如何在Perl中打开一个文件的数组？ [英] How do I open an array of files in Perl?

问题描述

在Perl中，我从一个目录中读取文件，并且我想同时打开它们（但是一行一行地打开），这样我就可以执行一个使用所有第n行（如串联）的函数。

  my $ text =`ls | grep.txt; 
我的@temps = split（/ \ n /，$ text）; 
 my @files; 
为我的$我（0 .. $＃临时工）{
我的$文件; 
 open（$ file，<，$ temps [$ i]）; 
 push（@ files，$ file）; 
} 
 my $ concat; 
 for my $ i（0 .. $＃files）{
 my @blah =< $ files [$ i]>; 
 $ concat。= $ blah; 
} 
 print $ concat; 
  

我只是一堆错误，使用未初始化的值和GLOB（..）错误。那么我怎样才能做到这一点呢？ 解决方案

很多问题。首先调用ls | grep：）

让我们从一些代码开始：

首先，获取文件列表：

  my @files = glob（'* .txt'）; 
  

但是，最好测试给定的名字是否与文件或目录相关：

  my @files = grep {-f} glob（'* .txt'）; 
  

现在，我们打开这些文件来阅读它们：

  my @fhs = map {open my $ fh，'<'，$ _; $ fh} @files; 
  

但是，我们需要一种处理错误的方法 - 在我看来，最好的方法是添加： / p>

  use autodie; 
  

在脚本的开头（安装autodie，如果还没有的话）。您也可以：

 使用致命的qw（打开）; 
  

现在，我们已经得到了第一行（如您在示例中所示）所有的输入，并连接它：

  my $ concatenated =''; 
 
 for my $ fh（@fhs）{
 my $ line =< $ fh>; 
 $串联。= $ line; 
 
 
 
 
 
 $ b 
这是完美的，可读的，但仍然可以缩短，同时保持（在我看来）的可读性为：
 
 pre $  my $ concatenated = join''，map {scalar< $ _> } @fhs; 
  

效果是一样的 - $ concatenated包含所有文件的第一行

所以，整个程序看起来像这样：

$ p $ ＃！/ usr / bin / perl
使用严格;
使用警告;
使用autodie;
＃使用致命的qw（打开）; ＃取消注释，如果你没有autodie

my @files = grep {-f} glob（'* .txt'）;
my @fhs = map {open my $ fh，'<'，$ _; $ fh} @files;
my $ concatenated = join''，map {scalar <$ _> } @fhs;


现在，您可能希望连接第一行，而不是所有行。在这种情况下，你需要像下面这样的代码： $ concatenated = ... 代码

  my $ concatenated =''; 
 
 while（my $ fh = shift @fhs）{
 my $ line =< $ fh>; 
 if（defined $ line）{
 push @fhs，$ fh; 
 $串联。= $ line; 
} else {
 close $ fh; 
} 
} 
  

In perl, I read in files from a directory, and I want to open them all simultaneously (but line by line) so that I can perform a function that uses all of their nth lines together (e.g. concatenation).

my $text = `ls | grep ".txt"`;
my @temps = split(/\n/,$text);
my @files;
for my $i (0..$#temps) {
  my $file;
  open($file,"<",$temps[$i]);
  push(@files,$file);
}
my $concat;
for my $i (0..$#files) {
  my @blah = <$files[$i]>;
  $concat.=$blah;
}
print $concat;

I just a bunch of errors, use of uninitialized value, and GLOB(..) errors. So how can I make this work?

解决方案

A lot of issues. Starting with call to "ls | grep" :)

Let's start with some code:

First, let's get list of files:

my @files = glob( '*.txt' );

But it would be better to test if the given name relates to file or directory:

my @files = grep { -f } glob( '*.txt' );

Now, let's open these files to read them:

my @fhs = map { open my $fh, '<', $_; $fh } @files;

But, we need a way to handle errors - in my opinion the best way is to add:

use autodie;

At the beginning of script (and installation of autodie, if you don't have it yet). Alternatively you can:

use Fatal qw( open );

Now, that we have it, let's get the first line (as you showed in your example) from all of the inputs, and concatenate it:

my $concatenated = '';

for my $fh ( @fhs ) {
    my $line = <$fh>;
    $concatenated .= $line;
}

Which is perfectly fine, and readable, but still can be shortened, while maintaining (in my opinion) readability, to:

my $concatenated = join '', map { scalar <$_> } @fhs;

Effect is the same - $concatenated contains first lines from all files.

So, whole program would look like this:

#!/usr/bin/perl
use strict;
use warnings;
use autodie;
# use Fatal qw( open ); # uncomment if you don't have autodie

my @files        = grep { -f } glob( '*.txt' );
my @fhs          = map { open my $fh, '<', $_; $fh } @files;
my $concatenated = join '', map { scalar <$_> } @fhs;

Now, it might be that you want to concatenate not just first lines, but all of them. In this situation, instead of $concatenated = ... code, you'd need something like this:

my $concatenated = '';

while (my $fh = shift @fhs) {
    my $line = <$fh>;
    if ( defined $line ) {
        push @fhs, $fh;
        $concatenated .= $line;
    } else {
        close $fh;
    }
}

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