Introduction

In this tutorial, we will explore the tr command in Linux, a versatile utility in Linux for translating or deleting characters in text. The tr command is primarily used for character-level transformations, making it an essential tool for modifying the contents of text files or input streams. By specifying certain rules, tr allows you to replace or remove specific characters efficiently. Let’s dive into practical examples to see the using tr command in Linux.

What is the purpose of the tr command?

The tr command, short for “translate,” is a powerful utility in Linux used to translate or delete characters in text data. It performs specific transformations on the contents of a file or data from a standard input, based on rules defined by the user.

tr command syntax

tr [OPTION]... [INPUT [OUTPUT]]

According to the man page, it is described as follows.

• tr – translate or delete characters.
• man tr – More details information about tr command.

tr command in Linux with an example

I have created a file tr_command.txt as below

[vagrant@DevopsRoles ~]$ cat tr_command.txt 
 HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x.
 Devops Roles.
 Devops Roles.
 Devops Roles.
 Devops Roles.
 Hello world :)

How to convert small letters into capital letters.

[vagrant@DevopsRoles ~]$ cat tr_command.txt | tr [:lower:] [:upper:]           
 HUUPV, MY WEBSITE DEVOPSROLES.COM AND HUUPHAN.COM.SN:199X.
 DEVOPS ROLES.
 DEVOPS ROLES.
 DEVOPS ROLES.
 DEVOPS ROLES.
 HELLO WORLD :)

The following command is used to convert each space of the text by a newline (\n)

[vagrant@DevopsRoles ~]$ cat tr_command.txt | tr [:space:] '\n'                                                                                                            
 HuuPV,
 My
 website
 DevopsRoles.com
 and
 HuuPhan.com.SN:199x.
 Devops
 Roles.
 Devops
 Roles.
 Devops
 Roles.
 Devops
 Roles.
 Hello
 world
 :)

uses –s option for searching and replacing any string from a text

[vagrant@DevopsRoles ~]$ cat tr_command.txt |  tr -s ' ' '\t'
 HuuPV,  My      website DevopsRoles.com and     HuuPhan.com.SN:199x.
 Devops  Roles.
 Devops  Roles.
 Devops  Roles.
 Devops  Roles.
 Hello   world   :)

Delete numbers

[vagrant@DevopsRoles ~]$ cat tr_command.txt | tr -d "[:digit:]"
 HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:x.
 Devops Roles.
 Devops Roles.
 Devops Roles.
 Devops Roles.
 Hello world :)

Output the converted output to a file

[vagrant@DevopsRoles ~]$ cat tr_command.txt | tr "[:upper:]" "[:lower:]" > result_tr.txt 

Conclusion

The tr command is a straightforward yet powerful tool in Linux, used to translate or delete characters in text. For more detailed information and to explore additional options that may vary by Linux distribution, you can consult the manual page for the tr command by typing man tr in the terminal. Thank you for visiting the DevopsRoles page!

Introduction

In this tutorial, I am using the cut command in Linux to remove sections from each line of files.

The cut the command is used to extract specific sections (columns) from lines of input text or files in Linux and Unix systems. It is particularly useful for working with delimited data.

What does cut command mean?

cut – remove sections from each line of files

Syntax

cut OPTION... [FILE]...

On the man page, the description it

• cut – remove sections from each line of files.
• man cut – More details information about the cut command.

cut command in Linux with an example

I have created a file cut_command.txt as below

[vagrant@DevopsRoles ~]$ cat cut_command.txt 
 HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x.
 Devops Roles.
 Hello world. xxx.

For delimiter-separated fields. The default delimiter is the tab character.

[vagrant@DevopsRoles ~]$ cut -d "," -f 1 cut_command.txt 
 HuuPV
 Devops Roles.
 Hello world. xxx

Get a list of all users in the Linux

[vagrant@DevopsRoles ~]$ cat /etc/passwd | cut -d ':' -f1                                                                                                                                                                              
 root
 bin
 daemon
 adm
 lp
 sync
 shutdown
 halt
 mail
 uucp
 operator
 games
 gopher
 ftp
 nobody
 vcsa
 rpc
 rpcuser
 nfsnobody
 sshd
 exim
 centos
 huupv
 gluster
 grafana
 influxdb
 mysql
 acc1
 netdata
 telegraf
 nginx
 dbus
 haldaemon

cut and sort sort

[vagrant@DevopsRoles ~]$ cat /etc/passwd | grep home | cut -d: -f1,6 | sort
 acc1:/home/acc1
 huupv:/home/huupv

You can also display the table with column -t

[vagrant@DevopsRoles ~]$ cat /etc/passwd | grep home | cut -d: -f1,6 | sort | tr ":" " "  | column -t
 acc1      /home/acc1                                                           
 huupv    /home/huupv

Extract a range of fields

cut -f 2-4 file.txt

Print a specific delimiter

cut -d ',' -f 2 --output-delimiter=" | " file.csv

Read input from a pipe

echo "data1,data2,data3" | cut -d ',' -f 2

Conclusion

cut command in Linux is a simple command in Linux. It is used to remove sections from each line of files.

These are just a few examples of how you can use the cut command. It offers various options and functionalities for extracting specific sections from text or files. You can refer to the cut man page (man cut) for more details and additional options.

Thank you for reading the DevopsRoles page!

Good morning, I am working and changing the ownership folder of my home, but I cannot run chown command. It is Error “Invalid argument”. This is indeed an NFS4 issue. The error chown Invalid argument as following below:

[root@Client ~]# chown -R huupv:huupv /home/huupv                                                    
chown: changing ownership of `huupv/.bashrc': Invalid argument
chown: changing ownership of `huupv': Invalid argument

My environment

Client <---> NFS server

How can I fix the chown Invalid argument this

You need to check step by step as below:

NFS client:

[root@Client ~]# cat /etc/redhat-release
Centos 6

NFS Server

[root@DevopsRoles ~]# cat /etc/redhat-release
Centos 7

Configure NFS server

[root@DevopsRoles ~]# cat /etc/exports

The Content in file exports

#Data Volume Share
/mnt/data 192.168.1.12(rw,sync,no_root_squash,no_subtree_check)

Solve Problem

From the Client, we will umount and mount as below

[root@Client ~]# umount /mnt/data # if umount is busy then you need run umount -lf /mnt/data
[root@Client ~]# mount -t nfs -o vers=3 192.168.1.13:/mnt/data  /mnt/data
[root@Client ~]# chown -R huupv:huupv /home/huupv

You have solved the problem “chown Invalid argument centos” Thank you for reading the DevopsRoles page!

In this tutorial, How to run Spring Boot Application as a service in Linux. Spring boot preferred deployment method via an executable jar file that contains tomcat inside.

Spring Boot application as a service

Spring Boot and Systemd

Create new file “/etc/systemd/system/myapp.service” as a service to start on reboot.

[Unit]
Description=myapp
After=syslog.target
[Service]
User=myapp
ExecStart=/var/myapp/myapp.jar
SuccessExitStatus=143
Restart=always
RestartSec=30
[Install]
WantedBy=multi-user.target

Note: You change the Description, User, and ExecStart fields suitable for your application.

Start the service:

$ sudo systemctl start myapp

Check the status is active

$ sudo systemctl status myapp

Spring Boot and System V

Create a specific user to run the service and executable JAR file.

$ cd /opt/myapp
$ sudo useradd huupv
$ sudo passwd huupv
$ sudo chown huupv:huupv myapp.jar
$ sudo chmod 500 myapp.jar

Assuming you have a Spring Boot application installed in the folder /opt/myapp . you need to create a symlink as follows:

$ sudo ln -s /opt/myapp/myapp.jar /etc/init.d/myapp

Start the service

$ sudo service myapp start

You have created the “Spring Boot application as a service in Linux“.Thank you for reading the DevopsRoles page!