如何判断字符串是否为空? --perl

[cuiht]

如何判断字符串是否为空?

[qbqzhanying]

#!/usr/bin/perl -w
use strict;

my $abc='aaaaa';
print "is defined:\n";
is_undef($abc);
print "is undefined:\n";
undef $abc;
is_undef($abc);
print "is '':\n";
$abc='';
is_undef($abc);

sub is_undef{
my $abc=shift;
print "1:";
if($abc){
print "is defined\n";
}else{
print "is undefined\n";
}

print "2:";
if(defined $abc){
print "is defined\n";
}else{
print "is undefined\n";
}
print "3:";
if($abc eq ''){
print "is undefined\n";
}else{
print "is defined\n";
}
print "\n";
}
------------------------------------------------
战鹰的Perl空间：http://www.blogunion.com/members/zhanying/

[w3guy]

判断字符串是否为空一般用以下可以了：
if(!$str) {
print "this is an empty/undefined string\n"
}
如果你还想区别空串"" 和未赋有效值的串可以用
if(!$str) {
if(defined $str) {
print "this is an empty string\n"

}
else {
print "this is an undefined string\n"
}
}

[okdns]

if ($xxx eq "") {}