2
votes
2answers
52 views

Should I use piping or redirection for input to 'sort'

I want to do awk -F "," '{print $1 }' inputfile1.txt | sort -u > distinctOutput.txt Is this good performance-wise ? Or should I redirect / use a temp file since I think it is better to make sort ...
3
votes
4answers
168 views

Redirect and pipe output

rpm -qa > file | wc -l returns 0. What am I doing wrong? I think it is clear what my goal is, but it isn't working. Is this a job for xargs or tee?
1
vote
3answers
36 views

How can I pipe data over network or serial to the display of another linux machine?

I have a second monitor that I'd like to use for a text-based debugging log and/or console. I don't want to have it as part of my GUI / "desktop" / main system. I have this display connected to an ...
1
vote
1answer
63 views

Why doesn't this piped script work?

#!/bin/bash rm out mkfifo out nc -l 8080 < out | while read line do echo hello > out echo $line done If I browse to the IP of the machine this script is running on (using port ...
2
votes
1answer
494 views

bottomless tee?

I was just playing around in the terminal and I did this: printf 'some string\n' | { tee /dev/fd/3 | { : && sed 's/some/string/' } } 3>&0 I was really surprised when ...
4
votes
3answers
195 views

Environment variables are not set when my function is called in a pipeline

I have the following recursive function to set environment variables: function par_set { PAR=$1 VAL=$2 if [ "" != "$1" ] then export ${PAR}=${VAL} echo ${PAR}=${VAL} shift ...
1
vote
1answer
119 views

Send copy of a script's output to a file

Say I have a Zsh script and that I would like to let it print output to STDOUT, but also copy (dump) its output to a file in disk. Moreover, the script starts with the following option set -o xtrace ...
22
votes
1answer
562 views

How do I redirect command completion output?

On the command line, I can redirect or pipe output of a command to a file or another command using the > or | operator after the command. I have come across a less standard situation that I would ...
4
votes
1answer
209 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 ...
0
votes
1answer
48 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 ...
4
votes
3answers
665 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 ...
0
votes
4answers
318 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 ...
2
votes
2answers
94 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 ...
2
votes
2answers
165 views

turn off buffering for `hping` in OpenBSD

It would appear that the output from hping is fully buffered when piped to perl for further line-by-line processing, so piping hping to perl doesn't work. hping --icmp-ts example.ca | perl -ne 'if ...
1
vote
1answer
107 views

Pipe not picking up stdout

I am running a java program from a OS X 10.8 bash terminal, and are trying to rederect the output it is producing. However, when either running this throug a pipe, or rederecting it to a file, the ...
4
votes
3answers
533 views

Split stdin by lines

I want to invoke a command for every line of the standard input, much like xargs, but the line should be passed as standard input, not as a command-line argument: cat some-file.txt | <magic> | ...
2
votes
1answer
2k views

redirection to file issues with nohup and pipe

For the following command: ssh -t esolve@hostname 'sudo nohup bash -c "ls > log 2>&1 &"' I always got error information: nohup: ignoring input and appending output to ...
0
votes
2answers
493 views

Redirecting stdin with stdout to file

So I have a program that takes in user input and outputs text based on the input. EDIT2: I want to create a script that runs a C executable and the script feeds the C program input from a file and ...
4
votes
4answers
1k views

Getting stdin from a named pipe

What I am trying to do is run python in a terminal window and redirect it's stdin from a named pipe. Then I write to the named pipe in another terminal and have that command execute on python. ...
2
votes
1answer
116 views

Stderr of piped shell scripts isn't always displayed

I piped my own shell scripts for some testing and accidentally noticed something strange. Namely, the stderr of those piped processes isn't always displayed on the screen. I simplified the scripts ...
3
votes
4answers
2k views

How to pipe the stdout to a file if the current command is already being piped through gzip

So I have this command I need to run then disown: innobackupex-1.5.1 --user=root --password=**** --stream=tar ./ | gzip - > /data/myfile.tar.gz How do I pipe any output to a file? adding ...
2
votes
1answer
262 views

How to copy the output of pacman-color into a file and to display the output with the colors in the terminal

Originally I used pacman, not pacman-color and I copied the output into a file and I displayed the output in the terminal with the following command : pacman -Syu | tee file.log Unfortunately, it ...
2
votes
4answers
160 views

store and execute redirection/piped command in script

How do you store, and later execute, a command with redirection and and a pipe? (And is it the pipe, or the redirection, or both, that's causing my problem?) I tried to print the urxvt version in a ...
9
votes
2answers
2k views

echo vs <<<, or Useless Use of echo in Bash Award?

By now the Useless Use of cat Award is very well known, and there's also a mention of a Useless Use of echo (not relevant for this question). I'm wondering if there should be a "Useless Use of echo in ...
2
votes
3answers
2k views

Count running processes using wc and ps

I tried using ps r > log | wc log but this returns Ambiguous output redirect.. Can someone explain why and provide another solution?
1
vote
1answer
105 views

What is the difference between who > lp and who | lp?

Why does the who > lp creates a file but who | lp leads the output to program lp? What is the underlying principle behind these two simple commands? Can somebody explain it with an example?
1
vote
2answers
569 views

Print/Tee to console without passing output to pipe

Is there a way to print or tee one thing to the console and still pass something else through to the next pipe? Something like: echo dog | printOrWhatnot "PUTTING MY THING DOWN" | sed 's/dog/cat/g' | ...
24
votes
6answers
2k views

Why can't I redirect a path name output from one command to “cd”?

I am trying to get cd to accept a directory name redirected to it from another command. Neither of these methods work: $ echo $HOME | cd $ echo $HOME | xargs cd This does work: $ cd $(echo $HOME) ...
2
votes
2answers
3k views

What's the difference between STDIN and arguments passed to command?

I could use the either form to execute the cat method: cat file_name cat < file_name The result is the same Then I want to execute man in the format of STDIN man < file_name For the ...
0
votes
1answer
217 views

The “cp p2 &2 &” command makes Konsole to disappear, is it a bug?

The goal is start a background process that copies the data from the pipe p2 to the STDOUT as p2 is feed with data by some other process. I guess the command is incorrect. Nevertheless, the Konsole ...
5
votes
2answers
1k views

Behavior of stdin/stdout in conjunction with subshells and cd command

I have the following series of commands: cd / && ls | ( cd /tmp && cat >dumpfile) This series of commands does the following: it creates a file named /tmp/dumpfile. This file ...
96
votes
1answer
5k views

Bash: What does “>|” do?

I have just seen this written down; $ some-command >| /tmp/output.txt Vertical pipes are used in standard redirects "piping" the output of one command to another, is >| in fact completely ...
2
votes
1answer
105 views

pipe and log STDOUT at the same time

Some programs output very detailed data, for readability I use awk to filter them. ./output_many_things | awk '{print $1 "\t" $2}' But I don't want to miss anything. Could I redirect the complete ...
4
votes
1answer
274 views

command like wc but with tee behaviour

I want to backup a database using psql and COPY command. here is my script: psql "user=${USERNAME} host=${HOSTNAME} dbname=${DBNAME} password=${PASSWORD}" -c \ "COPY (SELECT * FROM tbl) ORDER BY id ...
6
votes
2answers
3k views

what is meant by connecting STDOUT and STDIN?

This is a newbie question. I'm reading a book, it says: Every process has at least three communication channels available to it: “standard input” (STDIN), “standard output” (STDOUT), and ...
11
votes
3answers
3k views

How can I pipe output to another process, but retain the error state of the first process? [duplicate]

Possible Duplicate: Get exit code of process that's piped to another I am using the following command line (in a makefile) to pipe the verbose error messages from my compiler through a ...
7
votes
3answers
2k views

Piping STDERR vs. STDOUT

According to "Linux: The Complete Reference 6th Edition" (pg. 44), you can pipe only STDERR using the |& redirection symbols. I've written a pretty simple script to test this: #!/bin/bash echo ...
9
votes
3answers
5k views

Non-blocking buffered named pipe?

I'm looking for something I suspect doesn't exist: A non-blocking buffered named pipe (fifo) for use from the command line. Is there such a thing? Here's the use case: Suppose I have a process that's ...
3
votes
3answers
2k views

Create a temporary file from a stdout redirect or pipe

Some commands only output to stdout. Some tools only work on files. Is there a command that can glue those together? Contrived simple example: diff $(echo 1 | stdout-to-temp-file) $(echo 2 | ...
2
votes
2answers
1k views

Difference between > and | with /dev/tty

When I run this command: echo "1" > /dev/tty # runs successfully but when I run this: echo "1" | /dev/tty #permission denied What is the difference between these two operators > and | and ...
10
votes
4answers
17k views

Difference between 2>&1 > output.log and 2>&1 | tee output.log

I wanted to know the difference between the following two commands 2>&1 > output.log and 2>&1 | tee output.log I saw one of my colleague use second option to redirect. I know ...
5
votes
2answers
1k views

Performance difference between stdin and command line argument

For some commands, it is possible to specify certain input as either stdin or a command line argument. Specifically, suppose command can take stdin input and a filename as command line argument, and ...
19
votes
4answers
2k views

Process substitution and pipe

I was wondering how to understand the following: Piping the stdout of a command into the stdin of another is a powerful technique. But, what if you need to pipe the stdout of multiple ...
0
votes
1answer
235 views

Is 'some_program <some_file' faster than 'cat some_file | some_program'? [duplicate]

Possible Duplicate: Should I care about unnecessary cats? Both would be functionally equivalent, but when using cat wouldn't it be slower because you have a process first reading the file ...
3
votes
2answers
1k views

Why is piped input okay to zenity, but <file malfunctions?

My question is as simple as what the zenity --text args say in the example... but what is causing this 100% CPU grab by the redirection? ...(and by the way, is this particular usage of < actually ...
6
votes
2answers
857 views

redirection and pipeline

I was wondering about differences and relation between redirection and pipeline. Is pipeline only used to connect stdout output of a command to stdin input of another command? Is redirection only ...
7
votes
3answers
4k views

Redirect stdout over ssh

I would like to run something > file on a remote system through ssh, but if I run ssh host something > file the redirection is executed locally as ssh etc > file I've tried it with ' ...