the child. However, if the child closes the pipe and the parent tries to read - I get a broken pipe error. So how can I check to make sure I can write to the pipe, so I can handle it as an error if I can't? Thanks!

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• write to fifo/pipe from shell, with timeout

  - by Tim

  I have a pair of shell programs that talk over a named pipe. The reader creates the pipe when it starts, and removes it when it exits. Sometimes, the writer will attempt to write to the pipe between the time that the reader stops reading and the time that it removes the pipe. reader: while condition; do read data <$PIPE; do_stuff; done writer: echo $data >>$PIPE reader: rm $PIPE when this happens, the writer will hang forever trying to open the pipe for writing. Is there a clean way to give it a timeout, so that it won't stay hung until killed manually? I know I can do #!/bin/sh # timed_write <timeout> <file> <args> # like "echo <args> >> <file>" with a timeout TIMEOUT=$1 shift; FILENAME=$1 shift; PID=$$ (X=0; # don't do "sleep $TIMEOUT", the "kill %1" doesn't kill the sleep while [ "$X" -lt "$TIMEOUT" ]; do sleep 1; X=$(expr $X + 1); done; kill $PID) & echo "$@" >>$FILENAME kill %1 but this is kind of icky. Is there a shell builtin or command to do this more cleanly (without breaking out the C compiler)?

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• I would like to pipe output of find into input list of scp, how?

  - by user13184

  I'm a novice linux user and I am trying to send a long list of files from one computer to another. The argument list is too long, so I am using find. I am having trouble setting up the expression, though. Can someone help? Here is what I would normally type for a short argument list. scp ./* phogan@computer/directory... Here's I think this might translate into with find. scp find . -name "*" phogan@computer/directory... Maybe I could use piping? Any suggestions would help. Thanks in advance.

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