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Full Discussion: Please explain this command?
Top Forums UNIX for Dummies Questions & Answers Please explain this command? Post 302751227 by samnyc on Thursday 3rd of January 2013 12:56:16 PM
Old 01-03-2013
Please explain this command?

Hi,

I saw this. But I don't know why we need this?

Code:
 
ls mydir > foo.txt    ##   I know what this will do, it will take the results and write to the file called foo.txt
 
ls mydir > foo.txt 2>&1  ##   Don't know why we need 2>&1

Thanks.
 

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Path::Class(3pm)					User Contributed Perl Documentation					  Path::Class(3pm)

NAME
Path::Class - Cross-platform path specification manipulation VERSION
version 0.26 SYNOPSIS
use Path::Class; my $dir = dir('foo', 'bar'); # Path::Class::Dir object my $file = file('bob', 'file.txt'); # Path::Class::File object # Stringifies to 'foo/bar' on Unix, 'fooar' on Windows, etc. print "dir: $dir "; # Stringifies to 'bob/file.txt' on Unix, 'bobfile.txt' on Windows print "file: $file "; my $subdir = $dir->subdir('baz'); # foo/bar/baz my $parent = $subdir->parent; # foo/bar my $parent2 = $parent->parent; # foo my $dir2 = $file->dir; # bob # Work with foreign paths use Path::Class qw(foreign_file foreign_dir); my $file = foreign_file('Mac', ':foo:file.txt'); print $file->dir; # :foo: print $file->as_foreign('Win32'); # foofile.txt # Interact with the underlying filesystem: # $dir_handle is an IO::Dir object my $dir_handle = $dir->open or die "Can't read $dir: $!"; # $file_handle is an IO::File object my $file_handle = $file->open($mode) or die "Can't read $file: $!"; DESCRIPTION
"Path::Class" is a module for manipulation of file and directory specifications (strings describing their locations, like '/home/ken/foo.txt' or 'C:WindowsFoo.txt') in a cross-platform manner. It supports pretty much every platform Perl runs on, including Unix, Windows, Mac, VMS, Epoc, Cygwin, OS/2, and NetWare. The well-known module "File::Spec" also provides this service, but it's sort of awkward to use well, so people sometimes avoid it, or use it in a way that won't actually work properly on platforms significantly different than the ones they've tested their code on. In fact, "Path::Class" uses "File::Spec" internally, wrapping all the unsightly details so you can concentrate on your application code. Whereas "File::Spec" provides functions for some common path manipulations, "Path::Class" provides an object-oriented model of the world of path specifications and their underlying semantics. "File::Spec" doesn't create any objects, and its classes represent the different ways in which paths must be manipulated on various platforms (not a very intuitive concept). "Path::Class" creates objects representing files and directories, and provides methods that relate them to each other. For instance, the following "File::Spec" code: my $absolute = File::Spec->file_name_is_absolute( File::Spec->catfile( @dirs, $file ) ); can be written using "Path::Class" as my $absolute = Path::Class::File->new( @dirs, $file )->is_absolute; or even as my $absolute = file( @dirs, $file )->is_absolute; Similar readability improvements should happen all over the place when using "Path::Class". Using "Path::Class" can help solve real problems in your code too - for instance, how many people actually take the "volume" (like "C:" on Windows) into account when writing "File::Spec"-using code? I thought not. But if you use "Path::Class", your file and directory objects will know what volumes they refer to and do the right thing. The guts of the "Path::Class" code live in the "Path::Class::File" and "Path::Class::Dir" modules, so please see those modules' documentation for more details about how to use them. EXPORT The following functions are exported by default. file A synonym for "Path::Class::File->new". dir A synonym for "Path::Class::Dir->new". If you would like to prevent their export, you may explicitly pass an empty list to perl's "use", i.e. "use Path::Class ()". The following are exported only on demand. foreign_file A synonym for "Path::Class::File->new_foreign". foreign_dir A synonym for "Path::Class::Dir->new_foreign". Notes on Cross-Platform Compatibility Although it is much easier to write cross-platform-friendly code with this module than with "File::Spec", there are still some issues to be aware of. o On some platforms, notably VMS and some older versions of DOS (I think), all filenames must have an extension. Thus if you create a file called foo/bar and then ask for a list of files in the directory foo, you may find a file called bar. instead of the bar you were expecting. Thus it might be a good idea to use an extension in the first place. AUTHOR
Ken Williams, KWILLIAMS@cpan.org COPYRIGHT
Copyright (c) Ken Williams. All rights reserved. This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. SEE ALSO
Path::Class::Dir, Path::Class::File, File::Spec perl v5.14.2 2012-06-15 Path::Class(3pm)
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