readdir: is there a way to reset cursor to beginning?
in [Perl]
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From: Patrick H. on 16 Feb 2010 00:26 Hi, I am toying around with the directory operations chapter of "Learning Perl" and ran into a bit of a snag. I am trying to open a directory, output all the -f files to a @files array and all the -d files to a @folders array. The problem is it seems to only work for the first instance of readdir I use; they both work individually when I comment the other out, but when I have them both only the first array is populated. Do I need to closedir and then opendir again, or is there a way for me to reset the cursor (if that is even the right terminology)? Below is my code, and advice would be appreciated. Patrick H. #!/usr/bin/perl -w use strict; # folder to scan my $folder = 'c:/'; # open folder opendir C_DRIVE, $folder or die "problem reading $folder: $!"; my @files = grep { -f "$folder/$_" } readdir(C_DRIVE); # all files my @folders = grep { -d "$folder/$_" } readdir(C_DRIVE); # all folders # close folder closedir C_DRIVE; # test results print "your files: @files\n"; print "your folders: @folders\n";
From: J�rgen Exner on 16 Feb 2010 00:42 "Patrick H." <patrickh(a)gmail.com> wrote: >I am trying to open a directory, output all the -f files to a @files >array and all the -d files to a @folders array. The problem is it >seems to only work for the first instance of readdir I use; they both >work individually when I comment the other out, but when I have them >both only the first array is populated. Do I need to closedir and then >opendir again, or is there a way for me to reset the cursor (if that >is even the right terminology)? You could try seek(). Although it is documented only for filehandles, not directory handles. it just might work on directory handles, too. >Below is my code, and advice would be appreciated. > [...] ># open folder >opendir C_DRIVE, $folder or die "problem reading $folder: $!"; > >my @files = grep { -f "$folder/$_" } readdir(C_DRIVE); # all >files >my @folders = grep { -d "$folder/$_" } readdir(C_DRIVE); # all >folders However a better approach would be to loop through all the files in a single pass and assign them to @files or @folders as you read each directory entry. <sketch only, not actual code> while (my $direntry = readdir (C_DRIVE)) if (-f $direntry) {push @files, $direntry}; if (-d $direntry) {push @folders, $direntry} } Or read then all into a one array, duplicate that array, and then filter @folders = @files = readdir(...); @folders = grep (-d ...., @folders); @files = grep (-f ...., @files); jue > ># close folder >closedir C_DRIVE; > ># test results >print "your files: @files\n"; >print "your folders: @folders\n"; >
From: Patrick H. on 16 Feb 2010 00:43 On Feb 15, 11:26 pm, "Patrick H." <patri...(a)gmail.com> wrote: > Hi, I am toying around with the directory operations chapter of > "Learning Perl" and ran into a bit of a snag. > > I am trying to open a directory, output all the -f files to a @files > array and all the -d files to a @folders array. The problem is it > seems to only work for the first instance of readdir I use; they both > work individually when I comment the other out, but when I have them > both only the first array is populated. Do I need to closedir and then > opendir again, or is there a way for me to reset the cursor (if that > is even the right terminology)? > > Below is my code, and advice would be appreciated. > > Patrick H. > > #!/usr/bin/perl -w > use strict; > > # folder to scan > my $folder = 'c:/'; > > # open folder > opendir C_DRIVE, $folder or die "problem reading $folder: $!"; > > my @files = grep { -f "$folder/$_" } readdir(C_DRIVE); # all > files > my @folders = grep { -d "$folder/$_" } readdir(C_DRIVE); # all > folders > > # close folder > closedir C_DRIVE; > > # test results > print "your files: @files\n"; > print "your folders: @folders\n"; With the risk of looking like I'm talking to myself, I came up with a different way of doing it through just one readdir - figured I would post what my solution ended up being. -Patrick # scope variables my (@files,@folders); # read directory while (my $name = readdir C_DRIVE) { push @files, $name if -f "$folder/$name"; push @folders, $name if -d "$folder/$name"; }
From: Patrick H. on 16 Feb 2010 00:48 On Feb 15, 11:42 pm, Jürgen Exner <jurge...(a)hotmail.com> wrote: > However a better approach would be to loop through all the files in a > single pass and assign them to @files or @folders as you read each > directory entry. > > <sketch only, not actual code> > > while (my $direntry = readdir (C_DRIVE)) > if (-f $direntry) {push @files, $direntry}; > if (-d $direntry) {push @folders, $direntry} > } Jue, thank you very much for the input. I came up with a similar approach before I read your post. Always glad to have someone else's opinion confirm what I was thinking :) . Thanks, Patrick
From: John W. Krahn on 16 Feb 2010 02:35 Patrick H. wrote: > Hi, I am toying around with the directory operations chapter of > "Learning Perl" and ran into a bit of a snag. > > I am trying to open a directory, output all the -f files to a @files > array and all the -d files to a @folders array. The problem is it > seems to only work for the first instance of readdir I use; they both > work individually when I comment the other out, but when I have them > both only the first array is populated. Do I need to closedir and then > opendir again, or is there a way for me to reset the cursor (if that > is even the right terminology)? perldoc -f rewinddir > Below is my code, and advice would be appreciated. > > Patrick H. > > > #!/usr/bin/perl -w > use strict; > > # folder to scan > my $folder = 'c:/'; > > # open folder > opendir C_DRIVE, $folder or die "problem reading $folder: $!"; > > my @files = grep { -f "$folder/$_" } readdir(C_DRIVE); # all > files > my @folders = grep { -d "$folder/$_" } readdir(C_DRIVE); # all > folders my ( @files, @folders ); while ( my $file = readdir C_DRIVE ) { push @files if -f "$folder/$file"; push @folders if -d "$folder/$file"; } > # close folder > closedir C_DRIVE; > > # test results > print "your files: @files\n"; > print "your folders: @folders\n"; John -- The programmer is fighting against the two most destructive forces in the universe: entropy and human stupidity. -- Damian Conway
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