tar command examples
Create a new tar archive.
$ tar cvf archive_name.tar dirname/
Extract from an existing tar archive.
$ tar xvf archive_name.tar
View an existing tar archive.
$ tar tvf archive_name.tar
grep command examples
search a string pattern in the given file.
search a string pattern in the given file (case insensitive).
print the matched line and along with the 3 line after that word
Search for a given string in all files recursively.
find command examples
Limit depth of directory traversal
The following command searches for files by their name in that specified directory.
We can also find file or directory with wild charecter.
vim command examples
Go to the 3rd line of file
$ vim +3 filename.txt
Go to the first match of the specified
$ vim +/search-term filename.txt
Open the file in read only mode.
$ vim -R file_name
diff command examples
diff command check the difference between the two file that we given and also it will Ignore white space while comparing.
sort command examples
Sort the file content in ascending order
Sort the file content in descending order
ls command examples
Display filesize in human readable format (e.g. KB, MB etc.,)
$ ls -lh
anusree@anusree-Inspiron-5547:~/anusree$ ls -lh
-rw-rw-r-- 1 anusree anusree 117 Apr 14 15:26 anureesaju.tar.gz
drwxrwxr-x 4 anusree anusree 4.0K May 7 08:23 anusaju
-rw-rw-r-- 1 anusree anusree 22 Mar 16 12:11 anu.txt
-rw-rw-r-- 1 anusree anusree 0 Mar 16 12:11 anu.txt~
-rw-rw-r-- 1 anusree anusree 171 Feb 23 01:30 django_notes
drwxrwxr-x 4 anusree anusree 4.0K Apr 6 22:48 extra
Order Files Based on Last Modified Time (In Reverse Order) Using ls -ltr
$ ls -ltr
anusree@anusree-Inspiron-5547:~/anusree$ ls -ltr
-rw------- 1 anusree anusree 250 Feb 15 12:22 pay_hr_rt.py
-rw------- 1 anusree anusree 319 Feb 15 12:32 pay_tryex.py
-rw------- 1 anusree anusree 133 Feb 20 13:11 fibb.py
-rw-r--r-- 1 anusree anusree 20 Feb 21 10:02 hello.py
-rw-rw-r-- 1 anusree anusree 321 Feb 21 20:47 looping_tec.py
drwxrwxr-x 6 anusree anusree 4096 Feb 23 00:40 venv
-rw-rw-r-- 1 anusree anusree 0 Feb 23 01:24 Untitled Document~
pwd is Print working directory.
cd command examples
Use “cd -” to toggle between the last two directories
shutdown command examples
Shutdown the system and turn the power off immediately It need the administration power.
$ sudo shutdown -h now
Shutdown the system after 10 minutes.
$ sudo shutdown -h +10
Reboot the system using shutdown command.
$ shutdown -r now
ps command example
ps command is used to display information about the processes that are running in the system..
To view current running processes.
$ ps -ef
free command example
This command is used to display the free, used, swap memory available in the system.
Display the amount of memory in bytes.
Display the amount of memory in kilobytes. This is the default.
Display the amount of memory in megabytes.
Display the amount of memory in gigabytes.
--tera Display the amount of memory in terabytes.
Show all output fields automatically scaled to shortest three digit unit and display the units of print out. Following units are used.
B = bytes
K = kilos
M = megas
G = gigas
T = teras
top command example
The top program provides a dynamic real-time view of a running system.
$ top -h -----> Show library version and the usage prompt, then quit.
df command examples
Displays the file system disk space usage. By default df -k displays output in bytes.
list inode information instead of block usage
print sizes in human readable format (e.g., 1K 234M 2G)
kill command example:
Use kill command to terminate a process. First get the process id using ps -ef command, then use kill -9 to kill the running Linux process as shown below. You can also use killall, pkill, xkill to terminate a unix process.
$ kill process_id
rm command examples:
remove files or directories
Get confirmation before removing the file.
$ rm -i filename
It is very useful while giving shell metacharacters in the file name argument.
Print the filename and get confirmation before removing the file.
$ rm -i file*
Following example recursively removes all files and directories under the example directory. This also removes the example directory itself.
$ rm -r example
cp command examples
copy files and directories
Copy file1 to file2 preserving the mode, ownership and timestamp.
$ cp -p file1 file2
Copy file1 to file2. if file2 exists prompt for confirmation before overwritting it.
$ cp -i file1 file2
mv command examples
Rename file1 to file2. if file2 exists prompt for confirmation before overwritting it.
$ mv -i file1 file2
Note: mv -f is just the opposite, which will overwrite file2 without prompting.
mv -v will print what is happening during file rename, which is useful while specifying shell metacharacters in the file name argument.
$ mv -v file1 file2
cat command examples
You can view multiple files at the same time. Following example prints the content of file1 followed by file2 to stdout.
$ cat file1 file2
While displaying the file, following cat -n command will prepend the line number to each line of the output.
chmod command examples
chmod command is used to change the permissions for a file or directory.
Give full access to user and group (i.e read, write and execute ) on a more than one file.
$ chmod ug+rwx file.txt file2.txt
Revoke all access for the group (i.e read, write and execute ) on a specific file.
$ chmod g-rwx file.txt
Apply the file permissions recursively to all the files in the sub-directories.
$ chmod -R ug+rwx file.txt
passwd command examples
Change your password from command line using passwd. This will prompt for the old password followed by the new password. If you only type the command passwd without any options the the password of root user will changed
To change the password for a particular user
$ passwd USERNAME
Remove password for a specific user. Root user can disable password for a specific user. Once the password is disabled, the user can login without entering the password.
$ passwd -d USERNAME
uname command examples
Uname command displays important information about the system such as — Kernel name, Host name, Kernel release number,
Processor type, etc.,
Sample uname output from a Ubuntu laptop is shown below.
If you want to know all the information about system the type the option -a
whereis command examples
When you want to find out where a specific Unix command exists
for example, where does ls command and cat command exists?
whatis command examples
Whatis command displays a single line description about a command.
Display the man page of specific command
Following 8 sections are available in the man page.
- General commands
- System calls
- C library functions
- Special files (usually devices, those found in /dev) and drivers
- File formats and conventions
- Games and screensavers
- System administration commands and daemons
tail command examples
Print the last 10 lines of a file by default.
$ tail filename.txt
Print N number of lines from the file named filename.txt
$ tail -n N filename.txt
su command examples
Switch to a different user account using su command. Super user can switch to any other user without entering their password.
$ su - USERNAME
mysql command example
mysql is a simple SQL shell with input line editing capabilities. It supports interactive and noninteractive use. When used interactively
To connect a local msql database
$ mysql -u root -p
date command example
print or set the system date and time
If you want to know a particular day in the paricular date
wget command examples
The quick and effective method to download software, music, video from internet is using wget command
$ wget link-for-download-the-file