Wednesday, 18 February 2015

PERL TUTORIAL PART 2

PERL TUTORIAL PART 2 – ELECDUDE

            We hope you've gained the basic PERL knowledge from our Tutorial Part 1. In this part, let's go through about the PERL's basic input output, operators and its examples.

Click here to goto Tutorial Part 1.

BASIC I/O:

Input from STDIN
  Reading from standard input is easy, via the Perl file handle called STDIN. It returns the entire line content into a scalar variable.
$a = <STDIN>;  #the contents of input STDIN line is stored in $a
  To store many lines in the variable, the array variable is used.
@arr = <STDIN>; #the contents of each input STDIN line is stored in each element of @arr
  Note that STDIN always returns along with the NEW LINE character ie \n. To remove the new line, chomp() function is used.
$a = <STDIN>;  #the contents of input STDIN line with \n
Chomp($a); #the new line is removed.

Output to STDOUT
  Sending values to Standard Output is also easy, via the Perl file handle called STDOUT. The keyword used for this is PRINT/PRINTF
print "Hello!!";
print ("Hello!!");
print "Hell","o!!";
printf("%s","Hello!!"); #just like C language.
  All the above statement displays the same result. Arithmetic operations are also performed in the print statements.
$a=4;
print $a+$a; #prints 8
print ($a," Hello!!"); #prints 4 Hello!!
printf("%s-%d","Hello!!",$a*3); #just like C language. prints Hello!!-12

  Often printf statement is used for printing formatted text.


OPERATORS:

Perl language supports many operator types but following is a list of important and most frequently used operators:
·       Arithmetic Operators
·       Equality Operators
·       Logical Operators
·       Assignment Operators
·       Bitwise Operators
·       Logical Operators
·       Quote-like Operators
·       Miscellaneous Operators

Arithmetic Operators
Operator
Description
+
Addition - Adds values on either side of the operator
-
Subtraction - Subtracts right hand operand from left hand operand
*
Multiplication - Multiplies values on either side of the operator
/
Division - Divides left hand operand by right hand operand
%
Modulus - Divides left hand operand by right hand operand and returns remainder
**
Exponent - Performs exponential (power) calculation on operators
Equality/relational Operators
Operator
Description
==
Checks if the value of two operands are equal or not, if yes then condition becomes true.
!=
Checks if the value of two operands are equal or not, if values are not equal then condition becomes true.
<=>
Checks if the value of two operands are equal or not, and returns -1, 0, or 1 depending on whether the left argument is numerically less than, equal to, or greater than the right argument.
> 
Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true.
< 
Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true.
>=
Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true.
<=
Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true.
Equality Operators for Strings
Operator
Description
lt
Returns true if the left argument is stringwise less than the right argument.
gt
Returns true if the left argument is stringwise greater than the right argument.
le
Returns true if the left argument is stringwise less than or equal to the right argument.
ge
Returns true if the left argument is stringwise greater than or equal to the right argument.
eq
Returns true if the left argument is stringwise equal to the right argument.
ne
Returns true if the left argument is stringwise not equal to the right argument.
cmp
Returns -1, 0, or 1 depending on whether the left argument is stringwise less than, equal to, or greater than the right argument.
Assignment Operators
Operator
Description
=
Simple assignment operator, Assigns values from right side operands to left side operand
+=
Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand
-=
Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand
*=
Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand
/=
Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand
%=
Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand
**=
Exponent AND assignment operator, Performs exponential (power) calculation on operators and assign value to the left operand
Bitwise Operators
Operator
Description
&
Binary AND Operator copies a bit to the result if it exists in both operands.
|
Binary OR Operator copies a bit if it exists in eather operand.
^
Binary XOR Operator copies the bit if it is set in one operand but not both.
~
Binary Ones Complement Operator is unary and has the efect of 'flipping' bits.
<< 
Binary Left Shift Operator. The left operands value is moved left by the number of bits specified by the right operand.
>> 
Binary Right Shift Operator. The left operands value is moved right by the number of bits specified by the right operand.


Logical Operators
Operator
Description
and
Called Logical AND operator. If both the operands are true then then condition becomes true.
&&
C-style Logical AND operator copies a bit to the result if it exists in both operands.
or
Called Logical OR Operator. If any of the two operands are non zero then then condition becomes true.
||
C-style Logical OR operator copies a bit if it exists in eather operand.
not
Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.
Miscellaneous Operators
Operator
Description
.
Binary operator dot (.) concatenates two strings.
x
The repetition operator x returns a string consisting of the left operand repeated the number of times specified by the right operand.
..
The range operator .. returns a list of values counting (up by ones) from the left value to the right value
++
Auto Increment operator increases integer value by one
--
Auto Decrement operator decreases integer value by one
->
The arrow operator is mostly used in dereferencing a method or variable from an object or a class name


Quote-like Operators
Operator
Description
q{ }
Encloses a string with-in single quotes
qw{ }
Encloses a string with-in double quotes
qq{ }

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