初识 perl

第一次用perl，简单了解下语法，好难记，不过既然perl能那么牛逼的存在这么久，必然有其过人之处，如lcov就是用perl做得。因此还是有必要学习下，至少能达到看懂别人脚本的目的，装个window版尝个新鲜。

下载：http://strawberryperl.com/

尝鲜脚本：http://learn.perl.org/examples/read_write_file.html

遇到的问题：

1. use Path::Class; 失败，提示 "Error installing package 'Path-Class': Could not locate a PPD file for package Path-Class"

解决：尝试1）C:\strawberry\perl\bin>cpan Path::Class

          尝试2）C:\strawberry\perl\bin>ppm.bat

                         PPM> install Path::Class

write.pl

#!/usr/bin/perl
use strict;
use warnings;

use Path::Class;
use autodie; # die if problem reading or writing a file

my $dir = dir("."); # /tmp

my $file = $dir->file("file.txt"); # /tmp/file.txt

# Get a file_handle (IO::File object) you can write to
my $file_handle = $file->openw();

my @list = ('a', 'list', 'of', 'lines');

foreach my $line ( @list ) {
    # Add the line to the file
    $file_handle->print($line . "\n");
}

read.pl

#!/usr/bin/perl
use strict;
use warnings;

use Path::Class;
use autodie; # die if problem reading or writing a file

my $dir = dir("."); # /tmp

my $file = $dir->file("file.txt");

# Read in the entire contents of a file
my $content = $file->slurp();
print $content;

# openr() returns an IO::File object to read from
my $file_handle = $file->openr();

# Read in line at a time
while( my $line = $file_handle->getline() ) {
        print $line;
}

补充些基本用法：

（用惯了c和python，perl的语法感觉很难用，补充些基本的语法操作先，做个记录）

#!/usr/bin/perl
use strict;
use warnings;

print "数字相关运算及处理";
print 3.14 * 3.13;

print "基本输入操作";
print "请输入\n";
my $val=<STDIN>;
$val = chomp $val;
print "您输入了【$val】";

print "列表和数组操作\n";
my @fred = qw{a b c};
print join ',', @fred;
print "\n";

my @afred = qw# a b c #;
print join ',', @afred;
print "\n";

my @bfred = qw( a b c );
print @bfred;
print "\n";

my @cfred = qw/ a b c /;
print @cfred;
print "\n";

my @array = 5..9;
print pop(@array);
print @array;
print "\n";

push @array, 1..3;
print @array;
print "\n";

@array = 1..3;
shift @array;
print @array;
print "\n";

unshift (@array, 0);
print @array;
print "\n";

@array = 1..10;
my @r_array = reverse @array;
print @r_array;

foreach (1..6)
{
    my $square = $_*$_;
    print "$_ squared is $square.\n";
}

my @items = qw( wilma dino pebbles );
my $format = "The items are :\n". ("%10s\n" x @items);
printf $format, @items;

printf "The items are:\n", ("%10s\n" x @items), @items;


my %some_hash = ("foo",35, "bar", 12.4, 2.5, "hello", "wilma", 1.72e30, "betty", "bye\n"); 
print %some_hash;
print "\n";

my %last_name = (
  "fred" => "flintstone", 
  "dino" => "di", 
  "barney" => "rubble", 
  "betty" => "rubble" ); 
print %last_name;
print "\n";
  
my %hash = ("a" => 1, "b" => 2, "c" => 3); 
my @k = keys %hash; 
my @v = values %hash;

print %hash;
print "\n";
print "打印hash的key\n";
print @k;
print "\n";
print "打印hash的values\n";
print @v;

$hash{"extra_key"} = "extra_val";
print "\n打印hash表元素\n";
while ((my $key, my $value) = each %hash) { 
   print "$key => $value\n"; 
}