已经解决.结贴 脚本 Perl - 关于模块 Tie::File 的几点疑问

sunzhiguolu

自己顶下...
哪位大神能够说下 Tie::File 模块的具体应用场景吗? 以及 memory 选项 具体的含义?
对于 Tie::File 模块, 我先说下我的理解:
1.> 适用于顺序处理大型的记录型文件
2.> 对于数组的修改直接反映到关联的文件
3.> 对于反复处理文件数据提供了一定的便利性

对了, 还有数组的 delete 函数使用场景...

如果哪里有遗漏, 错误还请大家给予指点及帮助...

MMMIX

sunzhiguolu 发表于 2015-12-03 19:36
以及 memory 选项 具体的含义?

能不能把 Tie::File 的文档仔细的看下？

sunzhiguolu

回复 12# MMMIX
没有特别的地方啊!
以下内容来自:
perldoc.perl.org

1.>
This is an upper limit on the amount of memory that Tie::File will consume at any time while managing the file. This is used for two things: managing the read cache and managing the deferred write buffer.

Records read in from the file are cached, to avoid having to re-read them repeatedly. If you read the same record twice, the first time it will be stored in memory, and the second time it will be fetched from the read cache. The amount of data in the read cache will not exceed the value you specified for memory . If Tie::File wants to cache a new record, but the read cache is full, it will make room by expiring the least-recently visited records from the read cache.

The default memory limit is 2Mib. You can adjust the maximum read cache size by supplying the memory option. The argument is the desired cache size, in bytes.
2.>
Setting the memory limit to 0 will inhibit caching; records will be fetched from disk every time you examine them.

The memory value is not an absolute or exact limit on the memory used. Tie::File objects contains some structures besides the read cache and the deferred write buffer, whose sizes are not charged against memory .

The cache itself consumes about 310 bytes per cached record, so if your file has many short records, you may want to decrease the cache memory limit, or else the cache overhead may exceed the size of the cached data.

   

stanley_tam

感觉上面说的还算清楚吧，你还想要啥额
Records read in from the file are cached, to avoid having to re-read them repeatedly.
The default memory limit is 2Mib. You can adjust the maximum read cache size by supplying the memory option. The argument is the desired cache size, in bytes.

sunzhiguolu

回复 14# stanley_tam
我是想问下, 为什么延迟写入没有延迟的效果.


   

MMMIX

回复 13# sunzhiguolu


    文档只看一部分这个坏毛病你是从哪学的？

sunzhiguolu

回复 16# MMMIX

文档只看一部分这个坏毛病你是从哪学的？

自学成才.
perldoc -m #查模块不会查

   

104359176

回复 2# sunzhiguolu


    我也认为对数组的 delete 没有什么意义。splice 只能提取连续的数组片段，更灵活的提取办法是：grep

sunzhiguolu

回复 18# 104359176

我也认为对数组的 delete 没有什么意义。splice 只能提取连续的数组片段，更灵活的提取办法是：grep

前辈您好, 我说的不是您那个意思.

1. 
   
2. #!/usr/bin/perl
   
3. use strict;
   
4. use warnings;
   
5. 
   
6. 
   
7. my @aAnimals = qw (tiger fox lion);
   
8. delete $aAnimals[0];          #=> scalar (@aAnimals) = 3, $aData[0] = undef;
   
9. splice (@aAnimals, 0, 1);     #=> scalar (@aAnimals) = 2
   

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我是想问 数组的 delete 函数该用在什么时候.

sunzhiguolu

Tie::File 模块的 memory 选项, 对于延迟写入的效果.
是否因为我的程序已经执行完成了, 所以才有了我马上看到文件变化的情况.
我把代码中加入一个 sleep 函数, 好像有了点效果. 不知理解的是否正确, 如有哪里不对还请大家指点帮助, 谢谢...

1. 
   
2. ...
   
3. use Tie::File;
   
4. 
   
5. my ($sFile, @aData) = ('z:\data.txt');
   
6. tie (@aData, 'Tie::File', $sFile);
   
7. $aData[0] .= "\tAppend text";
   
8. sleep 10;
   
9. untie (@aData);
   

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