Pipes or named pipes are a feature of the POSIX standard that allow separate processes to communicate with each other without having been designed explicitly to work together.

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How to pipe data over tcp from the command line?

I would like to pipe data from one machine in the command line to another machine over tcp. I guess I could write a socket server but this must already be implemented. For example I could use it to xz ...
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236 views

grep with colored output returns several empty lines

I have strange issue with grep (2.12-2, debian testing). In some situations when I do something like this: grep -rni '."spacer">.' . grep return me several empty lines: If I add --color=none ...
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1answer
158 views

Shell script detecting errors from command called by script

I am calling applications from my shell script, which performs a number of important steps in sequence, one step being below: for database in $( echo 'show databases;' | mysql ...
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81 views

Finding folders only

My harddrive is in a mess, so I decided to do a cleanup. As a part of this, I want to merge all folders containing music into one. What I want to do is, look for any *.mp3's and *.aac's on my drive ...
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111 views

Dynamic terminal title: show server load status at X second interval

When I have a bunch of terminals open in my WM it would be nice if terminal window titles reflected current user and host (easy) along with dynamic server load details, updated at some interval ...
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991 views

Pipe not working in cmd.exe on Windows 7

I have started seeing some very strange issues with the pipe command not working on Windows 7 64-bit on my machine. Commands like this: echo test | more used to work without a problem, but now ...
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243 views

Reading the same stdin with two commands in bash

I would like to pipe an output of to two separate commands <2,3> in bash. What is the best way of doing this? At the moment, I have following script: command source > output command2 output ...
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2answers
162 views

Windows Vista piping dir output into attrib command

I had a virus or something on my computer that set the attributes for all the folders in the root of my external drive to system and hidden, and created shortcuts to them. I am now trying to remove ...
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210 views

Alias defined in .bashrc not working after pipe

I'm stuck with the following problem. I've defined an alias in .bashrc (and .bash_profile): alias echo2="echo" This works well: $ echo2 "test" test However, if I try to use it after a redirect, ...
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1answer
809 views

How to redirect multiple bash commands to a variable AND screen?

I would like to capture a subshell's output in a variable and print it in the terminal screen simultaneously. Is it possible to do this by assigning the subshell to a variable and piping stdout and ...
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398 views

piping output from curl to rpm2cpio

I download alot of srpms to rummage through, I used to go through a long winded approach, root@server$ curl rpm -o file.rpm root@server$ rpm2cpio file.rpm | cpio -id but that leaves behind an ugly ...
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108 views

Transparent usage of temporary files as means of piping

As many of us are surely aware, it's always a good idea to make your program accept stdin input. Very many programs do allow that *nix environments. This lets us do cool things like piping echo "foo" ...
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226 views

cat-ing a file to a unix pipe causes Matlab to freeze

I've created a named pipe on Debian using mkfifo pipe.in. I want to write to this pipe from Matlab. To do this, I use the following matlab command: unix( 'cat <myfile> > pipe.in' ) ...
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212 views

How do I make a bash alias that outputs file names in a format I can pipe to vim?

When rebasing with git, I'm interested to open the files that have merge conflicts. I can do this with: vi `git diff --name-status --diff-filter=U | awk '{print $2}'` but if I alias that: alias ...
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0answers
465 views

Rendering HTML from a pipe

I would like to be able to generate HTML then pipe it to a program which will render it, something like this: for i in 1 2 3 do for j in a b c do echo "<table ...
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1answer
200 views

Redirect stdout to multiple programs

I'm doing some stream processing of some quite substantial files-- I was wondering if there was a way to split stdout in order to pipe to multiple programs. What I'd like to do is something like this: ...
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2answers
87 views

use pipe inside a find exec statement

I'm trying to find which jar contain a class, I wrote the below, which doesn't seem to work any ideas? find -type f -name "*.jar" -exec jar -tvf "{}" \| grep MyClass \; -ls
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2answers
598 views

Setting pipefail for a single piped command

I need to execute a number of piped shell commands from a non-BASH script (namely PHP script) like these: command1 | command2 | command3 so that, if command1 fails with a non-zero exit code, each ...
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5answers
279 views

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

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 ...
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2answers
93 views

Mutual piping on linux

I would like the output of A to be input for B and at the same time the output of B to be the input for A, is that possible? I tried the naïve thing: creating named pipes for A (pipeA) and B (pipeB) ...
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2answers
166 views

Why cat $(find /usr/portage -name *.ebuild) | grep RESTRICT - works? And find | grep - not?

Why I can't grep find? Only helps grepping cat of find. As I see program grep could see some context in which every command runs. But it's counterintuitive for a newbie like me. When given with ...
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1answer
157 views

Linux: access mounted volumes as normal folders/files

I have a closed source software (client) running on a Linux machine (Debian) to deliver files to a backup machine. This works fine except this client software does not access the mounted volumes ...
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298 views

Linux output redirection not working with awk

I'm trying to write a nice csv-file based on some output from top. I reformat the output with awk like this: top -b | nawk '/Cpu/ || /Tasks/ { if($1 ~ /Cpu/) { printf "%s,",$3 } else { printf "\n" } ...
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1answer
67 views

.cmd script output only goes to pipe occasionally

I'm having a problem with a .cmd script only occasionally passing it's output through a pipe. The script is auto generated by npm and it runs jshint using node. Here's the script: :: Created by npm, ...
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521 views

Piping bash output to perl script's arguments

I have the following bash command: find repo -name '*.c' What I want to do is use the files returned as arguments to my perl script, so that it's equivalent to running: perl ./myscript file1.c ...
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83 views

Launch only the command if the previous one worked inside SSH, shell

I've got a SHELL script which is using a pipe to separate my two commands: ssh -oBatchMode=yes user@hostname "mysql -u yop -pyop -c yop | echo test" The problem is even if my connection to MySQL ...
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2answers
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How do I unzip a compressed file as it's downloading?

I'm downloading a large file that's not an archive, and I want to combine the tasks of downloading and decompressing. How can I do them simultaneously?
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With regards to piping commands, what are the greater than (>) and less than (<) symbols called?

On linux at least, and I think windows/dos shell too you can use > to "pipe" output into a file. Something like: cat myfile.txt > mightAsWellCP.txt What is that piece of syntax sugar called? ...
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1answer
553 views

Unix bidirectional pipe on commandline

I've been able to use this linux command to connect Netcat to a serial port: nc -l 80 <> /dev/ttyS0 I would like to be able to log this transaction. My backup plan is to use Wireshark to ...
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2answers
292 views

How can I run several parallel shell jobs and monitor all of them at once?

I have a large number of large files (hundreds of files, hundreds of MB each) which I need to pipe through a number of programs to filter and convert them. I'm taking advantage of multiple CPU cores ...
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2answers
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pipe: too many files open renders entire OS completely useless

I'm running Ubuntu 12.04, and I am having a major problem. Two separate times today, one of my open gnome-terminal sessions locked up and printed the error pipe: too many open files I realize ...
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380 views

Transcode moviefile to h264/aac with ffmpeg for video and neroacenc for audio

I'm on Mac OS 10.8.1, with ffmpeg-devel installed as a macport. I can run NeroAacEnc(win32) via Wine. I can transcode a movie into h264/aac using a simple ffmpeg command: ffmpeg -i INPUT.MP4 -vcodec ...
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597 views

count files in a list of directories

I have file with a list of directories that I would like to know how many files are in each directory. .../images/idsuffix/userids/ This will give me the count of files and directories for ...
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1answer
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What are reasons for local Windows named-pipes to fail?

I've been working hard on this one all day and I'm stuck. This morning our asian collegues called me because a SolidWorks addin for our product data management system could not communicate with the ...
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3answers
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Can I use pipe output as a shell script argument?

Suppose I have a bash shell script called Myscript.sh that need on argument as input. But I want the content of the text file called text.txt to be that argument. I have tried this but it does not ...
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1answer
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How to connect to Ubuntu using Serial Port?

I am using VMware and I want to connect to Ubuntu VMs via serial port. I am connecting both using pipe as referred in this website https://www.vmware.com/support/ws3/doc/ws32_devices3.html How do I ...
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2answers
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Silence curl with >/dev/null 2>&1 when it's piped

So I have a curl that is piped to a grep and a sed. Where would I apply the >/dev/null 2>&1 ? curl www.site.com | grep stuff | sed "other stuff" At the very end or after the curl?
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1answer
368 views

Locked out of host after reaching some ulimit

So, I have a sudoer account in a remote host, in which I create a process with thousands of threads and sockets. The thing is, if I create too many threads/sockets (not sure which one, it might even ...
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1answer
180 views

Do people use dbus, pipes or ports usually for interprocess communication? [closed]

It's hard to find dbus libraries for the programming languages I've been using though the idea looks neat. Sockets are the most supported way but it also eats one of my computers ports and then I also ...
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2answers
382 views

Bash: Concatenating TAR balls

Is it valid to do this: { tar -c dir1 tar -c dir2 } | cat > file.tar Is the resulting file.tar a valid tar ball? If not, how can I concatenate tar balls on the fly?
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1answer
171 views

Pipe multiple commands to single grep

I'd like pipe the output of multiple commands to a single grep. Example: I'd like to combine these two lines: smartctl -A /dev/sda | grep -e Reallocated_Event_Count -e Current_Pending_Sector ...
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1answer
83 views

Why Does Issuing One lsof Launches Two Processes?

I'm on current OS X 10.7. Sometimes I want to check which application locks a certain file. I do that by lsof | grep $FILENAME I noticed that running this command invokes two instances of lsof. Why ...
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2answers
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In windows, can I redirect stdout to a (named) pipe in command line?

Is there a way to redirect the standard output of a process in Win32 console to a named pipe? Named pipes are built in to Windows and while they would be an useful concept, I've never seen them used ...
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2answers
338 views

How can I retain grep's match highlighting when piping find into grep?

If I run grep foo bar.txt, grep highlights each occurrence of "foo" in bar.txt. But sometimes I want to use find to determine which files grep searches. So I do something like this: find . -iname ...
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1answer
937 views

multiple png images over a single pipe to ffmpeg (no file writes to disk!)

I have a program that generates a script for gnuplot, which in turn generates a lot of png images and send it to stdout. I want to pipe these images to ffmpeg without writing them to the disk. This is ...
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4answers
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How to get both PIPESTATUS and output in bash script

I'm trying to get last modification date of a file with this command TM_LOCAL=`ls -l --time-style=long-iso ~/.vimrc | awk '{ print $6" "$7 }'` TM_LOCAL has value like "2012-05-16 23:18" after ...
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2answers
980 views

What is the magic separator between filenames in ls output?

The output of ls (with no arguments) appears to separate filenames with linebreaks. Evidence: ls | grep foo works as expected, with grep treating each filename as a separate line of input. ls > ...
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1answer
525 views

How to open the stdout with Notepad++?

On OSX TextMate have the alias mate which you can use with the pipe to open other program's stdout. How can I achieve the same effect in Windows 7 with Notepad++? Ex.: git diff master|edit
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896 views

How can I clear the contents of every file in a subdirectory without changing ownership / permissions?

I can find the list of files using something like: find /path/to/files -type f And I can clear the contents of a single file with any of: > filename echo -n > filename cat /dev/null > ...
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1answer
442 views

How to pipe output of tail -F on OS X?

I've recently moved from Ubuntu to OS X and I'm finding that the 'tail' command behaves differently. On Ubuntu I could run tail -f xyzzy.log | espeak (To have the computer read me what's happening ...