print "The value of third element of hash4 is $hash4{three}\n"; print "The value of third element of hash5 is $hash5{six}\n"; 则运行结果为: The value of third element of hash3 is 9 The value of third element of hash4 is 3 The value of third element of hash5 is 6 原因是...
主要有keys()、values()、exists()和delete()。 keys()返回hash结构中所有key组成的列表。例如keys %hash values()则返回hash结构中所有value组成的列表。例如values %hash exists()用来检测hash结构中元素是否存在。例如exists $hash{KEY} delete()用来删除hash中的一个元素。例如delete $hash{KEY} 下面是keys和...
Perl Hash exists If an entry exist #!/usr/bin/perl -w use strict; my @names = qw( A E I B F J C G K D H L ); my %count; foreach (@names) { if (exists $count{$_}) { $count{$_}++; } else { $count{$_} = 1; } } foreach (keys %count) { print "$_ \t...
使用exists 函数检查键是否存在于哈希中。 if (exists $prices{"apple"}) { print "Apple price: $prices{'apple'}\n"; } else { print "Apple not found in prices hash.\n"; } 5.5. 获取所有键和值 keys 函数返回哈希的所有键。 values 函数返回哈希的所有值。 my @all_keys = keys %prices; ...
Processing command line arguments - @ARGV in Perl $1 $1 Always check if the regex was successful Perl 5 Regex Cheat sheet Regex capturing variables $1, $2, $3, $4, $5, $6, ... $2 $2 Perl 5 Regex Cheat sheet Regex capturing variables $1, $2, $3, $4, $5, $...
print(exists($hash{value}) ? 'There' : 'Missing',"\n"); It's not quite so clear here what we are trying to achieve, but the effect is the same as using an if or unless statement. The conditional operator is best used when you want to quickly return one of two values within ...
If not supplied, most methods do nothing to the current value--except for autoflush(), which will assume a 1 for you, just to be different. Because loading in the IO::Handle class is an expensive operation, you should learn how to use the regular built-in variables. A few of these ...
Check key existance after using 'delete' operator : delete « Hash « PerlPerl Hash delete Check key existance after using 'delete' operator $hash{fruit} = apple; $hash{sandwich} = hamburger; $hash{drink} = bubbly; delete($hash{'fruit'}); if (exists($hash{"fruit"})) { print ...
Checking if a key exists Given a multi-dimensional hash like%gradesone can check the existance of a key using theexistskeyword: if (exists $grades{"Foo Bar"}) { if (exists $grades{"Foo Bar"}{Programming}) { ... } } One should also be careful using the second-level construct without...
# Check thread's state if($thr5->is_running()) { sleep(1); } if($thr5->is_joinable()) { $thr5->join(); } # Send a signal to a thread $thr5->kill('SIGUSR1'); # Exit a thread threads->exit(); <<===Thread===>> $thread = Thread->new(\&start_sub) $thread = Th...