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输出时缓冲区疑惑

时间：2010-11-14

来源：互联网

Mastering Perl 上的一个例子

#!/usr/bin/perl
use Devel::Size qw(size);
my $n;
print_message( "Before I do anything" );
print "Size is ", size( \$n );
print_message( "After I assign a string" );
$n = '1';
print "Size is ", size( \$n );
print_message( "After I use it as a number" );
my $m = $n + 1;
print "Size is ", size( \$n );
sub print_message { print "\n", "-" x 50, "\n$_[0]\n", "-" x 50, "\n" }

复制代码

输出：
--------------------------------------------------
Before I do anything
--------------------------------------------------
Size is 24
--------------------------------------------------
After I assign a string
--------------------------------------------------
Size is 56
--------------------------------------------------
After I use it as a number
--------------------------------------------------
Size is 64

因为好几个地方都用到print_message,每次复制粘贴比较麻烦，就把它作成一个小的模块

#Print.pm
package Print;
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT = qw(print_message);
our @EXPORT_OK = qw();
our $VERSION = 1.00;
sub print_message {
print STDERR "\n", "-" x 50,
"\n$_[0]\n", "-" x 50, "\n";
}
1
#size.plx
#!/usr/bin/perl
use strict;
use warnings;
use Devel::Size qw/size/;
use Print;
my $n;
print_message("Before I do anything");
print "Size is ", size(\$n);
print_message("After I do something");
$n = '1';
print "Size is ", size(\$n);
print_message("After I do anything");
my $m = $n + 1;
print "Size is ", size(\$n);

复制代码

输出变成这样了:
--------------------------------------------------
Before I do anything
--------------------------------------------------

--------------------------------------------------
After I do something
--------------------------------------------------

--------------------------------------------------
After I do anything
--------------------------------------------------
Size is 24Size is 56Size is 64

我的解决方法有两个：
1. 在size.plx 文件开始设置 local $| = 1;
2. 在