Linux Redhat version 6.3
There is Commands,,,
.
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
2.
grep command examples
Search for a given string in a file (case
in-sensitive search).
$ grep -i "the" demo_file
Print the
matched line, along with the 3 lines after it.
$ grep -A 3 -i "example" demo_text
Search for a
given string in all files recursively
$ grep -r "ramesh" *
More grep
examples: Get
a Grip on the Grep! – 15 Practical Grep Command Examples
3. find command examples
Find files
using file-name ( case in-sensitve find)
# find -iname "MyCProgram.c"
Execute
commands on files found by the find command
$ find -iname "MyCProgram.c" -exec md5sum {} \;
Find all
empty files in home directory
# find ~ -empty
More find
examples: Mommy,
I found it! — 15 Practical Linux Find Command Examples
4. ssh command examples
Login to
remote host
ssh -l jsmith remotehost.example.com
Debug ssh
client
ssh -v -l jsmith remotehost.example.com
Display ssh
client version
$ ssh -V
OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003
More ssh
examples: 5
Basic Linux SSH Client Commands
5. sed command examples
When you
copy a DOS file to Unix, you could find \r\n in the end of each line. This
example converts the DOS file format to Unix file format using sed command.
$sed 's/.$//' filename
Print file
content in reverse order
$ sed -n '1!G;h;$p' thegeekstuff.txt
Add line
number for all non-empty-lines in a file
$ sed '/./=' thegeekstuff.txt | sed 'N; s/\n/ /'
More sed
examples: Advanced
Sed Substitution Examples
6. awk command examples
Remove
duplicate lines using awk
$ awk '!($0 in array) { array[$0]; print }' temp
Print all
lines from /etc/passwd that has the same uid and gid
$awk -F ':' '$3==$4' passwd.txt
Print only
specific field from a file.
$ awk '{print $2,$5;}' employee.txt
More awk
examples: 8
Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR
7. vim command examples
Go to the
143rd line of file
$ vim +143 filename.txt
Go to the
first match of the specified
$ vim +/search-term filename.txt
Open the
file in read only mode.
$ vim -R /etc/passwd
More vim
examples: How
To Record and Play in Vim Editor
8. diff command examples
Ignore white
space while comparing.
# diff -w name_list.txt name_list_new.txt
2c2,3
< John Doe --- > John M Doe
> Jason Bourne
More diff
examples: Top 4
File Difference Tools on UNIX / Linux – Diff, Colordiff, Wdiff, Vimdiff
9. sort command examples
Sort a file
in ascending order
$ sort names.txt
Sort a file
in descending order
$ sort -r names.txt
Sort passwd
file by 3rd field.
$ sort -t: -k 3n /etc/passwd | more
10. export command examples
To view
oracle related environment variables.
$ export | grep ORACLE
declare -x ORACLE_BASE="/u01/app/oracle"
declare -x
ORACLE_HOME="/u01/app/oracle/product/10.2.0"
declare -x ORACLE_SID="med"
declare -x ORACLE_TERM="xterm"
To export an
environment variable:
$ export ORACLE_HOME=/u01/app/oracle/product/10.2.0
11. xargs command examples
Copy all
images to external hard-drive
# ls *.jpg | xargs -n1 -i cp {}
/external-hard-drive/directory
Search all
jpg images in the system and archive it.
# find / -name *.jpg -type f -print | xargs tar -cvzf
images.tar.gz
Download all
the URLs mentioned in the url-list.txt file
# cat url-list.txt | xargs wget –c
12. ls command examples
Display
filesize in human readable format (e.g. KB, MB etc.,)
$ ls -lh
-rw-r----- 1 ramesh team-dev 8.9M Jun 12 15:27
arch-linux.txt.gz
Order Files
Based on Last Modified Time (In Reverse Order) Using ls -ltr
$ ls -ltr
Visual
Classification of Files With Special Characters Using ls -F
$ ls -F
More ls
examples: Unix LS
Command: 15 Practical Examples
13. pwd command
pwd is Print
working directory. What else can be said about the good old pwd who has been
printing the current directory name for ages.
14. cd command examples
Use “cd -”
to toggle between the last two directories
Use “shopt
-s cdspell” to automatically correct mistyped directory names on cd
More cd
examples: 6
Awesome Linux cd command Hacks
15. gzip command examples
To create a
*.gz compressed file:
$ gzip test.txt
To
uncompress a *.gz file:
$ gzip -d test.txt.gz
Display
compression ratio of the compressed file using gzip -l
$ gzip -l *.gz
compressed
uncompressed ratio uncompressed_name
23709 97975 75.8% asp-patch-rpms.txt
16. bzip2 command examples
To create a
*.bz2 compressed file:
$ bzip2 test.txt
To
uncompress a *.bz2 file:
bzip2 -d test.txt.bz2
More bzip2
examples: BZ
is Eazy! bzip2, bzgrep, bzcmp, bzdiff, bzcat, bzless, bzmore examples
17. unzip command examples
To extract a
*.zip compressed file:
$ unzip test.zip
View the
contents of *.zip file (Without unzipping it):
$ unzip -l jasper.zip
Archive: jasper.zip
Length Date
Time Name
-------- ----
---- ----
40995 11-30-98 23:50 META-INF/MANIFEST.MF
32169 08-25-98 21:07 classes_
15964 08-25-98 21:07 classes_names
10542 08-25-98 21:07 classes_ncomp
18. shutdown command examples
Shutdown the
system and turn the power off immediately.
# shutdown -h now
Shutdown the
system after 10 minutes.
# shutdown -h +10
Reboot the
system using shutdown command.
# shutdown -r now
Force the
filesystem check during reboot.
# shutdown -Fr now
19. ftp command examples
Both ftp and
secure ftp (sftp) has similar commands. To connect to a remote server and
download multiple files, do the following.
$ ftp IP/hostname
ftp> mget *.html
To view the
file names located on the remote server before downloading, mls ftp command as
shown below.
ftp> mls *.html -
/ftptest/features.html
/ftptest/index.html
/ftptest/othertools.html
/ftptest/samplereport.html
/ftptest/usage.html
More ftp
examples: FTP
and SFTP Beginners Guide with 10 Examples
20. crontab command examples
View crontab
entry for a specific user
# crontab -u john -l
Schedule a
cron job every 10 minutes.
*/10 * * * * /home/ramesh/check-disk-space
More crontab
examples: Linux
Crontab: 15 Awesome Cron Job Examples
21. service command examples
Service
command is used to run the system V init scripts. i.e Instead of calling the
scripts located in the /etc/init.d/ directory with their full path, you can use
the service command.
Check the
status of a service:
# service ssh status
Check the
status of all the services.
service --status-all
Restart a
service.
# service ssh restart
22. ps command examples
ps command
is used to display information about the processes that are running in the
system.
While there
are lot of arguments that could be passed to a ps command, following are some
of the common ones.
To view
current running processes.
$ ps -ef | more
To view
current running processes in a tree structure. H option stands for process
hierarchy.
$ ps -efH | more
23. free command examples
This command
is used to display the free, used, swap memory available in the system.
Typical free
command output. The output is displayed in bytes.
$ free
total used free
shared buffers cached
Mem: 3566408 1580220
1986188 0 203988
902960
-/+ buffers/cache:
473272 3093136
Swap: 4000176 0
4000176
If you want
to quickly check how many GB of RAM your system has use the -g option. -b
option displays in bytes, -k in kilo bytes, -m in mega bytes.
$ free -g
total used free
shared buffers cached
Mem: 3 1 1 0 0 0
-/+ buffers/cache:
0 2
Swap: 3 0 3
If you want
to see a total memory ( including the swap), use the -t switch, which will
display a total line as shown below.
ramesh@ramesh-laptop:~$ free -t
total used free
shared buffers cached
Mem: 3566408 1592148
1974260 0 204260
912556
-/+ buffers/cache:
475332 3091076
Swap: 4000176 0
4000176
Total: 7566584 1592148
5974436
24. top command examples
top command
displays the top processes in the system ( by default sorted by cpu usage ). To
sort top output by any column, Press O (upper-case O) , which will display all
the possible columns that you can sort by as shown below.
Current Sort Field:
P for window 1:Def
Select sort field via field letter, type any other key to
return
a: PID = Process Id v: nDRT = Dirty Pages count
d: UID = User Id y: WCHAN = Sleeping in Function
e: USER = User Name z: Flags = Task Flags
........
To displays
only the processes that belong to a particular user use -u option. The
following will show only the top processes that belongs to oracle user.
$ top -u oracle
More top
examples: Can
You Top This? 15 Practical Linux Top Command Examples
25. df command examples
Displays the
file system disk space usage. By default df -k displays output in bytes.
$ df -k
Filesystem
1K-blocks Used Available Use%
Mounted on
/dev/sda1
29530400 3233104 24797232
12% /
/dev/sda2
120367992 50171596 64082060
44% /home
df -h
displays output in human readable form. i.e size will be displayed in GB’s.
ramesh@ramesh-laptop:~$ df -h
Filesystem
Size Used Avail Use% Mounted on
/dev/sda1
29G 3.1G 24G
12% /
/dev/sda2
115G 48G 62G
44% /home
Use -T
option to display what type of file system.
ramesh@ramesh-laptop:~$ df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/sda1 ext4 29530400
3233120 24797216 12% /
/dev/sda2 ext4 120367992
50171596 64082060 44% /home
26. kill command examples
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.
$ ps -ef | grep vim
ramesh 7243 7222 9
22:43 pts/2 00:00:00 vim
$ kill -9 7243
More kill
examples: 4
Ways to Kill a Process – kill, killall, pkill, xkill
27. rm command examples
Get
confirmation before removing the file.
$ rm -i filename.txt
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
28. cp command examples
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
29. 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
30. 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.
$ cat -n /etc/logrotate.conf
1 /var/log/btmp {
2
missingok
3
monthly
4
create 0660 root utmp
5
rotate 1
6 }
31. mount command examples
To mount a
file system, you should first create a directory and mount it as shown below.
# mkdir /u01
# mount /dev/sdb1 /u01
You can also
add this to the fstab for automatic mounting. i.e Anytime system is restarted,
the filesystem will be mounted.
/dev/sdb1 /u01 ext2 defaults 0 2
32. 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 specific file.
$ chmod ug+rwx file.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
More chmod
examples: 7
Chmod Command Examples for Beginners
33. chown command examples
chown
command is used to change the owner and group of a file. \
To change
owner to oracle and group to db on a file. i.e Change both owner and group at
the same time.
$ chown oracle:dba dbora.sh
Use -R to
change the ownership recursively.
$ chown -R oracle:dba /home/oracle
34. passwd command examples
Change your
password from command line using passwd. This will prompt for the old password
followed by the new password.
$ passwd
Super user
can use passwd command to reset others password. This will not prompt for
current password of the 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
35. mkdir command examples
Following
example creates a directory called temp under your home directory.
$ mkdir ~/temp
Create
nested directories using one mkdir command. If any of these directories exist
already, it will not display any error. If any of these directories doesn’t
exist, it will create them.
$ mkdir -p dir1/dir2/dir3/dir4/
36. ifconfig command examples
Use ifconfig
command to view or configure a network interface on the Linux system.
View all the
interfaces along with status.
$ ifconfig -a
Start or
stop a specific interface using up and down command as shown below.
$ ifconfig eth0 up
$ ifconfig eth0 down
More
ifconfig examples: Ifconfig:
7 Examples To Configure Network Interface
37. uname command examples
Uname
command displays important information about the system such as — Kernel name,
Host name, Kernel release number,
Processor type, etc.,
Processor type, etc.,
Sample uname
output from a Ubuntu laptop is shown below.
$ uname -a
Linux john-laptop 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19
01:12:52 UTC 2010 i686 GNU/Linux
38. whereis command examples
When you
want to find out where a specific Unix command exists (for example, where does
ls command exists?), you can execute the following command.
$ whereis ls
ls: /bin/ls /usr/share/man/man1/ls.1.gz
/usr/share/man/man1p/ls.1p.gz
When you
want to search an executable from a path other than the whereis default path,
you can use -B option and give path as argument to it. This searches for the
executable lsmk in the /tmp directory, and displays it, if it is available.
$ whereis -u -B /tmp -f lsmk
lsmk: /tmp/lsmk
39. whatis command examples
Whatis
command displays a single line description about a command.
$ whatis ls
ls (1) - list directory contents
$ whatis ifconfig
ifconfig (8) -
configure a network interface
40. locate command examples
Using locate
command you can quickly search for the location of a specific file (or group of
files). Locate command uses the database created by updatedb.
The example
below shows all files in the system that contains the word crontab in it.
$ locate crontab
/etc/anacrontab
/etc/crontab
/usr/bin/crontab
/usr/share/doc/cron/examples/crontab2english.pl.gz
/usr/share/man/man1/crontab.1.gz
/usr/share/man/man5/anacrontab.5.gz
/usr/share/man/man5/crontab.5.gz
/usr/share/vim/vim72/syntax/crontab.vim
41. man command examples
Display the
man page of a specific command.
$ man crontab
When a man
page for a command is located under more than one section, you can view the man
page for that command from a specific section as shown below.
$ man SECTION-NUMBER commandname
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
- Miscellaneous
- System administration commands
and daemons
For example,
when you do whatis crontab, you’ll notice that crontab has two man pages
(section 1 and section 5). To view section 5 of crontab man page, do the
following.
$ whatis crontab
crontab (1) -
maintain crontab files for individual users (V3)
crontab (5) -
tables for driving cron
$ man 5 crontab
42. 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
View the
content of the file in real time using tail -f. This is useful to view the log
files, that keeps growing. The command can be terminated using CTRL-C.
$ tail -f log-file
More tail
examples: 3
Methods To View tail -f output of Multiple Log Files in One Terminal
43. less command examples
less is very
efficient while viewing huge log files, as it doesn’t need to load the full
file while opening.
$ less huge-log-file.log
One you open
a file using less command, following two keys are very helpful.
CTRL+F – forward one window
CTRL+B – backward one window
More less
examples: Unix
Less Command: 10 Tips for Effective Navigation
44. 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
Execute a
single command from a different account name. In the following example, john
can execute the ls command as raj username. Once the command is executed, it
will come back to john’s account.
[john@dev-server]$ su - raj -c 'ls'
[john@dev-server]$
Login to a
specified user account, and execute the specified shell instead of the default
shell.
$ su -s 'SHELLNAME' USERNAME
45. mysql command examples
mysql is
probably the most widely used open source database on Linux. Even if you don’t
run a mysql database on your server, you might end-up using the mysql command (
client ) to connect to a mysql database running on the remote server.
To connect
to a remote mysql database. This will prompt for a password.
$ mysql -u root -p -h 192.168.1.2
To connect
to a local mysql database.
$ mysql -u root -p
If you want
to specify the mysql root password in the command line itself, enter it
immediately after -p (without any space).
46. yum command examples
To install
apache using yum.
$ yum install httpd
To upgrade
apache using yum.
$ yum update httpd
To
uninstall/remove apache using yum.
$ yum remove httpd
47. rpm command examples
To install
apache using rpm.
# rpm -ivh httpd-2.2.3-22.0.1.el5.i386.rpm
To upgrade
apache using rpm.
# rpm -uvh httpd-2.2.3-22.0.1.el5.i386.rpm
To
uninstall/remove apache using rpm.
# rpm -ev httpd
More rpm
examples: RPM
Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Packages
48. ping command examples
Ping a
remote host by sending only 5 packets.
$ ping -c 5 gmail.com
More ping
examples: Ping
Tutorial: 15 Effective Ping Command Examples
49. date command examples
Set the
system date:
# date -s "01/31/2010 23:59:53"
Once you’ve
changed the system date, you should syncronize the hardware clock with the
system date as shown below.
# hwclock –systohc
# hwclock --systohc –utc
50. wget command examples
The quick
and effective method to download software, music, video from internet is using
wget command.
Download and
store it with a different name.
$ wget -O taglist.zip
http://www.vim.org/scripts/download_script.php?src_id=7701
More wget
examples: The
Ultimate Wget Download Guide With 15 Awesome Examples
Did I miss
any frequently used Linux commands? Leave a comment and let me know.
----------------------------------------------------------------------------------------------------------------------
More commands ....
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Command
|
Description
|
1. logname
|
Current user name
|
2. pwd
|
Present working directory
|
3. uname
|
Display kernel name
|
4. uname -n
|
Print network hostname
|
5. uname -r
|
Display kernel version
|
6. uname -v
|
Display kernel release date
|
7. uname -i
|
Print hardware platform
|
8. uname -o
|
Print the operating system
|
9. uname -p
|
Print the processser name
|
10. uname -a
|
Print all information
|
11. date
|
Display system date and time
|
12. clear
|
To clear the screen
|
13. cal
|
Display current month calendar
|
14. cal 2014
|
Display 2014 calendar
|
15. cal 9 1987
|
Displays the September 1987 calendar
|
16. bc
|
Open calculator
|
17. bc -v
|
Version of calculator
|
18. hostname
|
Display server name
|
19. hostname -i
|
Display server IP address
|
20. tty
|
Display terminal name
|
21. who
|
To display how many users connected to server
|
22. whoami
|
Display current username
|
23. uptime
|
Display how long server is “up &running”, no. Of users connected &avg load on the server.
|
24. which <command name>
|
Show the full path of command
|
25. whereis <command name>
|
Display the binary, source, and manual page files for a command
|
26. find
|
Search for files in a directory hierarchy
|
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