In this tutorial, I will write about Useful shell commands. Tips and trick about kill process, How to remove ssh host and SCP command. Bash script the essential for DevOps Roles.

Useful shell commands

Kill Process

ps aux | grep <keyword> | grep -v grep | awk '{ print "kill -9", $2 }' | sh

For example, How to kill running Tilix process as the picture below

Kill the process Tilix

[huupv@huupv devopsroles]$ ps aux | grep tilix | grep -v grep | awk '{ print "kill -9", $2 }' | sh

How to remove ssh host

ssh-keygen -R <IP address/host_name>

SCP command

Upload to server

scp -i <ssh key private file> -r <local directory/file> <user>@<remote server>:<remote directory/file>

Download from server

scp -i <ssh key private file> -r <user>@<remote server>:<remote directory/file> <local directory/file>

In this tutorial, I am written a small program with “Bash script copy rename multiple files” on Linux. Linux the essential for DevOps Roles.

The syntax for the loop

for file in $(ls)
do
       cp $file ${file/<Pattern>/<Replacement>}; 
done

For example, I will copy and rename 2 files “foo2017-2.txt and foo2017-3.txt” into “foo2018-2.txt and foo2018-3.txt”  in “folder” folder.

[huupv@huupv devopsroles]$ pwd
/home/huupv/devopsroles
[huupv@huupv devopsroles]$ ls folder/
file.txt foo2017-1.txt foo2017-2.txt foo2017-3.txt
[huupv@huupv devopsroles]$

My Bash script copy rename multiple files

#!/bin/bash
#Only 2 copies files from the bottom and change 2017 to 2018

FOLDER=$1;
for file in $(ls $FOLDER/ | tail -n2)
do
   cp ${FOLDER}/${file} ${FOLDER}/${file/2017/2018};
done

Execute bash script

[huupv@huupv devopsroles]$ chmod +x bash_rename_files.sh
[huupv@huupv devopsroles]$ ./bash_rename_files.sh /home/huupv/devopsroles/folder

The result, after you run the bash script

[huupv@huupv devopsroles]$ ls /home/huupv/devopsroles/folder/
file.txt foo2017-1.txt foo2017-2.txt foo2017-3.txt foo2018-2.txt foo2018-3.txt
[huupv@huupv devopsroles]$

The screen output terminal

In this tutorial, How do I use Linux shell script tips? shell script the essential for DevOps Roles.

Linux shell script tips

Load any functions file into the current shell script or a command prompt.

# source command
source ~/.bashrc
# or .
. ~/.bashrc

Do not display output on terminal

[huupv@huupv devopsroles]$ echo devopsroles > /dev/null 2>&1

To display the time in the upper right corner on the terminal

[huupv@huupv devopsroles]$ while sleep 1;do tput sc;tput cup 0 $(($(tput cols)-30));date;tput rc;done &

The screen output terminal as below

Linux date 7 days ago

[huupv@huupv devopsroles]$ date +"%Y-%m-%d" --date "-7 day"

The screen output terminal as below

Waiting for background processes to finish

[huupv@huupv devopsroles]$ sleep 100 & wait $!

Positional parameters in Linux

[huupv@huupv devopsroles]$ foo=(dev ops COM)
[huupv@huupv devopsroles]$ echo ${foo[2]:0}
>COM

Handling arrays in the shell script

[huupv@huupv devopsroles]$ foo=(x y z)
[huupv@huupv devopsroles]$ echo ${foo[2]}
>z
[huupv@huupv devopsroles]$ echo ${#foo}
>1

URL tips

[huupv@huupv devopsroles]$ url=https://www.devopsroles.com/huupv

If you want to retrieve user

$ echo ${url##*/}
> huupv

Retrieve the domain

[huupv@huupv devopsroles]$ echo ${url%/*}
> https://www.devopsroles.com

You want to retrieve the protocol

[huupv@huupv devopsroles]$ echo ${url%%/*}
> https:

The screen output terminal as below

In this tutorial, I have written a small program opening application by the shell script. Linux the essential for DevOps Roles.
I will create the directory and create a file openapp. Let’s begin!

[huupv@huupv devopsroles]$ mkdir myall && cd $_
[huupv@huupv myall]$ pwd
/home/huupv/devopsroles/myall
[huupv@huupv myall]$ touch openapp

Bash script opening application

#!/bin/bash

if [ $1 = "fb" ]; then
  echo Opening facebook
  python -m webbrowser -t "https://www.facebook.com/"
elif [ $1 = "web" ]; then
  echo Opening My Website 
  python -m webbrowser -t "https://www.devopsroles.com/"
  python -m webbrowser -t "https://www.huuphan.com/"
elif [ $1 = "youtube" ]; then
  echo Opening youtube
  python -m webbrowser -t "https://www.youtube.com/user/SystemOperatinglinux"
fi

Add permission to execute.

[huupv@huupv myall]$ chmod +x openapp

Now, I opening Youtube with my shell script.

[huupv@huupv myall]$ ./openapp youtube

The screen output terminal as below