perl相关文章
2016-07-14 19:49
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1 Perl使用FindBin模块解决脚本中的路径问题
2 在Perl中使用Getopt::Long模块来接收用户命令行参数
3 use POSIX qw(strftime)
4 use File::Copy qw(copy)
5 use Data::Dumper
6 DBI 数据库模块剖析
7 使用Perl的system运行外部程序
8 perl q qq qr qw qx 区别与使用方法
9 perl的变量与括号
10 Parallel::ForkManager(注意下面关于start and next的解释)
The and isn't just a "do this then this", it's a shortcut operator. If the $manager->start evaluates
to something true, it does the next, but otherwise it doesn't.
In the particular case of Parallel::ForkManager, the ->start method returns values just
like fork does; in the parent, it returns the pid of the child (which is a positive integer, and thus true), and in the child, it
returns 0 (which is false).
So, the result is that in the parent process, the next happens, and it goes around and spawns off the next one (which is what you want the parent to do). In the child, since the ->start returns a false
value, the and isn't followed, and it goes ahead and does the bits of actual work. The child does its thing (with system in
this case), and then calls the ->finish method, which is equivalent to exit, so the child doesn't go
back to the top of the loop and try spawning off more children (that's the parent's job).
11 控制:unless,until,next,redo,last
2 在Perl中使用Getopt::Long模块来接收用户命令行参数
3 use POSIX qw(strftime)
4 use File::Copy qw(copy)
5 use Data::Dumper
6 DBI 数据库模块剖析
7 使用Perl的system运行外部程序
8 perl q qq qr qw qx 区别与使用方法
9 perl的变量与括号
10 Parallel::ForkManager(注意下面关于start and next的解释)
The and isn't just a "do this then this", it's a shortcut operator. If the $manager->start evaluates
to something true, it does the next, but otherwise it doesn't.
In the particular case of Parallel::ForkManager, the ->start method returns values just
like fork does; in the parent, it returns the pid of the child (which is a positive integer, and thus true), and in the child, it
returns 0 (which is false).
So, the result is that in the parent process, the next happens, and it goes around and spawns off the next one (which is what you want the parent to do). In the child, since the ->start returns a false
value, the and isn't followed, and it goes ahead and does the bits of actual work. The child does its thing (with system in
this case), and then calls the ->finish method, which is equivalent to exit, so the child doesn't go
back to the top of the loop and try spawning off more children (that's the parent's job).
11 控制:unless,until,next,redo,last
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