Calculations on Linux

Command Line calculator

how to perform standard calculations on the command line including addition, subtraction, multiplication, division, powers, square root, conversion.


From man pages

bc - An arbitrary precision calculator language

Addition, subtraction, multiplication and division

 $ echo '1+2' | bc    
  3    
 $ echo '5-3' | bc    
  2  
 $ echo '3*4' | bc    
  12    
 $ echo '9/2' | bc    
  4    

setting decimal places 

 $ echo 'scale=4;9/2' | bc   
  4.5000   

Square root

 $ echo 'scale=4;sqrt(25)' | bc   
  5.0000   

Conversion

converting decimal to hex

 $ echo 'obase=16;128' | bc   
  80   

 $ echo 'obase=16;255' | bc   
  FF   

converting decimal to binary

$ echo 'obase=2;255' | bc   
  11111111   

converting binary to decimal

 $ echo 'ibase=2;obase=A;0110' | bc   
  6   

converting hex to decimal

 $ echo 'ibase=16;obase=A;FF' | bc   
  255   

bc with shell scripts

 $ VAR=6 ; echo "$VAR^2" | bc  
 36  

Linux Date command

 $ date  
 Sat Sep 8 09:53:55 EEST 2012  
 $ date --date="1 year ago" +%Y%m%d-%H%M  
 20110908-0953  
 $ date --date="4 months ago" +%Y%m%d-%H%M  
 20120508-0954  
 $ date --date="100 days ago" +%Y%m%d-%H%M  
 20120531-0954  
 $ date --date="10 hours ago" +%Y%m%d-%H%M  
 20120907-2354  
 $ date --date="15 minutes ago" +%Y%m%d-%H%M  
 20120908-0939  
 $ date --date="1 year ago 15 minutes ago" +%Y%m%d-%H%M  
 20110908-0940