Perl的STDOUT问题

Question

I wrote a little piece of code in order to process some XML files recursively on Windows using XMLLINT

#!C:\Perl64\bin\perl
$ENV{PATH} = 'C:\Users\NLP-Lingua\Desktop\echos';
my $racine = $ENV{PATH};
&recurse($racine);

sub recurse {
    my $dossier = shift(@_);
    opendir(DOSSIER, $dossier);
    my @files = readdir (DOSSIER);
    #print "liste des fichier de $dossier : @files\n"; 
    foreach my $file (@files) {
        next if $file =~ /^\.\.?$/;
        my $file = $dossier."/".$file;
        if (-f $file) {
            #print $file, "\n";
            if (($file =~ /\.xml$/)) {
system("C://toolslibxml//xmllint.exe --dropdtd --noent $file > $file\_out");
open (OUT, ">$file\_translated.xml");
                }
                close(IN);
            }
        }
        if (-d $file) {
            &recurse($file);
        }
    }

close IN;
close OUT; 

This code works perfectly on Ubuntu but I'm having troubles redirecting the output of

C://toolslibxml//xmllint.exe --dropdtd --noent $file into a file, if I take the operartor ">" all the outputs are printed into the screen but if I put it back the file are empty, I have tried also a variation using back-quoats and a variable the result was the same

On prompt command the command C://toolslibxml//xmllint.exe --dropdtd --noent file > out_putfile work prefectly so it's very strange

Thanks in advance

Answer 1

TL;DR: Skip to the end for my guess to the solution.

I will go through your script and comment on what you are doing. There are a lot of questionable code.

#!C:\Perl64\bin\perl

The shebang is ignored in Windows, but any switches are parsed. You should be using use strict; use warnings; use strict; use warnings; -- the problems do not go away if you don't use them, they are just hidden.

$ENV{PATH} = 'C:\Users\NLP-Lingua\Desktop\echos';
my $racine = $ENV{PATH};
&recurse($racine);

As near as I can tell, there is no reason to involve $ENV{PATH} here at all. This only controls what programs the shell your Perl program is running in can access. By setting it to this folder, you are basically restricting your temporary shell from accessing programs in Windows PATH , and I doubt that is what you are trying to do.

Also, you should not use & to prefix subroutines, that is old style, and it is used to override prototypes. And if you don't know what that means, check perldoc perlsub , or just do as I recommend.

This whole code can simply be written:

recurse('C:\Users\NLP-Lingua\Desktop\echos');

sub recurse {
    my $dossier = shift(@_);
    opendir(DOSSIER, $dossier);
    my @files = readdir (DOSSIER);
    #print "liste des fichier de $dossier : @files\n"; 
    foreach my $file (@files) {
        next if $file =~ /^\.\.?$/;
        my $file = $dossier."/".$file;
        if (-f $file) {
            #print $file, "\n";
            if (($file =~ /\.xml$/)) {
system("C://toolslibxml//xmllint.exe --dropdtd --noent $file > $file\_out");

As I said in the comments, $file\\_out is a strange way to prevent $file_out to be interpolated as a variable. You should use ${file}_out , or better yet, make a new variable: my $file_out = $file . "_out"; my $file_out = $file . "_out";

open (OUT, ">$file\_translated.xml");

You never use this file handle, so you will be filling your directories with empty files. And every time you run this script, you will likely create even more empty files.

                close(IN);

You never opened this file handle.

As for why your program is not working, I am guessing it is this line:

    my $file = $dossier."/".$file;

When you interpolate this, you get something like foo/bar.xml , and / is used by Windows cmd shell. Use backslash, or better yet, use File::Spec::catfile :

use File::Spec;
my $file = File::Spec->catfile($dossier, $file);

This will create a path with suitable directory separators for the system the program is running on.