Linux Commands used in Terminal

ls -list the files and directories.
cd -change the diretory
cd/ - the folder comes to the root
cal - show calendar
mkdir directory name - create directory
rmdir directory name - remove directory
cat > file name - create file
ctrl +z - stop and save data
cat file name - show the data file
cat >> file name - append data in file
pwd - present / print working directory
who - display information about all user on system
whoami -Tells the name of user currently logged in
man - Provides manual data about any file or command
wc - display the no. of lines words , and characters in that files and also tell the name of file
banner - It displays the massage in large size
ls- l file name - prints authorization for each file
chmod - chamnge the permisson
date - display the date
grep - searches a particular content
grep -c - count tne no. of tatal lines
grep -n - display line no. in which the content is present
adduser - create user
hostname - print the name of local host
last - show listing of user logged in on computer
free - check memory status
uname - print system information
man - for help
date -show date
ls -l - list of file and directory
sudo init 0 -shutdown computer
sudo init 6 - restart computer
clear - clear terminal screen
comm - compared two files line by line
cp - copy one or more files to another location
df - display free disk space
diff - display the diffrence between two file
dir - briefiy list directory contents
du - estimate file space
expand - convert tabs into space
kill - stop a process from running
logout - exit a login shell
more, less - display output on screen at a time
paste - merge lines of files
ping - test network connection
pr - prepare files for printing
return - exit shell function
rm - remove files
sleep - delay for specfied time
tail - output of last part of file
users - list users currrently logged in
usermod - modify user account
units - convert unit from one scale to another
free -m or  $free -t -m - to find the memory space in the system using command line

ssh -p 756 aaa@....

scp -P 756  filename  ab@..... :filename

Database de-limiter exchange or replace character
To convert a comma delimited database file with a  file which is tab delimited: 
$tr ',' '\t' < file > newfile

To see every process on the Unix like system use the following standard syntax:

ps -e
ps -ef
ps -eF
ps -ely
ps axu