How to run Linux commands every X seconds
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How to run Linux commands every X seconds
In this article we will explain how to run Linux Linux commands every X seconds and how System administrators runs commands for certain period of time.
Options of watch command
-b &ndash creates a beep sound if the exit of the command is non-zero.
-c &ndash Interprets ANSI color sequences.
-d &ndash highlights the changes in the command output.
Using Watch Command
It helps to execute the commands every 2 seconds.
To Monitor Memory usage
watch free -m
Output
Every 2.0s: free -m Sat Mar 5 00:01:59 2016
total used free shared buffers cached
Mem: 988 533 455 3 32 201
-/+ buffers/cache: 299 688
Swap: 1999 0 1999
-n option is used to specify the interval when the command will be executed. -d option is used to highlight the changes in the output.
Every 5.0s: sh script.sh Sat Mar 5 00:13:55 2016
total 596
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
total used free shared buffers cached
Mem: 988 545 443 4 33 208
-/+ buffers/cache: 303 684
Swap: 1999 0 1999
To monitor logged-in users
Example
[user1@linuxhelp ~]$ watch uptime
Every 2.0s: uptime Sat Mar 5 00:17:32 2016
00:17:32 up 1:18, 2 users, load average: 0.00, 0.00, 0.00
To exit the command
Press CTRL+C
The up time command will run and display the updated commands results every 2 seconds.
To monitor progress copy command
Example
[user1@linuxhelp Desktop]$ cp ubuntu-10.04.1-server-amd64.iso /home/user1/new/
[user1@linuxhelp Desktop]$ watch -n 2 du -s /home/user1/new/
Every 2.0s: du -s /home/user1/new/ Sat Mar 5 00:31:10 2016
698880 /home/user1/new/
Using sleep Command for loop
Example
[user1@linuxhelp ~]$ for i in {1..3} do ll date sleep 3 done
total 700076
drwxrwxr-x 2 user1 user1 4096 Mar 5 00:28 new
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 715644928 Sep 30 2010 ubuntu-10.04.1-server-amd64.iso
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
-rw-rw-r-- 1 user1 user1 287944 Mar 5 00:17 watch 3.png
-rw-rw-r-- 1 user1 user1 322083 Mar 5 00:31 watch 4.png
Sat Mar 5 00:48:35 IST 2016
total 700076
drwxrwxr-x 2 user1 user1 4096 Mar 5 00:28 new
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 715644928 Sep 30 2010 ubuntu-10.04.1-server-amd64.iso
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
-rw-rw-r-- 1 user1 user1 287944 Mar 5 00:17 watch 3.png
-rw-rw-r-- 1 user1 user1 322083 Mar 5 00:31 watch 4.png
Sat Mar 5 00:48:39 IST 2016
total 700076
drwxrwxr-x 2 user1 user1 4096 Mar 5 00:28 new
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 715644928 Sep 30 2010 ubuntu-10.04.1-server-amd64.iso
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
-rw-rw-r-- 1 user1 user1 287944 Mar 5 00:17 watch 3.png
-rw-rw-r-- 1 user1 user1 322083 Mar 5 00:31 watch 4.png
Sat Mar 5 00:48:42 IST 2016
Using while loop
Example
[user1@linuxhelp ~]$ while true do ll date sleep 3 done
total 700444
drwxrwxr-x 2 user1 user1 4096 Mar 5 00:28 new
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 715644928 Sep 30 2010 ubuntu-10.04.1-server-amd64.iso
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
-rw-rw-r-- 1 user1 user1 287944 Mar 5 00:17 watch 3.png
-rw-rw-r-- 1 user1 user1 322083 Mar 5 00:31 watch 4.png
-rw-rw-r-- 1 user1 user1 374098 Mar 5 00:51 watch 5.png
Sat Mar 5 00:57:23 IST 2016
total 700444
drwxrwxr-x 2 user1 user1 4096 Mar 5 00:28 new
-rw-rw-r-- 1 user1 user1 14 Mar 5 00:05 script.sh
-rw-rw-r-- 1 user1 user1 715644928 Sep 30 2010 ubuntu-10.04.1-server-amd64.iso
-rw-rw-r-- 1 user1 user1 297690 Mar 5 00:01 watch 1.png
-rw-rw-r-- 1 user1 user1 304451 Mar 5 00:13 watch 2.png
-rw-rw-r-- 1 user1 user1 287944 Mar 5 00:17 watch 3.png
-rw-rw-r-- 1 user1 user1 322083 Mar 5 00:31 watch 4.png
-rw-rw-r-- 1 user1 user1 374098 Mar 5 00:51 watch 5.png
Sat Mar 5 00:57:26 IST 2016
total 70044
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