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)
->topas
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
example
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
history
12. Compressing a big file
zip -r new.zip new
or
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
OR
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