Chains the standard streams of a series of commands

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3
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3answers
149 views

Piping a script with “read” to bash

I need to run a script by piping it through bash with wget(rather than running it directly with bash). $ wget -O - http://example.com/my-script.sh | bash It's not working because my script has read ...
1
vote
3answers
44 views

Tailing log files in two different hosts

I'm trying to tail two log files in different hosts and use the merged output as a single one. ssh HOST_1 "tail -f MY_LOG_FILE" I'm also using mkfifo to create a named pipe. mkfifo MY_PIPE The ...
3
votes
2answers
66 views

How to use tee to capture STDOUT from a code block to a filename defined within the block?

I want to send STDOUT for a script block to a file which name is defined by a variable within the block. However, when I use tee, it seems the variable outside the block doesn't exist anymore. Without ...
1
vote
1answer
41 views

Output Redirection

I am using the tee command to output the compilation errors of a program into a file along with the terminal. gcc hello.c | tee file.txt This is the command I have used. The compilation errors are ...
0
votes
1answer
22 views

exit status and no output

I have a command such that bar > /dev/null and I want to know the exit status of bar. I read some posts su about ${PIPESTATUS[0]} but this works when one pipes the output via | and I can't make ...
2
votes
2answers
49 views

What exactly is the difference between pipes and streams?

I read about pipes and streams and I’m still confused on how it’s implemented. A program is started and it reads data from “standard input” stream (stdin), which is where the keyboard sends data to. ...
0
votes
0answers
30 views

Pipe to `ls` Not Working as Expected [duplicate]

When I issue: [dave@dhost ~]$ which tar | ls -l I get the output of ls -l of the pwd. I expected to get: -rwxr-xr-x. 1 root root 395472 Feb 21 2013 /bin/tar Why doesn't the pipe work as I ...
4
votes
3answers
144 views

Using | pipe character from a $variable makes it treat as just another argument in bash; how to escape it?

I have a bash script like this export pipedargument="| sort -n" ls $pipedargument But it gives the error ls: |: No such file or directory ls: sort: No such file or directory It seems to be ...
2
votes
2answers
82 views

Feed source command with a pipe

Previously I used source command like this: source file_name But what I'm trying to do is this: echo something | source Which doesn't work.
2
votes
3answers
39 views

Pipe files downloaded with wget into a function

I'm downloading a bunch of images with wget and I want to rm the files if they are empty with a function to which I can pass the file. My question is how do I pipe the images to a function like this: ...
1
vote
1answer
30 views

preserving colors when piping yaourt through sort

Can sort preserve piped in colors? I'm trying to modify yaourt -Qu | sort so I get color output. Tried googling this but I couldn't find a general way nor a special way to do this for sort.
0
votes
1answer
25 views

Why doesn't this tee with process substitution produce the 1st and chosen lines? [duplicate]

What I want is printing the output the first line ( table head ) of ps aux and the grep result. After search, I come up with following. ps aux | tee >(head -1 > /dev/tty) | grep mongo But I ...
1
vote
1answer
16 views

How do I make an alias to substitute single word in a piped command? [duplicate]

I use aliases a lot but right now only for use cases like alias i='sudo apt-get install -y'. I often would like to add an alias in the following form: alias cmd='echo [something] >> ...
3
votes
3answers
74 views

Redirecting stdout to terminal and file without using a pipe?

I have code, that goes something like this: #!/bin/bash VAR=0 func() { VAR=$((VAR+1)) echo 'Logging information.' } func 2>&1 | tee 'log.txt' echo "Should be 1: ${VAR}" When ...
3
votes
2answers
81 views

Am I hitting a race condition in bash?

I have a script which compares the output of a command with the output of the same command as it was ran previously, it works most of the time, but every now and then it doesn't work as expected. ...
2
votes
3answers
88 views

source /dev/stdin doesn't work as expected

Let's start with simple tests that work for me to check that source /dev/stdin can be used at all. # echo -ne 'echo a\necho b\n' | source /dev/stdin a b Now I would like to source an actual ...
4
votes
1answer
104 views

cmd2 `cmd1` vs cmd1 | xargs cmd2

I'm trying to find a file with find and then pass the found path to sqlite3. I'm only dropped into the sqlite> prompt if my command is of the form: sqlite3 `find . -type f -iname "*.db" | head ...
0
votes
1answer
19 views

Force ping to write before interrupt

I am trying to get ping to continuously write some times to a file. When I run $ ping 10 10.1.10.28 | perl -ne '/time=(\d+\.\d+)/ && print "$1\n"' It returns one number every several ...
6
votes
4answers
458 views

Back to back Pipes into a Command

Is there a way to pipe back to back values into a command? e.g. If I can command.pl and want to pipe in response, then y to confirm (because it doesn't have a way to auto confirm)? I've tried echo ...
0
votes
1answer
53 views

Using tee or pipe to log console output will cause my program not to start [duplicate]

I'm running hostapd on my raspberry PI to let it function as an accesspoint. It's working fine with the following command: sudo hostapd /etc/hostapd/hostapd.conf This will start hostapd and log all ...
2
votes
1answer
38 views

'Tar' the result of a 'find', preserving the directory structure

I want to tar all the *.txt file, that I get from the result of a find, that exist into a directory having a tree like this: Directory_name dir1 file1.pdf file1.txt dir2 file2.pdf ...
3
votes
1answer
55 views

Problem with getting interactive input in while read loop

I was doing something like the following minimal example: #! /bin/sh # $1 = file containing list of files to sync # $2 = source dir ; $3 = target dir cat "$1" | while read f do cp -i "$2"/"$f" ...
2
votes
2answers
119 views

How to read from a named pipe after the writer process exits?

I want to use named pipes as asynchrnonous task queues (JMS-like, perhaps). For example, suppose a client sends some data that I wish to insert into a database, but I want the client to disconnect ...
2
votes
1answer
39 views

Problems with find, xargs and egrep

I this is what I what I'm trying to end up with (except working) find ./ -mindepth 1 -type f -mtime +60 -print0 | xargs -0 egrep -vZ 'vvv|iii' What am I doing wrong? $ ll total 0 -rw-rw-r-- 1 ...
3
votes
2answers
87 views

Less resource hungry alternative for piping `cat` into gzip for huge files

I have some files of which some are very large (like several GB), which I need to concatenate to one big file and then zip it, so something like this: cat file1 file2 file3 file4 | gzip > ...
1
vote
2answers
178 views

awk - Group by and sum column values

I have command to list system process by memory usage: ps -A --sort -rss -o comm,pmem Which list a table like COMMAND %MEM firefox 28.2 chrome 5.4 compiz 4.8 ...
3
votes
2answers
90 views

How to read user input when using script in pipe

General problem I want to write a script that interacts with the user even though it is in the middle of a chain of pipes. Concrete example Concretely, it takes a file or stdin, displays lines ...
3
votes
2answers
153 views

Bash: cannot break out of piped “while read” loop; process substitution works

I intend to pipe the output of a program into a while read VAR loop and break when a pattern is found, but it doesn't. Proof of concept: inotifywait -qm -e create . | while read line; do echo $line; ...
1
vote
2answers
34 views

Capturing data from a Fluke 1620a via netcat

I am trying to pull temperature and humidity data from Fluke DewK 1620a thermo-hygrometers and write the temp/humidity readings to a log. I can connect to the device via netcat with a simple 'nc ...
2
votes
2answers
53 views

How to pipe a the output of find to another find invocation

Here's what I'm trying to do find . -maxdepth 1 -type d -print0 | xargs -0 -P4 find -name 'war' -type d I would like to create a list of directory names, null-terminated, and then pass this list to ...
1
vote
2answers
94 views

How does Bash pipe large amounts of data?

Let's say you want to cat the contents of a really big file, but want to view it a few bits at a time. Let's say one were to do the following: $ cat /dev/sda1 | less As a programmer of languages ...
1
vote
3answers
34 views

Command that passes its input through to output AND performs command?

I'm trying to use the quote program to make a little shell script that'll keep updating the stock prices every second. quote has to access the Internet and therefore has a small delay when it runs. I ...
1
vote
2answers
86 views

Combination of echo, pipe and cat

I have a file name called temp.csv in my script one of the intermediate step is echo "some info" > final.csv | cat temp.csv >> final.csv at times the file final.csv is created without ...
1
vote
1answer
53 views

Using find -exec and having trouble with redirecting standard error

I have an individual.sh script that pipes standard error to a grep command, like this: FOUND=$(tesseract "$i" out -psm 0 |& grep -ci 'Orientation in degrees: [^0]') If I run the script like ...
2
votes
1answer
32 views

Confused about piping commands from find to commandX?

I have a script, run.sh, that looks like this: #!/bin/bash FILES=$(find corpus/ -type f) for i in $FILES do ./individual.sh $i done It runs without problem. I want to do away with the run ...
1
vote
1answer
68 views

Pipes & redirection binding precedence with disjuncts, conjuncts etc?

I know of the relative binding precedence of operators ‘;’, ‘&’, ‘&&’, or ‘||’ http://www.gnu.org/software/bash/manual/bashref.html#Lists but when pipes come into the picture along with ...
1
vote
0answers
80 views

In adb logcat | grep, how to get the entire original line? [closed]

I am using grep on the Android Logcat to only watch the lines related to my application. My command line is like: adb logcat | grep 'MyAppName' But the results I get is not the original logcat ...
3
votes
1answer
47 views

How to find the file corresponding to a pipe opened by a process? [duplicate]

I created this script, which listens for characters received on a hardcoded pipe, and tries to eval those characters. I call my script loop_executor.sh This is all it contains: !/bin/bash while : do ...
1
vote
1answer
55 views

Redirect output to stdout and pipe to a binary

I have a nice PS1 line in my .bash_profile, and I want to copy it to another machine. So I want to view it AND copy it to my clipboard. I can't figure out how to string the commands to do this ...
2
votes
1answer
111 views

Advantages of using named pipes and sockets rather than temporary files

I have two cooperating programs. One program just writes its output to a file and the other one then reads from the file and spits the data out for the front end to work with. I have been reading ...
3
votes
2answers
165 views

How can a bash script write its standard output from within a pipeline? [duplicate]

I have a bash script that calls a function. The function, amongst other things, executes a pipeline that sinks its output. To simplify it, here is a contrived example: #!/bin/bash func() { ls "$@" ...
1
vote
2answers
64 views

Append a file, output to screen and redirect from stderr all at once, without tee

I'm running a time dd command in a shell script, and I'd like to output the results to a file, and print it out on the screen. The line that I'm currently running is: (time dd of=$dest_filepath ...
5
votes
2answers
307 views

Use bash's read builtin without a while loop

I'm used to bash's builtin read function in while loops, e.g.: echo "0 1 1 1 1 2 2 3" |\ while read A B; do echo $A + $B | bc; done I've been working on some make project, and ...
1
vote
1answer
64 views

Understanding grep and pipes in linux

I came across this post which explains my problem. Suppose there is a file called file.txt which contains "foo World". The answer posted by Tyler explains a lot however I am confused as to how cat ...
0
votes
2answers
483 views

How to redirect stdout & stdin to telnet? [closed]

I am working on embedded product running Linux. The device uses /dev/ttyO0 as console. On boot is automatically start a program with which uses input from /dev/ttyO0 (serial), and gives some ...
4
votes
3answers
95 views

Time required to do pipe output to head/tail [duplicate]

There are lots of txt files in a directory. If I do time wc -l *.txt | head it takes real 0m0.032s user 0m0.020s sys 0m0.008s If I do time wc -l *.txt | tail it takes real 0m0.156s ...
0
votes
4answers
98 views

grep for files and open the resultant matches

I'm trying to open all files based on some return values from grep in the command line. I know that I can use the -l option to only return filenames, but I would like to combine this somehow with ...
0
votes
1answer
84 views

Very basic H/W question using pipe and grep

I have two text files, F1a.txt and F1b.txt, with essentially the same data: the driver's surname and their nationality. For example: Hamilton GBR Alonso SPA I have concatenated these ...
-1
votes
1answer
76 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 ...
0
votes
2answers
37 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?