Linux Commands Every User Should Know
Before we go on to the list of commands, you need to open the command line first, so in this post, I will use "Git Bash" which is an application for Microsoft Windows OS environments that provides Unix-based shell utilities & experience for Git command-line commands.
Here is a list of basic Linux commands:
cd command Use the cd command to navigate through Linux files and directories. Depending on the current working directory, it requires either the full path or the name of the directory.
cd .. (with two dots) to move one directory up
cd to go straight to the home folder
cd- (with a hyphen) to move to your previous directory
cd / - Return to Root Directory
whoami command
The whoami command displays the effective user ID's user name. In other words, it shows the name of the user who is currently logged in.
[vagrant@localhost ~]$ whoami
vagrant
pwd command The location of your current working directory (folder). The command returns an absolute (full) path, which is a list of all directories that begin with a forward slash (/).
[vagrant@localhost ~]$ pwd
/home/vagrantls command List all directories and files using, You can use the ls command in a variety of ways:
ls -R will list all the files in the sub-directories as well
ls -a will show the hidden files
ls -al will list the files and directories with detailed information like the permissions, size, owner, etc.
David@DESKTOP-VIK2BBH MINGW64 ~
$ ls
'3D Objects'/
AppData/
'Application Data'@
Contacts/
Cookies@David@DESKTOP-VIK2BBH MINGW64 ~
$ ls -al
total 7489
drwxr-xr-x 1 David 197121 0 May 25 19:54 ./
drwxr-xr-x 1 David 197121 0 Mar 14 2021 ../
drwxr-xr-x 1 David 197121 0 May 26 12:19 .VirtualBox/
-rw-r--r-- 1 David 197121 2431 May 26 14:24 .bash_history
drwxr-xr-x 1 David 197121 0 Nov 11 2021 .docker/mkdir command
Use mkdir command to make a new directory use mkdir command to make a new directory
To generate a new directory inside another directory, use this Linux basic command mkdir FolderA/FolderC
Use the p (parents) option to create a directory in between two existing directories. For example, mkdir -p FolderA / FolderB / FolderC.
David@DESKTOP-VIK2BBH MINGW64 /c/folderA/folderB/folderC
$ pwd
/c/folderA/folderB/folderCcat command
It is used to list the contents of a file on the standard output. To run this command, type cat followed by the file’s name and its extension.
[root@localhost ~]# cat /etc/os-release
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
touch command
You can use the touch command to create a new file from the Linux command line.
We can also use this command to create multiple files using {}, for instance:
[root@localhost /]# mkdir devops
[root@localhost /]# cd devops
[root@localhost devops]# touch testfile{1..15}.txt
[root@localhost devops]# ls
testfile10.txt testfile12.txt testfile14.txt testfile1.txt testfile3.txt testfile5.txt testfile7.txt testfile9.txt
testfile11.txt testfile13.txt testfile15.txt testfile2.txt testfile4.txt testfile6.txt testfile8.txt
[root@localhost devops]#mv command
The mv command is primarily used to move files, but it can also be used to rename them.
You need to type mv, the file’s name, and the destination’s directory. For example: mv file.txt /root/FolderA
To rename files, the command is mv oldfilename.ext newdilename.ext
Example 1: Rename FIle
David@DESKTOP-VIK2BBH MINGW64 /c/filesexample
$ ls
creatingsinglefile.txt file2.txt file3.txt file4.txt
David@DESKTOP-VIK2BBH MINGW64 /c/filesexample
$ mv file2.txt newfilename.txt
David@DESKTOP-VIK2BBH MINGW64 /c/filesexample
$ ls
creatingsinglefile.txt file3.txt file4.txt newfilename.txt
David@DESKTOP-VIK2BBH MINGW64 /c/filesexample
$Example 2: Move file
root@localhost ~]# cd /
[root@localhost /]# ls
bin dev home lib64 mnt proc run srv tmp vagrant
boot etc lib media opt root sbin sys usr var
[root@localhost /]# pwd
/
[root@localhost /]# mkdir folderA folderB
[root@localhost /]# ls
bin dev folderA home lib64 mnt proc run srv tmp vagrant
boot etc folderB lib media opt root sbin sys usr var
[root@localhost /]# touch folderA/file.txt
[root@localhost /]# cd folderA
[root@localhost folderA]# ls
file.txt
[root@localhost folderA]# mv file.txt /folderB
[root@localhost folderA]# ls
[root@localhost folderA]# cd ..
[root@localhost /]# cd folderB
[root@localhost folderB]# ls
file.txtcp command
Use the cp command to copy files from the current directory to a different directory.
[root@localhost folderB]# ls
file.txt newfile.txt
[root@localhost folderB]# cp file.txt /folderA
[root@localhost folderB]# ls
file.txt newfile.txt
[root@localhost folderB]# cd ..
[root@localhost /]# ls
bin dev folderA home lib64 mnt proc run srv tmp vagrant
boot etc folderB lib media opt root sbin sys usr var
[root@localhost /]# cd folderA
[root@localhost folderA]# ls
file.txt newfile.txt
[root@localhost folderA]#rmdir command
The rmdir command can be used to delete a directory. rmdir, on the other hand, can only be used to delete empty directories.
Locate command
This command, like the search command in Windows, can be used to locate a file. Furthermore, if you use the -I argument with this command, it will search for files regardless of the case, allowing you to find a file even if you don't remember its exact name.
To search for a file that contains two or more words, use an asterisk (*)
For example, locate -i AAA*BBB command will search for any file that contains the word “AAA” and “BBB”, whether it is uppercase or lowercase.
if `you are using Centos, you will first need to install "locate":
Step 1: run: sudo yum install mlocate
Steo 2: run sudo updated
Examples:
[root@localhost folderA]# locate -i file.txt
/folderA/file.txt
/folderA/newfile.txt
/folderB/file.txt
/folderB/newfile.txt
[root@localhost folderA]#we can use '.' prior to our string, it will return all files with the specified file names
[root@localhost folderA]# locate .sys
/etc/dbus-1/system.d/org.freedesktop.systemd1.conf
/usr/lib/firmware/slicoss/gbdownload.sys
/usr/lib/firmware/slicoss/gbrcvucode.sys
/usr/lib/firmware/slicoss/oasisdbgdownload.sys
/usr/lib/firmware/slicoss/oasisdownload.sysfind command
Find, like the locate command, searches for files and directories. The find command, on the other hand, is used to locate files within a given directory.
Example 1: Find all files in a folder
[root@localhost folderA]# find
.
./newfile.txt
./file.txt
[root@localhost folderA]#Example 2: Find a specific file
[root@localhost folderA]# find -name newfile.txt
./newfile.txtgrep command
Grep is another basic Linux command that is unquestionably useful for everyday use. It allows you to search all of the text in a given file. For example, grep aa notepad.txt will look for the word aa in the notepad file. Lines containing the searched word will be displayed in their entirety.
Options:
Options Description-c : This prints only a count of the lines that match a pattern
-h : Display the matched lines, but do not display the filenames.
-i : Ignores, case for matching
-l : Displays list of a filenames only.
-n : Display the matched lines and their line numbers.
-v : This prints out all the lines that do not matches the pattern
-e exp : Specifies expression with this option. Can use multiple times.
-f file : Takes patterns from file, one per line.
-E : Treats pattern as an extended regular expression (ERE)
-w : Match whole word
-o : Print only the matched parts of a matching line,
Credit: https://www.geeksforgeeks.org/grep-command-in-unixlinux/Example :
David@DESKTOP-VIK2BBH MINGW64 /c/filesearch
$ ls
Grep.txt
David@DESKTOP-VIK2BBH MINGW64 /c/filesearch
$ cat grep.txt
A “Timebox” is an agreed and limited period used by a
person/team to perform a dedicated activity.
Once the Timebox is approved and set, the team
/person works to complete a goal within this t
ime. If the time ended without completing all
the activities required, then how to continue
will depend on the time-box approach (Soft Vs. Hard).
grep is a command-line uti
lity for searching plain-text data sets
for lines that match a regular expression.
Its name comes from the ed command g/re/p, whic
h has the same effect. grep was originally developed for the Unix o
perating system, but later available fo
r all Unix-like systems and some others such as OS-9.
David@DESKTOP-VIK2BBH MINGW64 /c/filesearch
$ grep effect grep.txt
h has the same effect. grep was originally developed for the Unix o
David@DESKTOP-VIK2BBH MINGW64 /c/filesearchhead command
The head command displays the first lines of any text file. It will display the first ten lines by default, but you can change this number to your personal preferences.
tail command
The tail command performs a similar function to the head command, but instead of displaying the first ten lines of a text file, it displays the last ten lines.
diff command
The diff command, which stands for difference, compares the contents of two files line by line. It will output the lines that do not match after analyzing the files. (The most basic version of this command is diff file1.ext file2.ext).
sudo command
This command allows you to carry out tasks that require administrative or root privileges. However, it is not recommended to use this command on a regular basis because it is easy for an error to occur if something goes wrong.
➔ sudo -i changes from normal user to root user
David@DESKTOP-VIK2BBH MINGW64 /c/vagrant-training/centosexample
$ vagrant ssh
Last login: Thu May 26 15:22:52 2022 from 10.0.2.2
[vagrant@localhost ~]$ whoami
vagrant
[vagrant@localhost ~]$ sudo -i
[root@localhost ~]# whoami
root
[root@localhost ~]#df command
To get a report on the system's disk space usage in percentages and KBs, use the df command. Type df -m to display the report in megabytes.
jobs command
The jobs command displays all current jobs and their statuses. A job is essentially a process that the shell initiates.
ping command
To check your server connectivity, use the ping command. For example, simply typing ping google.com will check whether you can connect to Google and also measure the response time.
[root@localhost /]# ping www.google.com
PING www.google.com (142.250.185.68) 56(84) bytes of data.
64 bytes from fra16s48-in-f4.1e100.net (142.250.185.68): icmp_seq=1 ttl=112 time=79.1 ms