Test of open and die with $!. : Special Variables « Language Basics « Perl






  1. Perl
  2. Language Basics
  3. Special Variables

Test of open and die with $!.

   


#!/usr/bin/perl -w


$filename = "nofile";

open(TMP, $filename)
    or die "Can't open \"$filename\" due to $! ";








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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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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 $_.
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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
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25.A more expanded version for showing how to use the $_
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27.Call-by-Reference and the @_ Array
28.Capturing fatal errors
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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
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57.Integer signal
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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
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82.System variables that control how write sends output to a file
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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94.Use while loop to display all entries in ENV
95.Using $, to set the separator for print command
96.Using $_ (dollar underscore)
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104.Using the $;(dollar and semicolon) variable.
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109.Using the special Perl variable $! in the message passed to die.
110.Using tr to convert all file names passed in to uppercase
111.Verify the total number of the command line parameter
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114.You display the name of the current Perl package with __PACKAGE__.
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127.undef $/;