使用一个循环perl读取多个文件 [英] read multiple files using one loop perl

问题描述

我有2个文件，每个文件有50行.

i have 2 files each having 50 lines..

FILE1 FILE2

FILE1 FILE2

现在，我需要在一个while或for循环中逐行读取两个文件行，并且应该将相应的行推送到2个输出数组.我已经尝试过这样的事情.但无法解决.友善的帮助

now, i need to read two file lines by line in a single while or for loop and i should push the corresponding line to the 2 output arrays. i have tried something like this. but its not working out. kindly help

#!/usr/bin/perl

   my @B =();
   my @C =();
   my @D =();
   my $lines = 0;
   my $i = 0;
   my $sizeL = 0;
   my $sizeR = 0;
  my $gf = 0; 
  $inputFile = $ARGV[0];
  $outputFile = $ARGV[1];
  open(IN1FILE,"<$inputFile") or die "cant open output file ";
  open(IN2FILE,"<$outputFile") or die "cant open output file";

  while((@B=<IN1FILE>)&&(@C= <IN2FILE>))
  {
  my $line1 = <IN1FILE>;
  my $line2 = <IN2FILE>;
  print $line2;
  }

这里数组2没有得到构建..但是我得到了数组1的值.

Here array 2 is not getting build.. but i am getting array 1 value.

推荐答案

在循环条件下，您将整个文件读入它们的数组.然后将列表分配用作布尔值.这仅工作一次，因为在评估条件之后将读取文件.另外，循环中的读取行将返回undef.

In your loop condition, you read the whole files into their arrays. The list assignment is then used as a boolean value. This works only once, as the files will be read after the condition has been evaluated. Also, the readlines inside the loop will return undef.

这是应该起作用的代码:

Here is code that should work:

my (@lines_1, @lines_2);
# read until one file hits EOF
while (!eof $INFILE_1 and !eof $INFILE_2) {
  my $line1 = <$INFILE_1>;
  my $line2 = <$INFILE_2>;
  say "from the 1st file: $line1";
  say "from the 2nd file: $line2";
  push @lines_1, $line1;
  push @lines_2, $line2;
}

您也可以这样做:

my (@lines_1, @lines_2);
# read while both files return strings
while (defined(my $line1 = <$INFILE_1>) and defined(my $line2 = <$INFILE_2>)) {
  say "from the 1st file: $line1";
  say "from the 2nd file: $line2";
  push @lines_1, $line1;
  push @lines_2, $line2;
}

或者:

# read once into arrays
my @lines_1 = <$INFILE_1>;
my @lines_2 = <$INFILE_2>;
my $min_size = $#lines_1 < $#lines_2 ? $#lines_1 : $#lines_2; # $#foo is last index of @foo
# then interate over data
for my $i ( 0 .. $min_size) {
  my ($line1, $line2) = ($lines_1[$i], $lines_2[$i]);
  say "from the 1st file: $line1";
  say "from the 2nd file: $line2";
}

当然，我假设您做了use strict; use warnings;和use feature 'say'，并且将open的3-arg形式与词汇文件句柄一起使用:

Of course, I am assuming that you did use strict; use warnings; and use feature 'say', and used the 3-arg form of open with lexical filehandles:

my ($file_1, $file_2) = @ARGV;
open my $INFILE_1, '<', $file_1 or die "Can't open $file_1: $!"; # also, provide the actual error!
open my $INFILE_2, '<', $file_2 or die "Can't open $file_2: $!";

我还敦促您使用描述性的变量名而不是单个字母，并在尽可能深的范围内声明变量-在开始时声明vars几乎与使用错误的，错误的全局变量相同.

I also urge you to use descriptive variable names instead of single letters, and to declare your variables in the innermost possible scope — declaring vars at the beginning is almost the same as using bad, bad globals.

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