Introduction
This chapter demonstrates about the Perl Special Variables these re-contain some predefined meaning and denoted with their real name or punctuation symbols and following are the concepts covered in this chapter.
- Special Variables
Description
Special variables in Perl are those which have some predefined which means. These variables denoted with either real Name or Punctuation symbols. we have the special variable for all the Perl supported Variables which are shown below
Array special variables
The table below demonstrates the Array special variables are shown below.
hash special variables
The table below demonstrates the hash special variables as shown below.
- scalar special variables
- Array special variables
- hash special variables
| Variable | Description |
|---|---|
| $_$ARG | newline. |
| \t | Which is the default variable used to store the current values. |
| $/ | Which is the input record seperator and have the default value of '\n' which is new line charecter. |
| $0 or $PROGRAM_NAME | Which stores the file name of the perl script. |
| $. | Which holds the current reading line number. |
| $\ | Which is the output record seperator and default values of these variable should be emepty and user can assign value to these variable. Which will be used by the print() statement while printing the output. |
| $, | Which is the output field seperator and default values of these variable should be zero and user can change the value to these variable. Which will be used by the print() statement while printing the output. |
| $# | Which is the variable used for the output format while pinting the numbers. |
| $=$FORMAT_LINES_PER_PAGE | Which hold the current page length of the read file. |
| $%$FORMAT_PAGE_NUMBER | Which hold the current page number of the read file. |
| $~$FORMAT_NAME | Format Name: Which hold the current selected output by default the file handle name format. |
| $-$FORMAT_LINES_LEFT | Which holds the number of lines left to print from the page. |
| $^$FORMAT_TOP_NAME | Which is used to hold the heading format of the file handler by default which will be TOP followed by file handle name. |
| $|$OUTPUT_AUTOFLUSH | Which is used to flush the output buffer after every write() or print() nd the default value is zero. |
| $? | Status code : Pipe and system call. which Return status of the executed command. |
| $$ | Will hold the running process number of Perl interpreter. |
| Variable | Description |
|---|---|
| @INC | Holds a list of methods, wherever Perl library modules or scripts are often looked into whereas executing the present script. This @INC is used by use and require statements to appear into those methods for library modules. |
| @ARGV | Which stores the passed command line arguments |
| @_ | Which are used in subroutines when ever passing the parameters to subroutine. |
| @F | Which is the array into which input lines are stored when auto split -a. |
| Variable | Description |
|---|---|
| %INC | File name will be the keys which will pass the values to those values by using do, use and require. |
| %ENV | System enveronment variables. |
| %SIG | Signals handler. |
Examples
The example below demonstrates the Special Variables are shown.
[perl]
my $str= "Hello World";
$str =~ /llo/;
print "$&\n"; # this will hold string of the last successful pattern match
print "$'\n"; #this will hold remaining string after patter match is done.
print "$`\n"; #this will hold the string before the patter match.
$\= "--"; #output record separator (Check output of print on output screen)
my $a =5;
my $b =6;
print "$a";
print "$b";
$\="\n";
my @array = qw(a b c d);
print "";
$"="-";# output record separator arrays (Check output of print on output screen)
print "@array";
[/perl]
Result
By running the above code in a Perl command line user can get the following output as shown in below image.
Key Points
- Special variable have some predefined mening.
- Special Variable denoted by Punctutaion symbols.
- Perl supports several special variables.