10 Most Frequently Used Linux/UNIX Commands

Hi everyone, today I’m posting a list of most frequently used linux commands that I use.

1.ls command

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

2.sort command 

Sort a file in ascending order

$ sort file.txt

Sort a file in descending order

$ sort -r file.txt

3.grep command 
Search for a given string in a file (case in-sensitive search).

$ grep -i "the" example_file

Print the matched line, along with the 5 lines after it.

$ grep -A 5 -i "example" example_text

Search for a given string in all files recursively

$ grep -r "Sam" *

4. find command

Find files using file-name ( case in-sensitve find)

# find -iname "HelloWorld.c"

Execute commands on files found by the find command

$ find -iname "MyCProgram.c" -exec md5sum {} \;

5.ssh command

Login to remote host

ssh -l ramu remotehost.example.com

Debug ssh client

ssh -v -l ramu remotehost.example.com

6.vim command

Go to the 100th line of file

$ vim +100 filename.txt

Go to the first match of the specified

$ vim +/search-term my_file.txt

Open the file in read only mode.

$ vim -R /etc/oratab

7. export command

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"

8.gzip command

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

9.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

10.ftp command

To connect to a remote server and download multiple files.

$ 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 -

/test/hello.html

/test/employees.html

/test/tools.html

/test/sampletest.html

/test/users.html