Read and set environment variables? : Special Variables « Language Basics « Perl

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Perl » Language Basics » Special Variables

Read and set environment variables?


   



    use Env qw(PATH TEMP);



    print "\$PATH = $PATH\n";

    print "\$TEMP = $TEMP\n";

    print "\$ENV{'TEMP'} = $ENV{'TEMP'}\n";



    $TEMP = "e:\\temp";



    print "\$TEMP = $TEMP\n";

    print "\$ENV{'TEMP'} = $ENV{'TEMP'}\n";

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1.	Special Literals
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3.	Splitting up $_ and creating an unnamed list
4.	The list separator is a comma
5.	The list separator is the empty string
6.	Passing Arguments at the Command Line
7.	Special Hashes: The %ENV Hash
8.	The %SIG hash sets signal handlers for signals.
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10.	A program that uses the $" (dollar and quotation) variable.
11.	A program that uses the $(dollar), variable.
12.	A program that uses the $< variable.
13.	A program that uses the $\(dollar and slash) variable.
14.	A simple program that assigns to $_ using .
15.	A simple version of the cat command using $_.
16.	ARGV and the Null Filehandle
17.	ARGV in Perl represents the command-line arguments.
18.	Aliases and Values
19.	Alternative names for Perl system variables.
20.	Assign elements in @_ to scalar
21.	Assign string array to @ARGV by using qw
22.	Assign value to @_
23.	Build the ARGV array with qw function
24.	@_ has runtime scope.
25.	A more expanded version for showing how to use the $_
26.	Built-in variables: $_
27.	Call-by-Reference and the @_ Array
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29.	Catching the sigINT signal
30.	Code the $_ specifically
31.	Compare value entered with number with underscore
32.	Error message is stored in $!
33.	Extracts information from the $] variable.
34.	$! is the error number
35.	$! stores the error message
36.	$" is the separator
37.	$# is the default format
38.	$(dollar), is the separator
39.	$MATCH = $&
40.	$SIG{__DIE__}
41.	$SIG{__WARN__} = 'IGNORE';
42.	$SIG{__WARN__} = sub {die "Warning: $_[0]"};
43.	$\ is 'END_OF_OUTPUT'
44.	$^ is the format header
45.	$^O stores the name of the operating system
46.	$^S: is inside eval
47.	$^W: Check the '-w switch'
48.	$^X: get the Perl execuatable file name
49.	$_ for print function
50.	$_ stores the user input
51.	$~ is the format
52.	%INC values
53.	File-searching program using $ARGV.
54.	Get Computer Name key in the %ENV
55.	Get local time from $^T
56.	If $_contains needle, the string is printed.
57.	Integer signal
58.	Lines Remaining on the Page: $-
59.	List all command line argument
60.	Local builtin var
61.	Locate all numbers less than 6
62.	Manipuate @_ and return @_
63.	Mannually change the $1 variable
64.	Match: $&
65.	Perl 5 Built-In Variables
66.	Perl's modules reside in the directories named in the @INC array, or subdirectories
67.	Perl's special arrays
68.	Perl's special variables
69.	Postmatch $'
70.	Prematch: $`
71.	Print all command line argument
72.	Print the default variable's ($_) value
73.	Quick Sum
74.	Read lines from supplied filenames
75.	Reference element in @_
76.	Resetting array base
77.	Retrieving the Entire Pattern: $&
78.	Saving in the $& special scalar
79.	Set the $/ and chomp
80.	Special Variables
81.	System variables that control how write sends output to a file
82.	Test of open and die with $!.
83.	The $_ Scalar Variable
84.	The @* field
85.	The @ISA Array and Calling Methods
86.	The Argument Vector @ARGV
87.	The Pattern-Matching Operator and $_
88.	The Substitution Operator and $_
89.	The code executes a line of code you type as long as that line doesn't start with a #
90.	The environment associative array: Associative arrays %ENV holds your system's environment variables.
91.	The following functions and operators work with the $_ variable by default:
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95.	Using $, to set the separator for print command
96.	Using $_ (dollar underscore)
97.	Using $_ as the array index
98.	Using $_ variable with while statement
99.	Using %SIG to define our own signal handlers
100.	Using @_ directly
101.	Using __LINE__ to output line number
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103.	Using the $. variable.
104.	Using the $;(dollar and semicolon) variable.
105.	Using the @_ to reference the parameter
106.	Using the Default Variable $_
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114.	You display the name of the current Perl package with __PACKAGE__.
115.	You display the name of the current file with the __FILE__ token
116.	foreach (@_)
117.	foreach loop and $_
118.	or die $!
119.	or die $^E;
120.	print "Hello, $ENV{USER}!\n";
121.	print $INC{'English.pm'};
122.	print $]; (Perl version number)
123.	print out all pm library location
124.	prints out each element of @ARGV separately
125.	shift: defaults to shifting @ARGV
126.	time - $^T
127.	undef $/;

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