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Useful Commands For Unix Operating System

Useful Commands For Unix Operating System


1.Deleting files older than N number of days ?

find . -name ‘*.trc’ -mtime +[N in days]  -exec rm {} \;  
Command will delete files older then N days in that directory


2.Copying file keeping timestamp preserve

cp -ip file.txt file_txt_bkp


3.Listing files modified in last N days

find . -mtime -<ndays> -exec ls -lt {} \;


4.Sorting files based on Size of file ? 

ls -l | sort -nrk 5  | more
du -sm *|sort -nr|head -10 


5.Finding CPU & Memory detail 

->cat /proc/cpuinfo  (CPU)
->cat /proc/meminfo (Memory)


6.Finding if any service is listening on particular port or not ?

netstat -an | grep {port no}  


7.Finding Process ID (PID) associated with any port ?

lsof | grep {port no.}  
lsof should be installed and in path.Many times it will be installed eith root user.Make sure you have that permission


9.Finding a pattern in some file in a directory ?

grep pattern  file_name  ( find pattern in particular file )
grep -i pattern  file_name (find pattern ignoring the case)


10.Create symbolic link to a file ?

ln -s  pointing_to_original_file  symbolic_link_name

 ln -s /home/text.txt test.txt


11.History of command executed in UNIX 

fc -l 
fc -e – ls ( Would execute the last ls command.) 
History command will also do the same


12. Compressing a big file

zip -r new.zip new
compress file_name


13.Creating a tar file

tar -cvwf file.tar file.txt


14.Extracting the files from a tar file

tar -xvwf myfile.tar(System would unarchive (untar) the myfile.tar file into the current directory.)
tar -xvwzf myfile.tar.gz(System would unarchive (untar) the myfile.tar.gz file in the current directory.)


14.Extracting a gz file?

Use guzip command as follows:
gunzip file.gz
gzip -d file.gz


15.Extract a tar.gz or .tgz file?

Files with extension tar.gz or .tgz are tar files compressed with gzip. On Unix system extract them with following command:
gunzip < file.tar.gz | tar xvf –
gunzip < file.tgz | tar xvf –

If you have GNU tar (Linux system) you can use the z option directly:
tar xvzf file.tar.gz
tar xvzf file.tgz


16.Using mailx command

echo “This is going to be body of the mail” |mailx -s “Subject:Testing” “false@gmail.com”


17.Checking the file system free and used space

df -gt 



About Syed Saad Ali

As a certified and experienced Oracle Database Administrator with Almost 10 Years of Experience I am able to perform all levels of database maintenance and am fully qualified to do Oracle updates as well. Capitalizing on my interest in Business & IT both, I chose to navigate my career towards Enterprise Solutions, which has enabled me to excel in the combination of both. I have developed exceptional analytical skills that allow me to diagnose and take care of issues immediately. Extremely skilled in planning and execution of special projects in time- critical environments. Extensive knowledge in directing, coordinating and exercising concern authority for planning, organization, control and successful completions. Very skilled at solving customer relations issues by seeking first to understand and then to be understood. Effectively able to communicate with customers, vendors and management.

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