我怎样才能在Perl中同时浏览两个文件? [英] How can I walk through two files simultaneously in Perl?
问题描述
我有两个文本文件,其中包含位置
- 值的列数据
,按<$ c排序第一个文件的例子(文件 A
) >):
100 1
101 1
102 0
103 2
104 1
...
以下是第二个文件(
$ b $ $ $ $ $ $ $ $ $ ...
100 2
101 1
192 3
193 1
...
不是将两个文件中的一个读入哈希表,这个哈希表由于内存限制而过分,我想要做的是同时遍历两个文件,时尚。
这意味着我想通过 A
或 B
并比较 position
值。
如果两个位置相等,然后我执行一个计算与该位置相关的值。否则,如果职位不相等,我移动文件行 A
或文件 B
直到位置相等(当我再次执行我的计算)或者我达到了两个文件的EOF。
有没有办法在Perl中这样做?
看起来像一个可能偶然发现的问题,例如数据库表数据与键和值。这是rjp提供的伪代码的实现。
#!/ usr / bin / perl
严格使用
使用警告;
sub read_file_line {
my $ fh = shift;
if($ fh and my $ line =< $ fh>){
chomp $ line;
return [split(/ \ t /,$ line)];
}
return;
计算{
#做一些2值的操作
}
open(my $ f1,file1) ;
open(my $ f2,file2);
my $ pair1 = read_file_line($ f1);
my $ pair2 = read_file_line($ f2); $
$ b while($ pair1 and $ pair2){
if($ pair1-> [0]< $ pair2-> [0]){
$ pair1 = read_file_line($ F1);
} elsif($ pair2-> [0]< $ pair1-> [0]){
$ pair2 = read_file_line($ f2);
} else {
compute($ pair1-> [1],$ pair2-> [1]);
$ pair1 = read_file_line($ f1);
$ pair2 = read_file_line($ f2);
}
}
close($ f1);
close($ f2);
希望这有助于您!
I have two text files that contain columnar data of the variety position
-value
, sorted by position
.
Here is an example of the first file (file A
):
100 1
101 1
102 0
103 2
104 1
...
Here is an example of the second file (B
):
20 0
21 0
...
100 2
101 1
192 3
193 1
...
Instead of reading one of the two files into a hash table, which is prohibitive due to memory constraints, what I would like to do is walk through two files simultaneously, in a stepwise fashion.
What this means is that I would like to stream through lines of either A
or B
and compare position
values.
If the two positions are equal, then I perform a calculation on the values associated with that position.
Otherwise, if the positions are not equal, I move through lines of file A
or file B
until the positions are equal (when I again perform my calculation) or I reach EOF of both files.
Is there a way to do this in Perl?
Looks like a problem one would likely stumble upon, for example database table data with keys and values. Here's an implementation of the pseudocode provided by rjp.
#!/usr/bin/perl
use strict;
use warnings;
sub read_file_line {
my $fh = shift;
if ($fh and my $line = <$fh>) {
chomp $line;
return [ split(/\t/, $line) ];
}
return;
}
sub compute {
# do something with the 2 values
}
open(my $f1, "file1");
open(my $f2, "file2");
my $pair1 = read_file_line($f1);
my $pair2 = read_file_line($f2);
while ($pair1 and $pair2) {
if ($pair1->[0] < $pair2->[0]) {
$pair1 = read_file_line($f1);
} elsif ($pair2->[0] < $pair1->[0]) {
$pair2 = read_file_line($f2);
} else {
compute($pair1->[1], $pair2->[1]);
$pair1 = read_file_line($f1);
$pair2 = read_file_line($f2);
}
}
close($f1);
close($f2);
Hope this helps!
这篇关于我怎样才能在Perl中同时浏览两个文件?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!