Linux misc command handbook.

[Process]
     # List process of given executable
          $ pgrep

[User account, group, permission]
     # How do I find out what groups I belong to?
           $ groups []
           or
           $ id -Gn []
     # How to add a user to multiple groups?
           $ usermod -a -G ftp,sudo,example geek

[Date & Time]

     # Set date
          date 010100002000.00     

     #MMDDhhmmYYYY.ss Linux command to get time in milliseconds
          bash - Linux command to get time in milliseconds - Stack Overflow

          date +"%T.%N" returns the current time with nanoseconds.

               06:46:41.431857000

          date +"%T.%6N" returns the current time with nanoseconds rounded to the first 6 digits, which is microseconds.

               06:47:07.183172 

          date +"%T.%3N" returns the current time with nanoseconds rounded to the first 3 digits, which is milliseconds.

               06:47:42.773