Questions tagged [output]
The output tag has no usage guidance.
46
questions
231
votes
7
answers
638k
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 store ...
- 2,311
112
votes
5
answers
363k
views
Save all the terminal output to a file
Is there some way of saving all the terminal output to a file with a command?
I'm not talking about redirection command > file.txt
Not the history history > file.txt, I need the full terminal ...
user78927
72
votes
4
answers
243k
views
how to output text to both screen and file inside a shell script?
Currently I have a shell script which logs messages to a log file like this:
log_file="/some/dir/log_file.log"
echo "some text" >> $log_file
do_some_command
echo "more text" >> $log_file
...
- 823
23
votes
2
answers
5k
views
What prevents stdout/stderr from interleaving?
Say I run some processes:
#!/usr/bin/env bash
foo &
bar &
baz &
wait;
I run the above script like so:
foobarbaz | cat
as far as I can tell, when any of the processes write to stdout/...
- 10.4k
1
vote
2
answers
1k
views
Output colored text in all major distros without using non-word color codes (like \033[0;31m)
I found these ways, for example, to output colored text in a simple way to the screen:
RED="\033[0;31m" # Red color (via ANSI escape code);
NC='\033[0m' # No color (via ANSI escape code);
echo -e "${...
user149572
41
votes
6
answers
65k
views
How do I add newlines between lines printed on the command line?
Mail logs are incredibly difficult to read. How could I output a blank line between each line printed on the command line? For example, say I'm grep-ing the log. That way, multiple wrapped lines aren'...
- 59.8k
15
votes
3
answers
17k
views
How to redirect the output of any command?
I'm trying to write a simple script to monitor my network status, without all of ping's output:
ping -q -c 1 google.com > /dev/null && echo online || echo offline
The problem is that when ...
- 371
26
votes
3
answers
112k
views
Capture all the output of a script to a file (from the script itself) [duplicate]
I have a bash script that calls various commands and prints some output (both from the called commands themselves, such as git pull, and informative messages generated by the script itself such as ...
24
votes
5
answers
26k
views
Pipe the output of a command if it is successful
INPUT_FILE=`ls -rt $MY_DIR/FILE.*.xml | head -1 | xargs basename`
I wanted to execute the second command (head -1) only if the first command is successful. How do I improve this command?
- 1,431
18
votes
3
answers
24k
views
Where does the output of `at` and `cron` jobs go?
Where does standard output from at and cron tasks go, given there
is no screen to display to?
It's not appearing in the directory the jobs were started from, nor in
my home directory.
How could I ...
- 42.6k
11
votes
1
answer
10k
views
redirecting output of running background job in bash
in bash I have some jobs running, in background. They are always producing random irrelevant error messages that pollute the terminal. I am not always so prompt to start them with the 2>&1 > ...
- 900
11
votes
3
answers
3k
views
Keep terminal input line at the top of the terminal?
It's really hard to explain what I am looking for exactly so I have made some example output of how I would like my terminal to behave. (each number at the start of a line represents a return on that ...
- 211
9
votes
2
answers
13k
views
Log output of GNU screen in real time?
I'm trying to get the output of a GNU Screen to a log file in real time. I've tried using tee, but that appears to not work with screen. The log function for screen will not work for this as it is not ...
- 183
8
votes
2
answers
3k
views
double grep on tail -f gives no output
If I follow a file somehow like this:
tail -f /var/log/syslog|grep s
I see all lines containing an "s"
Why does this not give any output, if I grep it again to the same "s"?
tail -f /var/log/...
- 29.6k
6
votes
1
answer
11k
views
Evaluating the return value of a command line
How do I evaluate or calculate the return value of a command line?
For exemple, I count the number of lines with a grep and I want to know if that value is above X. If so, I want to print the number ...
4
votes
2
answers
22k
views
How can I get vsftpd version into shell variable?
I want to get vsftpd version into shell variable. I can get it to console with ease:
# vsftpd -version
vsftpd: version 2.2.2
Also I can get a lot of other info into variable:
# i=`bash --version 2&...
- 886
3
votes
2
answers
23k
views
Get the output from expect script in a variable
I have an expect script which provides the IP address:
#!/bin/expect -f
set nodename [lindex $argv 0]
spawn virsh console $nodename
expect "Escape character is"
send "\n"
expect "localhost login: " {
...
3
votes
1
answer
454
views
Why is shell treating a part of the output of $(<file) as a command?
I saw this line while reading a blog on IFS that is :
for i in $(<test.txt)
And thought that $(<test.txt) prints the file contents to STDOUT. I maybe wrong in this, but out of curiosity I ...
- 828
1
vote
2
answers
6k
views
Redirect grep error output to file
I wanted to capture to a file the errors being returned on the command line from grep. For example,
grep foo.lookup
No such file in directory
I want to output that to a log file. This is my shell ...
- 325
1
vote
4
answers
370
views
Shell command to put recent line of output onto current command line
Shells have a useful feature where pressing the keyboard UP arrow replaces the contents of the current command line with the previous command that was entered. (And if you do it again, the command ...
- 258
-3
votes
2
answers
1k
views
What is the utility of piping to `/dev/null`?
Seeing that /dev/null's utility isn't immediately obvious to me, what is the use of /dev/null piping?
85
votes
10
answers
61k
views
Converting colored output into html
There are tools providing coloured output:
dwdiff -c File1 File2 # word level diff
grep --color=always # we all know this guy
...
The question is: How to convert their colored output of arbitrary ...
- 14.5k
23
votes
3
answers
3k
views
How to prevent random console output from breaking the terminal?
There are many questions on SE that show how to recover from terminal broken by cat /dev/urandom. For those that are unfamiliar with this issue - here what it is about:
You execute cat /dev/urandom ...
- 983
21
votes
4
answers
25k
views
Why does this 'at' command not print to the standard output?
I am a relative Linux novice. I am trying to learn how to use at so that I can schedule tasks to begin at a later time, without using sleep. I have been looking at this previous question for help.
...
- 17.2k
17
votes
3
answers
37k
views
Suppress 'file truncated' messages when using tail
I'm tailing a log file using tail -f messages.log and this is part of the output:
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Fusce eget tellus sit amet odio porttitor rhoncus.
Donec ...
- 247
17
votes
1
answer
11k
views
Show only graph in htop output
Would it be possible to show only the summary section of htop output?
desired look:
I have looked into the manpages but couldn't find any options to do so.
The closest thing i have found is this: ...
- 393
14
votes
5
answers
46k
views
How do I get (only) the http status of a site in a shell script?
I figure curl would do the job. I wrote in a script:
#!/bin/sh
function test {
res=`curl -I $1 | grep HTTP/1.1 | awk {'print $2'}`
if [ $res -ne 200 ]
then
echo "Error $res on $1"...
user4069
14
votes
6
answers
121k
views
How can I output the difference between 2 files?
My file consists of the the following; roughly:
username:username:username:username:username
The above line continues to about 600 characters.
I use the awk command in order to use it as an ...
- 315
10
votes
4
answers
865
views
Save output of command that modifies environment into a variable
How to save output of a command that modifies environment into a variable?
I'm using bash shell.
Assume that I have:
function f () { a=3; b=4 ; echo "`date`: $a $b"; }
And now, I can use commands ...
- 215
7
votes
4
answers
2k
views
Output current day using cal
I'm asked to output the current day using the cal command.
So far, I discovered that before the current date there is a _ symbol. I decided to use grep here: cal | grep '\b_*', but it outputs the ...
- 181
7
votes
1
answer
11k
views
Why can't an input file be an output file?
Specifically in the case of cat x y > y and cat x >> x where x and y are files.
What would happen if I didn't get a "input file is output file" error? Basically, why am I not allowed to run ...
- 71
5
votes
1
answer
3k
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 ...
- 10.7k
5
votes
4
answers
28k
views
Changing audio output from terminal
I have a Xonar DGX card, and I can change the audio output with alsamixer by going to the Analog Output option and switching between Stereo Headphones and Stereo Headphones FP. How can I do the same ...
- 151
4
votes
1
answer
13k
views
How to disable VLC output in command-line mode?
When I play music on vlc or cvlc in terminal or console there is always this (shown below) non-stopping output that prevents me from issuing commands by pressing ENTER key. I want to disable it, I ...
- 2,038
4
votes
2
answers
2k
views
Limit stdout from a continuously running process
I haven't had much luck finding an answer to my problem, but maybe I'm not asking for it correctly.
I have a process I startup like the following:
nohup ping 127.0.0.1 > log.txt >2>&1 &
...
- 43
3
votes
2
answers
6k
views
Redirect Output of Pocketsphinx_continuous to a file
I have an ugly command:
pocketsphinx_continuous -samprate 48000 -nfft 2048 -hmm /usr/local/share/pocketsphinx/model/en-us/en-us -lm 9745.lm -dict 9745.dic -inmic yes
Breakdown: It listens for any ...
- 251
3
votes
4
answers
6k
views
Leave remote command running storing output
Scenario;
I have SSH'ed to a machine, opened a new screen session, and fired off a script.
Some days later I SSH back to that machine, re-attach the screen session and look at the output that has ...
- 7,782
3
votes
1
answer
2k
views
Get the output of the time command
I have the following command
time compare -metric rmse -subimage-search -dissimilarity-threshold 1 -similarity-threshold 0.99 $page \( -size 1x1 xc:black \) null:
which produces the following ...
- 343
2
votes
1
answer
6k
views
Pipe output from one command to another command's non standard input [duplicate]
I would like to do something similar to the following:
which someapplciation | cd outputfrompreviouscommand
The command which provides a directory and I would like to be able to make that output my ...
- 23
2
votes
2
answers
222
views
How do I echo a line with linebreak at the end at window border? [duplicate]
I would like to echo a list all in one line, TAB separated (like ls does with files in one folder)
for i in one two some_are_very_long_stuff b c; do echo $i; done
will print one line per word:
one
...
- 29.6k
2
votes
1
answer
9k
views
how do i redirect output from tailf & grep to a file [duplicate]
All I wanted is to grep for specific lines in an ongoing log and re-direct it to some file..
tailf log | grep "some words"
Now, I want the above command output to get re-directed to some file in on-...
- 1,071
2
votes
1
answer
581
views
Sending `time` command into text file [duplicate]
I want to get the result of time command into a text file but it's not working it only put blank space in the text file.
I already tried this commands,
A-
$ x=`time`
$ echo $x > log.txt
$ cat ...
- 395
1
vote
2
answers
2k
views
Do all Linux processes write EOF to stdout when they are terminating/have finished terminating?
I'm having trouble with sending shutdown -h 0 to a lxc Debian container (i.e. executing this command in the lxc) with with the python pexpect module (in a python script). In this module the user can "...
- 2,211
1
vote
2
answers
1k
views
Echo calculation to text file [duplicate]
I am working on a project to calculate my overtime at work with a shell script. I have two inputs and want to find if my number is over 800 = 8 hours;
if it is bigger, then it has to print out the ...
- 17
0
votes
3
answers
9k
views
sudo iwlist wlan0 scan | grep ESSID > essid.txt (How do I export without the word ESSID in txt file)
So my goal is to answer my other question I am working on. Which is Connect to Open Wifi. Currently I am getting close, as I know there is only one Wifi connection, I would like to export the results ...
- 2,622
-1
votes
1
answer
83
views
Why output is on the prompt line?
$ echo 'hello world' > >(wc)
$ 1 2 12
█
Why output is on the prompt line and not in the separate line below?
Also why expects input at the end?
Since, the command below works fine ...
