Verify the total number of the command line parameter : Special Variables « Language Basics « Perl






  1. Perl
  2. Language Basics
  3. Special Variables

Verify the total number of the command line parameter

   



#!/usr/bin/perl -w
# argv2.pl

use strict;

print "program arguments:\n";

my $i = 0;

while ($i <= $#ARGV) {
    print "argument $i: $ARGV[$i]\n";
    $i++;
}








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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.
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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
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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
28.Capturing fatal errors
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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.
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55.Get local time from $^T
56.If $_contains needle, the string is printed.
57.Integer signal
58.Lines Remaining on the Page: $-
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60.Local builtin var
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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 and set environment variables?
75.Read lines from supplied filenames
76.Reference element in @_
77.Resetting array base
78.Retrieving the Entire Pattern: $&
79.Saving in the $& special scalar
80.Set the $/ and chomp
81.Special Variables
82.System variables that control how write sends output to a file
83.Test of open and die with $!.
84.The $_ Scalar Variable
85.The @* field
86.The @ISA Array and Calling Methods
87.The Argument Vector @ARGV
88.The Pattern-Matching Operator and $_
89.The Substitution Operator and $_
90.The code executes a line of code you type as long as that line doesn't start with a #
91.The environment associative array: Associative arrays %ENV holds your system's environment variables.
92.The following functions and operators work with the $_ variable by default:
93.The shift operator returns an undefined value if the array has no more elements.
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95.Use while loop to display all entries in ENV
96.Using $, to set the separator for print command
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98.Using $_ as the array index
99.Using $_ variable with while statement
100.Using %SIG to define our own signal handlers
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104.Using the $. variable.
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106.Using the @_ to reference the parameter
107.Using the Default Variable $_
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110.Using the special Perl variable $! in the message passed to die.
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112.Working with $_ usually makes programming much easier, but more confusing to the uninitiated
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114.You display the name of the current Perl package with __PACKAGE__.
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119.or die $^E;
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121.print $INC{'English.pm'};
122.print $]; (Perl version number)
123.print out all pm library location
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125.shift: defaults to shifting @ARGV
126.time - $^T
127.undef $/;