Perl–用调试器列出您的程序

原文:https://www . geesforgeks . org/perl-listing-你的程序带调试器/

完美的程序很难在第一次尝试中得到。他们必须经历各种调试步骤来修复所有错误。有两种类型的错误——语法错误和逻辑错误。语法错误很容易修复，而且很快就能找到。另一方面，逻辑错误很难发现和修复。因此，需要调试器来修复这些错误。

在 Perl 中，调试器是一个逐行执行程序的环境。这个过程也称为单步执行通过程序。要进入调试器，请遵循下面给出的语法:

语法:

perl -d <program_name>

要调试的示例程序:

#!/usr/bin/perl -w

# Perl program for a simple calculator
use strict;

my $op;
my $num1;
my $num2;
my $result;
my $flag;

calculator();

sub calculator 
{
    print "Enter operation you want to perform -Add, Sub, Mult, Div - ";
    chomp($op = <>);
    print "Enter first number: ";chomp($num1 = <>);
    print "Enter second number: ";chomp($num2 = <>);

    # Check for arithmetic operation
    if ($op =~ /^a/) {
        $result = $num1 + $num2;
    } elsif ($op =~ /^s/) {
        $result = $num1 - $num2;
    } elsif ($op =~ /^m/) {
        $result = $num1 * $num2;
    } elsif ($op =~ /^d/) {
        $result = $num1 / $num2;
    }

    # Print the answer of above operation
    print "Result: $result\n";

    # Calling the function recursively
    print "Do another calculation ? ";chomp($flag = <>);
    if ($flag =~ /^y/) {
        calculator();
    } else {
        print "Thank You !!\n";
    }
}

使用调试器列出示例代码

1. ‘l’ command : The ‘l’ command lets us print a partial part of our scripts. There are several versions of this command that we can use –

   • 使用“l”——从光标位置开始显示 10 行脚本。
   • 使用 l4+6–从第 4 行开始显示 6 行脚本。
   • 使用 l4-7–显示脚本的第 4 行到第 7 行。
   • 使用 l20–在第 20 行显示脚本。
   • 使用 foo–显示 foo()函数的前 10 行。

   

2. ‘-‘ command : Outputs 10 lines of script before the current line. Suppose that you are current on line 20, then, lines 9 to 19 will be displayed.

   

3. ‘w’ command : Adds a watch expression. Syntax:

   perl w $variable_name

   

4. ‘//’ and ‘??’ : // and ?? search for a given pattern in the script. The /pattern/ searches for a pattern in forward direction while, the ?pattern? searches for a pattern in the backward direction from the current position of cursor. Syntax:

   perl /pattern/ or ?pattern?

   

5. ‘S’ command : This command lists all the subroutines not matching a given pattern. Syntax:

   perl S expression

   

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