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Tuesday, 5 February 2019

UNIX COMMANDS - BC worked on UBUNTU Operating System PAGE 2 (CONT.).

bc: it is used to operate all the operators
Description: The bc command evaluates all the operators in c .
  1. Arithmetic operators
  2. Increment and decrement operators
  3. Assignment operators
  4. Relational Operators
  5. Logical operators
  6. Conditional statements
  7. Iterative statements
1.Arithmetic operator Examples:
1. Finding Sum of Two expressions
> echo "2+5" | bc
7
2. Difference of Two numbers
> echo "10-4" | bc
6
3. Multiplying two numbers
> echo "3*8" | bc
24
4. Dividing two numbers
> echo "2/3" | bc
0
> echo "5/4" | bc
1
Use the scale function to specify the number of decimal digits that the bc command should return.
> echo "scale=2;2/3" | bc
.66
5. Finding the remainder using modulus operator
> echo "6%4" | bc
2
6. Using exponent operator
> echo "10^2" | bc
100
Here the expression is evaluated as 10 to the power of 2.


2.Increment Operator Examples:
There are two kinds of increment operators. They are pre increment and post increment operators.
++var : Pre increment operator. The variable is incremented first and then the result of the variable is used.
var++ : Post increment operator. The result of the variable is used first and then the variable is incremented.
> echo "var=5;++var" | bc
6
> echo "var=5;var++" | bc
5
Here, in the second example the value of var is printed first and then it is incremented. See the below example, to see the complete incremental effect.
> echo "var=5;var++;var" | bc
5
6

Decrement Operator Examples:
Similar to the increment operators, there are two types of decrement operators.
--var : Pre decrement operator. The variable is decremented first and then the result of the variable is used.
var-- : Post decrement operator. The result of the variable is used first and then the variable is decremented.
> echo "var=5;--var"| bc
4
> echo "var=5;var--"| bc
5


3.Assignment Operator Examples:
Assigns 10 to the variable and prints the value on the terminal.
> echo "var=10;var" | bc
Increment the value of the variable by 5
> echo "var=10; var+=5;var | bc
15
The lists of assignment operators supported are:
var = value : Assign the value to the variable
var += value : similar to var = var + value
var -= value : similar to var = var - value
var *= value : similar to var = var * value
var /= value : similar to var = var / value
var ^= value : similar to var = var ^ value
var %= value : similar to var = var % value

4.Relational Operators Examples:
Relational operators are used to compare two numbers. If the comparison is true, then it returns 1. Otherwise (false), it returns 0.
expr1 < expr2 : Result is 1 if expr1 is strictly less than expr2.
expr1 <= expr2 : Result is 1 if expr1 is less than or equal to expr2.
expr1 > expr2 : Result is 1 if expr1 is strictly greater than expr2.
expr1 >= expr2 : Result is 1 if expr1 is greater than or equal to expr2.
expr1 == expr2 : Result is 1 if expr1 is equal to expr2.
expr1 != expr2 : Result is 1 if expr1 is not equal to expr2.
Examples:
> echo "10 > 5" | bc
1
> echo "1 == 2" | bc
0

5.Logical Operator Examples:
Logical operators are also mostly used in conditional statements. The result of the logical operators is either 1 (True) or 0 (false) ! expr : Result is 1 if expr is 0.
expr && expr : Result is 1 if both expressions are non-zero.
expr || expr : Result is 1 if either expression is non-zero.
> echo "4 && 10" | bc
1
> echo "0 || 0" | bc
0



6.Conditional Statement
Examples:
The syntax of if statement is
if(condition)
{
Statements
}
else
{
Statements
}
The following example shows show to use the if condition
> echo 'if(1 == 2) print "true" else print "false"' | bc
false


7.Iterative Statements:
Bc command supports the for and while loop for doing iterations. The syntax of for and while loop are shown below:
for (assignment; condition; increment)
{
statements
}
while (condition)
{
statements
}
The following examples prints numbers from 1 to 10 using the for and while loops
> echo "for(i=1;i<=10;i++) {i;}" | bc
> echo "i=1; while(i<=10) { i; i+=1}" | bc



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