Chains the standard streams of a series of commands

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1answer
54 views

Best way to determine piped command to shell script?

Given tree /some/directory | print.sh Is there any way for print.sh to know that "tree -f /some/directory" was called, without trying to parse pid processes?
4
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1answer
39 views

Does pipe's link target exist somewhere in the filesystem?

I'm talking about this: $ readlink <(echo test) pipe:[80076194] Is pipe:[80076194] a path to the target or just indication that the file descriptor is connected to the pipe and doesn't exist in ...
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3answers
8 views

how to pipe the output of cut to the foreach command?

I have the cut command I want that grabs the first word in each line of a file. I then want to put each word from the cut command into a foreach. I then want to do a grep command inside the body of ...
0
votes
1answer
48 views

Pipe doesn't read my forked script [closed]

I have a problem. I modified a script called 'packer' a AUR-helper for Arch Linux. The problem coming when I apply my pipe, with a progress bar, doesn't show all info as I need. This is my forked ...
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2answers
33 views

Output of one command is piped to another one; how to close both?

I call Qt Assistant like suggested on stackoverflow: nc -lkU ~/.assistantfifo | assistant -enableRemoteControl & Qt Assistant window is opened, and if I call jobs, it returns: [1] + running ...
1
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1answer
31 views

Pipe chain with devices

As far as I know, you can have the ability to make pipes between applications, such as this one: $ step1 < input_file | step2 | step3 > result_file And you can access devices such as ...
0
votes
2answers
46 views

bash function output to pipe [closed]

I made a bash function to beautify svn output, this function show logs one line per commit, it is great! I like it, but if I use it with pipe it does not work. You can find it on github svn-beautify ...
4
votes
3answers
86 views

How to read user input in pipe?

Let's assume I have a file named confirmation.sh with the following content: #!/bin/bash echo -n "Are you sure [Y/n]? " read line case "$line" in n|N) echo "smth" ;; y|Y) echo "smth" ...
2
votes
2answers
171 views

filter and count with grep in a single pass?

I am using grep at the end of a set of piped commands to filter some rows out of a file. Afterwards I will want to do some arithmetic based on the number of remaining rows. e.g. ...
6
votes
1answer
95 views

bash scripting - read tarball from stdin

I have a task I need to script that I feel should be stupidly simple, but I'm actually having a rather tough time. I have a short bash script that takes a specific type of application in tarball form ...
5
votes
1answer
101 views

Loop through binary data chunks from stdin in Bash

I'm looking for something like while IFS= read -r -n $length str; do ... done but for binary data. Is it possible to do this using dd or other tools? Is there some technique to make these tools able ...
5
votes
4answers
143 views

Can a program next in a pipeline see the exit code of the previous program?

I would like to make a pipeline of Bash scripts like this prog1 | prog2 such that prog2 can see the exit code of prog1 and act differently based on that information. Is this possible?
4
votes
5answers
98 views

Semi-asynchronous pipe

Assume I have the following pipe: a | b | c | d How to wait for completion of c (or b) in sh or bash? This means that script d can start any time (and does not need to be waited for) but requires ...
4
votes
1answer
136 views

Why do piping and redirection work differently with here documents?

Combining a redirect with a here document seems logical enough: $ bash > foo <<EOF echo Hello EOF $ less foo Hello But with a pipe it behaves differently: $ bash | tee foo <<EOF ...
3
votes
2answers
50 views

Pipe / direct image / video output to foreign server

I am working on a Project that involves taking the output from a Webcam which is in either jpg or h.264 format, and outputting it to a foreign server (HTTP / FTP would work, I am open minded). What is ...
9
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2answers
182 views

How can I redirect `time` output and command output to the same pipe?

Suppose I have a binary called foo. If I want to redirect the output of foo to some other process bar, I could write ./foo | bar. On the other hand, if I wanted to time foo, and redirect the output ...
0
votes
1answer
33 views

Piped search queries in vim or less

I would like to be able to search a log file for lines that being with ^2014-02-18 15:30:[0-9:,]* and have UserName:someguy much later in the same line. I am sure I could do a regex to include any ...
3
votes
5answers
336 views

Counting files in folder without wc

Why does the following scripts give a count of 0 instead of giving the count of files present in the directory? #!/bin/bash cd /root/Jamshed/script count=0 ls -lrt > all_files cat all_files | ...
1
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1answer
108 views

How can I pipe commands to any terminal?

I often use more than one terminal (or terminal emulator) at a time; and while in X I can copy-paste commands, besides not being very practical, it obviously does not work on the real TTY. The first ...
2
votes
2answers
128 views

How to compose bash functions using pipes?

I have few functions defined in this fashion: function f { read and process $1 ... echo $result } I want to compose them together so that invocation would look like f | g | h. What idiom ...
1
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3answers
52 views

How to use the pipe command to open a directory after find?

Is there a way to opend found directories (via find) all in one command? One of the things I tried to study several times and never been able to really get, is the effective use of pipe: is it maybe ...
4
votes
3answers
202 views

Please help explain this bash output redirection

This script was posted as answer to a Question. And I'm trying to work out what's going on. result=$( { { ssh host app-status >&3 3>&-; echo "$?" } | { until read ...
5
votes
3answers
158 views

How to modify output in bash command pipeline

For example, I got from some command some lines $ some-command John Bob Lucy Now I'd like to add chaining command, that modifies output. $ some-command | other-command Hi John Bye Hi Bob Bye Hi ...
3
votes
2answers
72 views

Repeated commands in a bash pipeline

Sometimes commands repeat in pipeline command. For example (just to illustrate): $ grep -lF 'pattern' ./foo/**/*.bar | xargs dirname | xargs dirname Is there a way to shorten chaining command? For ...
3
votes
4answers
74 views

Pipe all input and output of terminal to file

I do not know if this is even possible or not, but in an attempt to keep track of many changes I am about to make to my system I want to track all input I type and all output from a terminal I'm ...
1
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2answers
337 views

Why does this ssh command not work? (cat ./file | ssh <user@host> “cat | sudo -t -t 'cat > /root/location/file'”)

I'm trying to do the following but it's not quite right. cat ~/Desktop/blah.png | ssh -t -t trusktr@50.116.4.56 "cat | sudo -i 'cat | /path/to/blah.png'" I have my public ssh key in the ...
3
votes
1answer
58 views

How can the order of execution in the shell as it relates to redirection be upset about 1 time out of a 1000 on my system? [duplicate]

Considering this Q&A about the order of execution in the shell as it relates to redirection, and despite the fact that if a file doesn't exist it gets created first so that cat example.txt | shuf ...
0
votes
4answers
132 views

Why does the command shuf file > file leave an empty file?

I know this is sort of a duplicate of another question (Why this sort command gives me an empty file?) but I wanted to expand on the question in response to the answers given. The command shuf ...
0
votes
2answers
26 views

How can I use tee to print the input stream?

I have a pipe line that looks like this: cat myfile | awk '$3 > 0 { print $1, $2 * $3 }' | tee >(printf) | perl myscript.pl I would like to print the input to my Perl script using tee. How ...
4
votes
1answer
63 views

Shell one-liner for adding a line in the middle of a pipe

I write a script which sends the input file to CPP, then to grep, then to a certain program: cpp $1 | grep -v "#" | theprogram But, "theprogram" requires the input to start with a certain constant ...
0
votes
0answers
36 views

Postfix mail how to debug transmission to mail handling agent

I have a postfix server running on Ubuntu (and Debian previously). The server is configured to read users and groups from an OpenLDAP server and delivers mail first the spam filter and then to a ...
3
votes
2answers
110 views

grep string from contents of file command then delete file

I have a peculiar problem I need help with. I have a large batch of .docx files where a certain number of them are junk. I know how to identify these files from the file command, as they contain the ...
2
votes
1answer
50 views

Piping periodic data between Python scripts

How to receive data from the environment e.g. bash I am trying to launch two Python scripts in bash and pipe stdout from one of them to stdin of the other. The first script outputs a single ...
2
votes
3answers
110 views

Preserving color output with cut

Using bash interactively I am trying to use cut to prevent the lines from going longer than my terminal width. But when using a command with colorized output all the color gets removed by cut. For ...
1
vote
1answer
37 views

Memory-efficient utility to return N first sorted values

I would like to implement a very popular MapReduce example using only existing programs operating in a UNIX way. The problem is to find N most frequent values in an enormous amount of data. The ...
3
votes
1answer
100 views

Why does grep change the length of output lines?

I often use dpkg or aptitude combined with grep when I want to list certain packages available or installed on my system, but I noticed that when I add | grep, the output lines look a little bit ...
1
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5answers
140 views

Pass the output of previous command to next as an argument

I've a command that outputs data to stdout (command1 -p=aaa -v=bbb -i=4). The output line can have the following value: rate (10%) - name: value - 10Kbps I want to grep that output in order to ...
2
votes
2answers
34 views

Piping to the command substitution of a string containing pipes

This works— $ x='grep a' $ echo ab | $x ab This doesn't— $ x='grep a | grep b' $ echo ab | $x grep: |: No such file or directory grep: grep: No such file or directory grep: b: No such file or ...
1
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2answers
170 views

Help me understand this echo/spawn/send/expect construct

Here is a line from a bash script I am trying to understand: echo "spawn myscript.sh arg1 arg2; expect \"Please enter your value: \"; send \"myval\r\"; expect eof" | expect I think I understand the ...
4
votes
3answers
89 views

processing command output line by line, without mixing standard input

So, I have a problem very similar to Bash: How to read one line at a time from output of a command?, I am doing: while read path; do mplayer $path; done < <(find-me-random-mp3s) or ...
1
vote
1answer
24 views

Mysql import the most recent file from a directory

I have a directory with daily backups of my entire MySQL database. I want to import the most recent backup into the database. I know to import a backup I need to use mysql -u root -ppasswordhere ...
3
votes
1answer
118 views

How does the piping in this command ultimately achieve to kill the process?

I have seen the following line in a bash script for killing a process(in this case started with the command loadgen): ps xww | grep -i "loadgen" | grep "PATTERNMATCH_FACT.xml" | cut -c1-5 | xargs -i ...
4
votes
2answers
111 views

Is there any way to use xargs across a pipe?

I'm trying to automatically convert flac files moved to a folder into mp3 in another folder. My current line of code is this: inotifywait -m -r -q -e moved_to --format "'%w%f'" ~/test | xargs -I x ...
5
votes
1answer
108 views

Replace CD number in MP3 ID3 tag

I have a library of MP3 files where in some files the "CD number" tag (TPOS) contains "CDx" values, e.g. "CD1" or "CD2". The ID3 spec says that TPOS values shall be numerical strings. Processing these ...
16
votes
9answers
831 views

Grep lines but let the first line through [duplicate]

Consider the following output from df. Filesystem Size Used Avail Use% Mounted on /dev/sda1 23G 6.1G 16G 29% / udev 10M 0 10M 0% /dev tmpfs 397M 420K ...
2
votes
3answers
82 views

The processing order and printing of files with find

This simple BASH script collects msgstrs in a PHP project: #!/bin/sh TARGET=/path/to/project LPATH=locale/cy_GB/LC_MESSAGES POFILE=messages.po mkdir -p $LPATH touch $TARGET/$LPATH/$POFILE cd $TARGET ...
24
votes
3answers
482 views

Multicolored Grep

I'm trying to get each grep command to highlight it's results in a different color. I can do it manually with a line like this: ls -l GREP_COLORS='mt=01;32' grep c | GREP_COLORS='mt=01;31' grep o | ...
13
votes
2answers
386 views

Use of ^ as a shell metacharacter

I wrote a small script today which contained grep -q ^local0 /etc/syslog.conf During review, a coworker suggested that ^local0 be quoted because ^ means "pipe" in the Bourne shell. Surprised by ...
1
vote
3answers
60 views

Print a message from the left-hand side of a pipe

I want to use a variable from the main shell in a sub shell. I did: export mysql_root_password="test" ( echo $mysql_root_password ) | dialog --gauge "Working hard..." 6 50 But it does not ...
4
votes
3answers
90 views

cycle through one command's output and use in another command [duplicate]

How can I use the output of one command - line-by-line - into another command? I know how to do this with the | pipe symbol, but this uses the entire output in one command. I would like to go line by ...