while (($key, $value) = each %hash){ print "$key => $value\n"; } 检测元素是否存在 如果你在哈希中读取不存在的 key/value 对 ,会返回undefined值,且在执行时会有警告提醒。为了避免这种情况,我们可以使用exists函数来判断key是否存在,存在的时候读取: #!/usr/bin/perl %data = ('
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 ...
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...
1. Determine if a particular key exists 2. The exists function returns true if a hash key (or array index) has been defined, and false if not. 3. To tell if a given key name exists in a hash, you can use the exists operator. 4. Using 'if exists' to check the entry in hash...
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...
使用exists 函数检查键是否存在于哈希中。 if (exists $prices{"apple"}) { print "Apple price: $prices{'apple'}\n"; } else { print "Apple not found in prices hash.\n"; } 5.5. 获取所有键和值 keys 函数返回哈希的所有键。 values 函数返回哈希的所有值。 my @all_keys = keys %prices; ...
checkeq(1) checknr(1) chgrp(1) chgrp(1g) chkey(1) chmod(1) chmod(1g) chown(1) chown(1B) chown(1g) chroot(1g) ckdate(1) ckgid(1) ckint(1) ckitem(1) ckkeywd(1) ckpath(1) ckrange(1) ckstr(1) cksum(1) cksum(1g) cktime(1) ckuid(1) ckyorn(1) clear(1) clear(...
print "$key => $value"; } # process hash in key's order foreach $key (sort keys %hash) { $value=$hash{$key}; print "$key => $value"; } # exists: if exist some key if (exists $book{"dino"}) { ... } # delete the key and the value delete $books{$person}; # %ENV...
checkeq(1) checknr(1) chgrp(1) chgrp(1g) chkey(1) chmod(1) chmod(1g) chown(1) chown(1B) chown(1g) chroot(1g) ckdate(1) ckgid(1) ckint(1) ckitem(1) ckkeywd(1) ckpath(1) ckrange(1) ckstr(1) cksum(1) cksum(1g) cktime(1) ckuid(1) ckyorn(1) clear(1) clear(...
As you can see in the above lines of code, we are using exists function in Perl to check the element in array and hash. But for this example, we are checking for a hash. Firstly, we have created one hash object and assign several values as key-value pairs. We have kept the key ...