A Unix pipe connects file descriptors of two processes. A pipe is created with the POSIX pipe() function declared in . Shells provide pipe creation between processes using "|".

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32 views

operate on different sections of stdin without intermediate file

Is there a simple way to do this with redirection or pipes without creating FILE1? I want to apply process2 to the body of the output of process1, without touching the first and last few lines. ...
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2answers
63 views

Using a file as an input to a script

Say I want to use the name of a file as input, and process it with a pre-made script in a certain directory. How do I do it? fileName < /folder1/scriptName is this the right format?
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2answers
57 views

piping with grep

I want to search "C" in the grades column inside the file "input.csv": roll,name,total,rank,grade 001,A B,78,23,C 003,F YZ,100,1,* and what I'm trying is: cut -d"," -f4 input.csv | grep "C" ...
3
votes
1answer
727 views

pipe mplayer output to other tool

I'm trying to play an online live stream via mplayer and pipe the audio from that stream to another tool. Playing the stream works fine: mplayer http://user:pass@192.168.0.1:8080/stream.flv But ...
2
votes
1answer
98 views

pipe speed benchmark with machine readable output

I'm looking for a tool similar to pv which is producing machine readable output. And i cant believe that nobody did it bevore... I looked at the manpages of pv, pipemeter, dd and cpipe but all these ...
2
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1answer
152 views

Is there a system call to bind a file descriptor directly into another?

A read() & write() loop would probably be as good as what I'm looking for, but nevertheless is anything like that around or is it impossible because of an obstacle I didn't envisage ? I'm curious
2
votes
1answer
627 views

How to redirect and use the framebuffer?

I need to work on the framebuffer to record what is being rendered. Now, I figure out how to convert the framebuffer in an image, I'm currently unable to obtain a constant stream of data from the fb ...
1
vote
1answer
62 views

How to get `yum list` output to stay on one line when getting output via remote ssh command?

When I SSH to a machine with ssh machine and run yum list it outputs everything that's installed as expected, and importantly every item is on one line like so: xz-devel.i386 ...
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1answer
99 views

`docker logs foo | less` isn't searchable or scrollable but `docker logs foo 2>&1 | less` is

Using either one gives readable text. But only with the stderr redirect can one scroll or type /somepattern and get matches. Without it searching gives "Nothing to search (press RETURN)" and a ...
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1answer
124 views

Grep -v filter not working

I want to filter grep results by using grep -v option. But the output does not differ when using a particular pattern. contents of log.log: ERROR error EXCEPTION exception <STATUS>ERROR</...
0
votes
1answer
58 views

Fetch second and fourth column from a file

Problem Statement I am not able to get the values in second and fourth column. Tried grep -i "AUGC\|AACN\|AACY" output.csv | cut -d ',' 2,4 DATA success,1234,["madhu",{'first',[{'last',18}]},"I0"...
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votes
1answer
169 views

Combine the output of while loop into tar

I'm trying to create a script that mysqldumps all my databases, creating an individual .sql file for each database and combines the output into backup-DATE.tar.gz. I've gotten as far as being able to ...
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1answer
415 views

Redirect a directory as input to a script and output to a file

I want to use a directory name as a parameter for a pre-made script. Then the output goes into a newly made file in the home directory. It involves pipe/redirection. How do I do that? read dir $dir &...
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votes
1answer
71 views

How to do inter process communication using single bidirectional pipe in linux?

How do 2 processes communicate by using single bidirectional pipe, such that both the ends of the pipe could read and write. I have an assignment to do, kindly help me with this.
5
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0answers
54 views

Piping the output of a bash script after redirecting stderr

because of the way my hoster does things I have to use a system for services. This service has a run file which it executes and pipes into a second run file. But I use a (given) python package that ...
3
votes
0answers
61 views

two piped commands, each needs to read password from stdin

Is there a way to sensibly do this: scp user@host:/path/to/file /dev/tty | openssl [options] | less without creating a file, and without having to supply either password directly in arguments? The ...
3
votes
0answers
245 views

Scripted write-then-read from Unix domain socket using socat

I have a simple server listening on a Unix domain socket (on a CentOS box in case that's important). When I send the command "DATE" to the socket it writes back a welcome message and then "APRIL 15 ...
2
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0answers
130 views

Understanding inotifywait, pipes and buffers

I want to monitor every file change in a directory with inotifywait. inotifywait shall write to a FIFO buffer, which then can be read, leisurely. While experimenting with relatively huge amounts of ...
2
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0answers
47 views

How many ways are there to convert and pass stdin as command parameter?

I am new to Linux shell. I know that xargs can be used to accept stdin from a pipe and pass it to another command as parameter. Are there other ways to do so? Is there a list I can refer to? A non-...
2
votes
0answers
263 views

Pipe a .BIN file into XModem transfer

I need to send a .bin file to a modem via XModem transfer for firmware upgrading. If the modem is connected to a local computer, the command would be the following: sz -X -k -b -vvv - ...
2
votes
0answers
57 views

Close All Piped Commands if one close

I'm running at least 3 commands (with progs) using pipes. For example program1 bla bla | program2 blabla | program3 bla bla Is possible to close all programX PIDS automatically if at least one ...
2
votes
0answers
564 views

avconv/ffmpeg output through /dev/ttyAMA0

I tried to pipe streaming video from video4linux2 webcam connected to a Raspberry Pi through /dev/ttyAMA0 to a computer using an Arduino as a intermediary. First of all, is it possible? Because I was ...
2
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0answers
475 views

Why does this pipeline get SIGTTIN?

When I run the command for i in *.log; do cat "$i" | sort; done | more, the pipeline gets a SIGTTIN signal and is stopped. bash$ for i in *.log; do cat "$i" | sort; done | more ### (one screenful of ...
2
votes
0answers
210 views

Automatically start named pipe reader on startup?

I'm trying to run a script with root access from PHP. I can't do that because Apache's user, www-data, don't have root access because of security reasons. To fix that, I was advised to use a named ...
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0answers
22 views

strace for troubleshooting inter process communication

I have output captured by following command: strace -f -e trace=process,socketpair,open,close,dup,dup2,read,write -o rsync.log rsync -avcz --progress src/ dst/ it is a bit long so I've uploaded it ...
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0answers
33 views

When was pipelining introduced?

I understand early versions of Unix were licenced from AT&T to Universities and ran on PDP computers. I read in Tanenbaum's book (operating systems) that the first versions of Unix were only a ...
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0answers
7 views

Track amount of data application and a device file are exchanging

Is it possible to track how much data is going into a device file and an application as a third person? Background A web server is communicating with a device /dev/ttyACM0. The server offers a HTTP ...
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0answers
21 views

Pipe output of process that's already running

I've got a process that spews out a lot of output, and it's going to be running for the next hour. I forgot to pipe its output through my awk script before I started running it. Now my terminal is ...
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vote
0answers
188 views

Half-close netcat connection

How can I have a netcat connection terminate the sending half of a TCP connection if its input reaches EOF? I have a (non-standard) TCP service which reads all its input (i.e. until the client sends ...
1
vote
0answers
175 views

csh: redirecting output from foreach

In csh: How do I redirect the output from a foreach-loop to a pipe? This works but uses a temp file: set tmpfile=/tmp/file ...
1
vote
0answers
68 views

UDEV-rule:Open new gnome-terminal window on usb-plugin AND activate it for stdin/stdout/stderr?

My attempt is this: If a certain USB-device is plugged in, I want to open a gnome-terminal window in my desktop-environment. This newly opened window must be able to be interactive, this means, the ...
1
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0answers
29 views

Pipe gzip output to Bluetooth transfer?

How do I pipe gzip output to Bluetooth transfer? I am able to send send file over Bluetooth using this command: bluetooth-sendto --device=12:23:35:96:45:45 file.tar However, piping gzip didn't ...
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0answers
150 views

Correct/Efficient/Reliable way to import log file entries to a MySQL database?

I'd like to be able to query our server access log files to identify abuse patterns. Log files really aren't very queryable, and it would be fairly easy to do what I wanted if each hit was a row in a ...
1
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0answers
150 views

Verbose output in logfile and simple output on screen?

Let's say I have the following script: script.sh and i want the verbose output in a logfile and simple output on screen. Logfile should contain the csh -v script.sh output, and on the screen should ...
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0answers
28 views

AH00493: SIGUSR1 received. Doing graceful restart

My Apache is restarting a few times a week. I use cPanel and I have "piped logging" enabled (which should prevent restarts). However, how can I know what is sending SIGUSR1 signals to Apache at ...
0
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0answers
40 views

What does the “pipe” command do in mailx?

When using the mailx command line utility, there is a command called pipe listed in the man page (although not visible when using the help command). What does this command do? I want to be able to ...
0
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0answers
49 views

How do I connect to Hyper-V VM's serial port from Linux?

I run Linux as a virtual machine on MS Hyper-V hypervisor from Windows Server (2008 R2 and 2012 R2, 2016 would be nice as well) and I want to read output from the VM's serial port (one-way ...
0
votes
0answers
53 views

Is a pipeline made of simple commands?

From Bash Reference Manual A pipeline is a sequence of simple commands separated by one of the control operators | or |&. From POSIX 2013 A pipeline is a sequence of one or more commands ...
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0answers
20 views

Piped sequence - printing

I need to write a piped sequence of commands that prints out a list of all sub directories of a current directory. In order to get all sub directories of a current directory I use: ls -D Since I am ...