跳过数组中的一行，Perl

Question

我对 Perl 比较陌生，我遇到了这个项目，我遇到了一些困难。该项目的目标是比较两个csv文件，其中一个文件将包含：$name、$model$version另一个将包含：$name 2，$disk，$storage最后，RESULT 文件将包含匹配的行，并将信息放在一起，如下所示：$name、$model、$version、$disk，$storage。

我已经设法做到了这一点，但我的问题是，当缺少程序的元素之一中断时。当它遇到文件中缺少元素的行时，它会在该行处停止。如何解决此问题？关于我如何让它跳过那条线并继续前进的任何建议或方法？

这是我的代码：

open( TESTING, '>testing.csv' ); # Names will be printed to this during testing. only .net       ending names should appear
open( MISSING, '>Missing.csv' ); # Lines with missing name feilds will appear here.
#open (FILE,'C:Usershp-laptopDesktopfile.txt');
#my (@array) =<FILE>;
my @hostname;    #stores names
#close FILE;
#***** TESTING TO SEE IF ANY OF THE LISTED ITEMS BEGIN WITH A COMMA AND DO NOT HAVE A   NAME.
#***** THESE OBJECTS ARE PLACED INTO THE MISSING ARRAY AND THEN PRINTED OUT IN A SEPERATE
#***** FILE.
#open (FILE,'C:Usershp-laptopDesktopfile.txt');
#test
if ( open( FILE, "file.txt" ) ) {
}
else {
  die " Cannot open file 1!n:$!";
}
$count = 0;
$x     = 0;
while (<FILE>) {
  ( $name, $model, $version ) = split(",");    #parsing
  #print $name;
  chomp( $name, $model, $version );
  if ( ( $name =~ /^s*$/ )
      && ( $model   =~ /^s*$/ )
      && ( $version =~ /^s*$/ ) )    #if all of the fields  are blank ( just a blank space)
  {
    #do nothing at all
  }
  elsif ( $name =~ /^s*$/ ) {   #if name is a blank
    $name =~ s/^s*/missing/g;
    print MISSING "$name,$model,$versionn";
    #$hostname[$count]=$name;
    #$count++;
  }
  elsif ( $model =~ /^s*$/ ) {   #if model is blank
    $model =~ s/^s*/missing/g;
    print MISSING"$name,$model,$versionn";
  }
  elsif ( $version =~ /^s*$/ ) {   #if version is blank
    $version =~ s/^s*/missing/g;
    print MISSING "$name,$model,$versionn";
  }
  # Searches for .net to appear in field "$name" if match, it places it into hostname array.
  if ( $name =~ /.net/ ) {
    $hostname[$count] = $name;
    $count++;
  }
#searches for a comma in the name feild, puts that into an array and prints the line into the missing file.
#probably won't have to use this, as I've found a better method to test all of the    feilds ( $name,$model,$version)
#and put those into the missing file. Hopefully it works.
#foreach $line (@array)
#{
#if($line =~ /^,+/)
#{
#$line =~s/^,*/missing,/g;
#$missing[$x]=$line;
#$x++;
#}
#}
}
close FILE;
for my $hostname (@hostname) {
  print TESTING $hostname . "n";
}
#for my $missing(@missing)
#{
# print MISSING $missing;
#}
if ( open( FILE2, "file2.txt" ) ) {    #Run this if the open succeeds
  #open outfile and print starting header
  open( RESULT, '>resultfile.csv' );
  print RESULT ("name,Model,version,Disk, storagen");
}
else {
  die " Cannot open file 2!n:$!";
}
$count = 0;
while ( $hostname[$count] ne "" ) {
  while (<FILE>) {
    ( $name, $model, $version ) = split(",");    #parsing
    #print $name,"n";
    if ( $name eq $hostname[$count] )    # I think this is the problem area.
    {
      print $name, "n", $hostname[$count], "n";
      #print RESULT"$name,$model,$version,";
      #open (FILE2,'C:Usershp-laptopDesktopfile2.txt');
      #test
      if ( open( FILE2, "file2.txt" ) ) {
      }
      else {
        die " Cannot open file 2!n:$!";
      }
      while (<FILE2>) {
        chomp;
        ( $name2, $Dcount, $vname ) = split(",");    #parsing
        if ( $name eq $name2 ) {
          chomp($version);
          print RESULT"$name,$model,$version,$Dcount,$vnamen";
        }
      }
    }
    $count++;
  }
  #open (FILE,'C:Usershp-laptopDesktopfile.txt');
  #test
  if ( open( FILE, "file.txt" ) ) {
  }
  else {
    die " Cannot open file 1!n:$!";
  }
}
close FILE;
close RESULT;
close FILE2;

Answer 1

我认为你想要下一个，它可以让您立即完成当前迭代并开始下一个迭代：

while (<FILE>) {
  ( $name, $model, $version ) = split(",");
  next unless( $name && $model && $version );
  ...;
  }

您使用的条件取决于您接受的值。在我的示例中，我假设所有值都需要为 true。如果它们不需要成为空字符串，也许您可以检查长度：

while (<FILE>) {
  ( $name, $model, $version ) = split(",");
  next unless( length($name) && length($model) && length($version) );
  ...;
  }

如果您知道如何验证每个字段，则可能有这些字段的子例程：

while (<FILE>) {
  ( $name, $model, $version ) = split(",");
  next unless( length($name) && is_valid_model($model) && length($version) );
  ...;
  }
sub is_valid_model { ... }

现在你只需要决定如何将其集成到你已经在做的事情中。

Answer 2

您应该首先将use strict和use warnings添加到程序的顶部，并在首次使用时声明所有带有my的变量。这将揭示许多简单的错误，否则很难发现。

您还应该使用 open 和词法文件句柄的三个参数，用于检查打开文件异常的 Perl 习惯用法是将or die添加到open调用中。 if带有成功路径空块的语句会浪费空间并变得不可读。open调用应如下所示

open my $fh, '>', 'myfile' or die "Unable to open file: $!";

最后，在处理CSV文件时使用Perl模块要安全得多，因为使用简单的split /,/有很多陷阱。Text::CSV模块已为您完成了所有工作，可在CPAN上使用。

您的问题是，在读取第一个文件的末尾后，在第二个嵌套循环中再次从同一句柄读取之前，您不会倒带或重新打开它。这意味着不会再从该文件读取数据，程序的行为就像是空的一样。

为了

配对相应的记录而通读同一文件数百次是一种糟糕的策略。如果文件的大小合理，则应在内存中构建数据结构来保存信息。Perl 哈希是理想的，因为它允许您立即查找与给定名称相对应的数据。

我已经编写了您的代码修订版来演示这些要点。测试代码对我来说会很尴尬，因为我没有示例数据，但如果您仍然遇到问题，请告诉我们。

use strict;
use warnings;
use Text::CSV;
my $csv = Text::CSV->new;
my %data;
# Read the name, model and version from the first file. Write any records
# that don't have the full three fields to the "MISSING" file
#
open my $f1, '<', 'file.txt' or die qq(Cannot open file 1: $!);
open my $missing, '>', 'Missing.csv' 
    or die qq(Unable to open "MISSING" file for output: $!);
    # Lines with missing name fields will appear here.
while ( my $line = csv->getline($f1) ) {
  my $name = $line->[0];
  if (grep $_, @$line < 3) {
    $csv->print($missing, $line);
  }
  else {
    $data{$name} = $line if $name =~ /.net$/i;
  }
}
close $missing;
# Put a list of .net names found into the testing file
#
open my $testing, '>', 'testing.csv'
    or die qq(Unable to open "TESTING" file for output: $!);
    # Names will be printed to this during testing. Only ".net" ending names should appear
print $testing "$_n" for sort keys %data;
close $testing;
# Read the name, disk and storage from the second file and check that the line
# contains all three fields. Remove the name field from the start and append
# to the data record with the matching name if it exists.
#
open my $f2, '<', 'file2.txt' or die qq(Cannot open file 2: $!);
while ( my $line = $csv->getline($f2) ) {
  next unless grep $_, @$line >= 3;
  my $name = shift @$line;
  next unless $name =~ /.net$/i;
  my $record = $data{$name};
  push @$record, @$line if $record;
}
# Print the completed hash. Send each record to the result output if it
# has the required five fields
#
open my $result, '>', 'resultfile.csv' or die qq(Cannot open results file: $!);
$csv->print($result, qw( name Model version Disk storage ));
for my $name (sort keys %data) {
  my $line = $data{$name};
  if (grep $_, @$line >= 5) {
    $csv->print($result, $data{$name});
  }
}