Ttyjfyk

I Accidentally Deleted a Stock Terminal Theme

Can I ask the recruiters in my resume to put the reason why I am rejected?

"You are your self first supporter", a more proper way to say it

Can the number of solutions to a system of PDEs be bounded using the characteristic variety?

meaning of に in 本当に?

How to format long polynomial?

Uncaught TypeError: 'set' on proxy: trap returned falsish for property Name

Two films in a tank, only one comes out with a development error – why?

What would happen to a modern skyscraper if it rains micro blackholes?

When a company launches a new product do they "come out" with a new product or do they "come up" with a new product?

Why is 150k or 200k jobs considered good when there's 300k+ births a month?

How can bays and straits be determined in a procedurally generated map?

Maximum likelihood parameters deviate from posterior distributions

What's that red-plus icon near a text?

Get value of a counter

Theorems that impeded progress

What is the word for reserving something for yourself before others do?

Could an aircraft fly or hover using only jets of compressed air?

expand `ifthenelse` immediately

What is a clear way to write a bar that has an extra beat?

Did Shadowfax go to Valinor?

Can a Cauchy sequence converge for one metric while not converging for another?

Is it inappropriate for a student to attend their mentor's dissertation defense?

Is it legal for company to use my work email to pretend I still work there?

Output redirection is not working with top piped to grep

In what order do piped commands run?Pipes & redirection binding precedence with disjuncts, conjuncts etc?Where does network waiting go in 'top'?append mode in Centos and UbuntuHow is the “load average” interpreted in “top” output? Is it the same for all distributions?Raspbian: problem with output redirection in udev scripttop command not workingWhy does total tasks listed in 'top' command output not equal running + sleeping?StdOut redirection not workingmulti-core CPU usage

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

3

1

When I run this command in Linux:

$ top -b -d 20 | grep "load average" -A 20 > top.log

top.log is always empty.

But when I run this command:

$ top -b -d 20 | grep "load average" -A 20 | tee top.log

then top.log has contents.

If I don't want to use tee (because I don't want the output to be displayed onto the console), how do I correct the first command so that top.log is updated?

My machine uses CentOS Linux 7 (Core).

centos pipe io-redirection top

share|improve this question

asked Mar 27 at 10:19

kurtkurt

1183

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  weird. In my Cento7 machine, both commands work well.
  
  – JinChin
  Mar 27 at 10:29
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  if you want only load average, why not use uptime ?
  
  – Archemar
  Mar 27 at 10:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Archemar What is the -A option of grep for?
  
  – Uncle Billy
  Mar 27 at 10:33
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Archemar @UncleBilly, i'm using a trick for limiting the amount of entries returned by top.
  
  – kurt
  Mar 27 at 10:36
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @UncleBilly Ah, yes that is the catch ...
  
  – Archemar
  Mar 27 at 10:38
  

  
  
  
  

add a comment | 

3

1

When I run this command in Linux:

$ top -b -d 20 | grep "load average" -A 20 > top.log

top.log is always empty.

But when I run this command:

$ top -b -d 20 | grep "load average" -A 20 | tee top.log

then top.log has contents.

If I don't want to use tee (because I don't want the output to be displayed onto the console), how do I correct the first command so that top.log is updated?

My machine uses CentOS Linux 7 (Core).

centos pipe io-redirection top

share|improve this question

asked Mar 27 at 10:19

kurtkurt

1183

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  weird. In my Cento7 machine, both commands work well.
  
  – JinChin
  Mar 27 at 10:29
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  if you want only load average, why not use uptime ?
  
  – Archemar
  Mar 27 at 10:29
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Archemar What is the -A option of grep for?
  
  – Uncle Billy
  Mar 27 at 10:33
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Archemar @UncleBilly, i'm using a trick for limiting the amount of entries returned by top.
  
  – kurt
  Mar 27 at 10:36
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @UncleBilly Ah, yes that is the catch ...
  
  – Archemar
  Mar 27 at 10:38
  

  
  
  
  

add a comment | 

When I run this command in Linux:

$ top -b -d 20 | grep "load average" -A 20 > top.log

top.log is always empty.

But when I run this command:

$ top -b -d 20 | grep "load average" -A 20 | tee top.log

then top.log has contents.

If I don't want to use tee (because I don't want the output to be displayed onto the console), how do I correct the first command so that top.log is updated?

My machine uses CentOS Linux 7 (Core).

centos pipe io-redirection top

share|improve this question

asked Mar 27 at 10:19

kurtkurt

1183

$ top -b -d 20 | grep "load average" -A 20 > top.log

$ top -b -d 20 | grep "load average" -A 20 | tee top.log

share|improve this question

asked Mar 27 at 10:19

kurtkurt

1183

share|improve this question

asked Mar 27 at 10:19

kurtkurt

1183

asked Mar 27 at 10:19

kurtkurt

1183

asked Mar 27 at 10:19

kurtkurt

1183

2 Answers
2

active

oldest

votes

3

You should use the --line-buffered option of grep (since your question is tagged "centos", you're most certainly using GNU grep).

By default, grep will only use line buffering when the output is a terminal (just like stdio functions: printf, puts, etc). The --line-buffered option is overriding that. GNU coreutils also has a stdbuf(1) wrapper that should work with any dynamically linked program which is using stdio.

share|improve this answer

edited Mar 27 at 10:32

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

add a comment | 

-1

You can use cat /proc/loadavg at intervals. Why pull it from top? It is intended for active monitoring (mostly), and will always use more resources than a fast read of loadavg. For the process listing, just use ps, and sort with the —sort flag. E.g.

( while true ; do cat /proc/loadavg ; ps -aux | sort -nrk 3,3 | head -n 20 ; sleep 3 ; done ; ) | pipe ...

or

( while true ; do cat /proc/loadavg ; ps -Ao user,uid,pid,comm,pcpu,tty —sort=-pcpu —no-headers | head -n 20 ; sleep 3 ; done ; ) | pipe ...

share|improve this answer

edited Mar 28 at 6:38

answered Mar 28 at 3:08

user2497user2497

603137

add a comment | 

Your Answer

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "106"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f508935%2foutput-redirection-is-not-working-with-top-piped-to-grep%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

3

You should use the --line-buffered option of grep (since your question is tagged "centos", you're most certainly using GNU grep).

By default, grep will only use line buffering when the output is a terminal (just like stdio functions: printf, puts, etc). The --line-buffered option is overriding that. GNU coreutils also has a stdbuf(1) wrapper that should work with any dynamically linked program which is using stdio.

share|improve this answer

edited Mar 27 at 10:32

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

add a comment | 

3

You should use the --line-buffered option of grep (since your question is tagged "centos", you're most certainly using GNU grep).

By default, grep will only use line buffering when the output is a terminal (just like stdio functions: printf, puts, etc). The --line-buffered option is overriding that. GNU coreutils also has a stdbuf(1) wrapper that should work with any dynamically linked program which is using stdio.

share|improve this answer

edited Mar 27 at 10:32

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

add a comment | 

You should use the --line-buffered option of grep (since your question is tagged "centos", you're most certainly using GNU grep).

By default, grep will only use line buffering when the output is a terminal (just like stdio functions: printf, puts, etc). The --line-buffered option is overriding that. GNU coreutils also has a stdbuf(1) wrapper that should work with any dynamically linked program which is using stdio.

share|improve this answer

edited Mar 27 at 10:32

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

share|improve this answer

edited Mar 27 at 10:32

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

answered Mar 27 at 10:26

Uncle BillyUncle Billy

9348

-1

You can use cat /proc/loadavg at intervals. Why pull it from top? It is intended for active monitoring (mostly), and will always use more resources than a fast read of loadavg. For the process listing, just use ps, and sort with the —sort flag. E.g.

( while true ; do cat /proc/loadavg ; ps -aux | sort -nrk 3,3 | head -n 20 ; sleep 3 ; done ; ) | pipe ...

or

( while true ; do cat /proc/loadavg ; ps -Ao user,uid,pid,comm,pcpu,tty —sort=-pcpu —no-headers | head -n 20 ; sleep 3 ; done ; ) | pipe ...

share|improve this answer

edited Mar 28 at 6:38

answered Mar 28 at 3:08

user2497user2497

603137

add a comment | 

-1

You can use cat /proc/loadavg at intervals. Why pull it from top? It is intended for active monitoring (mostly), and will always use more resources than a fast read of loadavg. For the process listing, just use ps, and sort with the —sort flag. E.g.

( while true ; do cat /proc/loadavg ; ps -aux | sort -nrk 3,3 | head -n 20 ; sleep 3 ; done ; ) | pipe ...

or

( while true ; do cat /proc/loadavg ; ps -Ao user,uid,pid,comm,pcpu,tty —sort=-pcpu —no-headers | head -n 20 ; sleep 3 ; done ; ) | pipe ...

share|improve this answer

edited Mar 28 at 6:38

answered Mar 28 at 3:08

user2497user2497

603137

add a comment | 

You can use cat /proc/loadavg at intervals. Why pull it from top? It is intended for active monitoring (mostly), and will always use more resources than a fast read of loadavg. For the process listing, just use ps, and sort with the —sort flag. E.g.

( while true ; do cat /proc/loadavg ; ps -aux | sort -nrk 3,3 | head -n 20 ; sleep 3 ; done ; ) | pipe ...

or

( while true ; do cat /proc/loadavg ; ps -Ao user,uid,pid,comm,pcpu,tty —sort=-pcpu —no-headers | head -n 20 ; sleep 3 ; done ; ) | pipe ...

share|improve this answer

edited Mar 28 at 6:38

answered Mar 28 at 3:08

user2497user2497

603137

share|improve this answer

edited Mar 28 at 6:38

answered Mar 28 at 3:08

user2497user2497

603137

answered Mar 28 at 3:08

user2497user2497

603137

answered Mar 28 at 3:08

user2497user2497

603137