ls

list file & directory

ls -a : Shows every files and directories including hidden ones
ls -l : Shows verbose informations (Date, Permissions etc)

tar

• Compresses multiple files or directories

• In tar, you can use 3 different compression method : tar, tar.gz, bzip2

• Compress into tar.gz file

    tar -cfvz [Filename].tar.gz [location]/
  

• Decompress the tar.gz file into local directory

    tar -xfvz [tar.gz_filename].tar.gz
  

• Decompress the tar.gz file into specific directory

    tar -xfvz [tar.gz_filename] -C [directory_location]
  

head

• head command shows the first 10 line of the file
• Can be used with cat command

 # Shows first 10 lines of the file
head [filename]

# Specifies line number you want to see
head -n*[line number]* [filename] 

# Use head command with cat command
cat [filename] | head -n******[line numbers]******

tail

• just like head command, tail shows 10 lines of the file but in opposite way
• It shows the last 10 lines of the file
• Can be used for tracking log files with -f option

# Show last 10 lines of the file
tail [filename]

# Keep tracking the file which one is keep written 
tail -f [filename]

date

• Gets current datetime
• You can choose specific format to show date
• You can get previous, post date with -d (—date) option

# Get today's date in YYYY-MM-DD format
date "+%Y-%m-%d"

# Get the yesterday's date in YYYY-MM-DD format
date -d '1 day ago' "+%Y-%m-%d"
# or else
date -d 'yesterday' "+%Y-%m-%d"
 
# Get the date of 2 months ago in YYYY-MM-DD format
date -d '2 months ago' "+%Y-%m-%d"

# Get the date of last Sunday in YYYY-MM-DD format
date -d 'last sunday' "+%Y-%m-%d"

# Get the tomorrow's date in YYYY-MM-DD format
date -d 'tomorrow' "+%Y-%m-%d"

# Get the date after 3 years later in YYYY-MM-DD format
date -d '3 years' "+%Y-%m-%d"