File::Basename doc overhaul

Message-ID: <20050706031127.GL9227@windhund.schwern.org>

(with some minor changes)

p4raw-id: //depot/perl@25086

1 files changed, 156 insertions, 143 deletions

diff --git a/lib/File/Basename.pm b/lib/File/Basename.pm
index 887c7bae4a..e6b16e7503 100644
--- a/lib/File/Basename.pm
+++ b/lib/File/Basename.pm
@@ -1,12 +1,6 @@
-package File::Basename;
-
 =head1 NAME
 
-fileparse - split a pathname into pieces
-
-basename - extract just the filename from a path
-
-dirname - extract just the directory from a path
+File::Basename - Parse file paths into directory, filename and suffix.
 
 =head1 SYNOPSIS
 
@@ -14,120 +8,25 @@ dirname - extract just the directory from a path
 
     ($name,$path,$suffix) = fileparse($fullname,@suffixlist);
     $name = fileparse($fullname,@suffixlist);
-    fileparse_set_fstype($os_string);
+
     $basename = basename($fullname,@suffixlist);
-    $dirname = dirname($fullname);
+    $dirname  = dirname($fullname);
 
-    ($name,$path,$suffix) = fileparse("lib/File/Basename.pm",qr{\.pm});
-    fileparse_set_fstype("VMS");
-    $basename = basename("lib/File/Basename.pm",".pm");
-    $dirname = dirname("lib/File/Basename.pm");
 
 =head1 DESCRIPTION
 
-These routines allow you to parse file specifications into useful
-pieces using the syntax of different operating systems.
-
-=over 4
-
-=item fileparse_set_fstype
-
-You select the syntax via the routine fileparse_set_fstype().
-
-If the argument passed to it contains one of the substrings
-"VMS", "MSDOS", "MacOS", "AmigaOS" or "MSWin32", the file specification 
-syntax of that operating system is used in future calls to 
-fileparse(), basename(), and dirname().  If it contains none of
-these substrings, Unix syntax is used.  This pattern matching is
-case-insensitive.  If you've selected VMS syntax, and the file
-specification you pass to one of these routines contains a "/",
-they assume you are using Unix emulation and apply the Unix syntax
-rules instead, for that function call only.
-
-If the argument passed to it contains one of the substrings "VMS",
-"MSDOS", "MacOS", "AmigaOS", "os2", "MSWin32" or "RISCOS", then the pattern
-matching for suffix removal is performed without regard for case,
-since those systems are not case-sensitive when opening existing files
-(though some of them preserve case on file creation).
-
-If you haven't called fileparse_set_fstype(), the syntax is chosen
-by examining the builtin variable C<$^O> according to these rules.
-
-=item fileparse
-
-The fileparse() routine divides a file specification into three
-parts: a leading B<path>, a file B<name>, and a B<suffix>.  The
-B<path> contains everything up to and including the last directory
-separator in the input file specification.  The remainder of the input
-file specification is then divided into B<name> and B<suffix> based on
-the optional patterns you specify in C<@suffixlist>.  Each element of
-this list can be a qr-quoted pattern (or a string which is interpreted
-as a regular expression), and is matched
-against the end of B<name>.  If this succeeds, the matching portion of
-B<name> is removed and prepended to B<suffix>.  By proper use of
-C<@suffixlist>, you can remove file types or versions for examination.
-
-You are guaranteed that if you concatenate B<path>, B<name>, and
-B<suffix> together in that order, the result will denote the same
-file as the input file specification.
-
-In scalar context, fileparse() returns only the B<name> part of the filename.
-
-=back
-
-=head1 EXAMPLES
-
-Using Unix file syntax:
-
-    ($base,$path,$type) = fileparse('/virgil/aeneid/draft.book7',
-				    qr{\.book\d+});
-
-would yield
-
-    $base eq 'draft'
-    $path eq '/virgil/aeneid/',
-    $type eq '.book7'
-
-Similarly, using VMS syntax:
-
-    ($name,$dir,$type) = fileparse('Doc_Root:[Help]Rhetoric.Rnh',
-				   qr{\..*});
-
-would yield
-
-    $name eq 'Rhetoric'
-    $dir  eq 'Doc_Root:[Help]'
-    $type eq '.Rnh'
-
-=over
-
-=item C<basename>
-
-The basename() routine returns the first element of the list produced
-by calling fileparse() with the same arguments, except that it always
-quotes metacharacters in the given suffixes.  It is provided for
-programmer compatibility with the Unix shell command basename(1).
-
-=item C<dirname>
-
-The dirname() routine returns the directory portion of the input file
-specification.  When using VMS or MacOS syntax, this is identical to the
-second element of the list produced by calling fileparse() with the same
-input file specification.  (Under VMS, if there is no directory information
-in the input file specification, then the current default device and
-directory are returned.)  When using Unix or MSDOS syntax, the return
-value conforms to the behavior of the Unix shell command dirname(1).  This
-is usually the same as the behavior of fileparse(), but differs in some
-cases.  For example, for the input file specification F<lib/>, fileparse()
-considers the directory name to be F<lib/>, while dirname() considers the
-directory name to be F<.>).
+These routines allow you to parse file paths into their directory, filename
+and suffix.
 
-=back
+B<NOTE>: C<dirname()> and C<basename()> emulate the behaviours, and quirks, of
+the shell and C functions of the same name.  See each function's documention
+for details.
 
 =cut
 
 
-## use strict;
+package File::Basename;
+
 # A bit of juggling to insure that C<use re 'taint';> always works, since
 # File::Basename is used during the Perl build, when the re extension may
 # not be available.
@@ -138,7 +37,7 @@ BEGIN {
 }
 
 
-
+use strict;
 use 5.006;
 use warnings;
 our(@ISA, @EXPORT, $VERSION, $Fileparse_fstype, $Fileparse_igncase);
@@ -147,25 +46,49 @@ require Exporter;
 @EXPORT = qw(fileparse fileparse_set_fstype basename dirname);
 $VERSION = "2.73";
 
+fileparse_set_fstype($^O);
 
-#   fileparse_set_fstype() - specify OS-based rules used in future
-#                            calls to routines in this package
-#
-#   Currently recognized values: VMS, MSDOS, MacOS, AmigaOS, os2, RISCOS
-#       Any other name uses Unix-style rules and is case-sensitive
 
-sub fileparse_set_fstype {
-  my @old = ($Fileparse_fstype, $Fileparse_igncase);
-  if (@_) {
-    $Fileparse_fstype = $_[0];
-    $Fileparse_igncase = ($_[0] =~ /^(?:MacOS|VMS|AmigaOS|os2|RISCOS|MSWin32|MSDOS)/i);
-  }
-  wantarray ? @old : $old[0];
-}
+=over 4
+
+=item C<fileparse>
+
+    my($filename, $directories, $suffix) = fileparse($path);
+    my($filename, $directories, $suffix) = fileparse($path, @suffixes);
+    my $filename                         = fileparse($path, @suffixes);
+
+The C<fileparse()> routine divides a file path into its $directories, $filename
+and (optionally) the filename $suffix.
+
+$directories contains everything up to and including the last
+directory separator in the $path including the volume (if applicable).
+The remainder of the $path is the $filename.
+
+     # On Unix returns ("baz", "/foo/bar/", "")
+     fileparse("/foo/bar/baz");
+
+     # On Windows returns ("baz", "C:\foo\bar\", "")
+     fileparse("C:\foo\bar\baz");
+
+     # On Unix returns ("", "/foo/bar/baz/", "")
+     fileparse("/foo/bar/baz/");
+
+If @suffixes are given each element is a pattern (either a string or a
+C<qr//>) matched against the end of the $filename.  The matching
+portion is removed and becomes the $suffix.
+
+     # On Unix returns ("baz", "/foo/bar", ".txt")
+     fileparse("/foo/bar/baz", qr/\.[^.]*/);
+
+If type is one of "VMS", "MSDOS", "MacOS", "AmigaOS", "OS2", "MSWin32"
+or "RISCOS" (see C<fileparse_set_fstype()>) then the pattern matching
+for suffix removal is performed case-insensitively, since those
+systems are not case-sensitive when opening existing files.
+
+You are guaranteed that C<$directories . $filename . $suffix> will
+denote the same location as the original $path.
 
-#   fileparse() - parse file specification
-#
-#   Version 2.4  27-Sep-1996  Charles Bailey  bailey@genetics.upenn.edu
+=cut
 
 
 sub fileparse {
@@ -227,13 +150,31 @@ sub fileparse {
     }
   }
 
+  # Ensure taint is propgated from the path to its pieces.
   $tail .= $taint if defined $tail; # avoid warning if $tail == undef
   wantarray ? ($basename .= $taint, $dirpath .= $taint, $tail)
             : ($basename .= $taint);
 }
 
 
-#   basename() - returns first element of list returned by fileparse()
+
+=item C<basename>
+
+    my $filename = basename($path);
+    my $filename = basename($path, @suffixes);
+
+C<basename()> works just like C<fileparse()> in scalar context - you only get
+the $filename - except that it always quotes metacharacters in the @suffixes.
+
+    # These two function calls are equivalent.
+    my $filename = basename("/foo/bar/baz.txt",  ".txt");
+    my $filename = fileparse("/foo/bar/baz.txt", qr/\Q.txt\E/);
+
+This function is provided for compatibility with the Unix shell command 
+C<basename(1)>.
+
+=cut
+
 
 sub basename {
   my($name) = shift;
@@ -241,22 +182,64 @@ sub basename {
 }
 
 
-#    dirname() - returns device and directory portion of file specification
-#        Behavior matches that of Unix dirname(1) exactly for Unix and MSDOS
-#        filespecs except for names ending with a separator, e.g., "/xx/yy/".
-#        This differs from the second element of the list returned
-#        by fileparse() in that the trailing '/' (Unix) or '\' (MSDOS) (and
-#        the last directory name if the filespec ends in a '/' or '\'), is lost.
+
+=item C<dirname>
+
+This function is provided for compatibility with the Unix shell
+command C<dirname(1)> and has inherited some of its quirks.  In spite of
+its name it does B<NOT> always return the directory name as you might
+expect.  To be safe, if you want the directory name of a path use
+C<fileparse()>.
+
+    # On all but Unix and MSDOS
+    my $directories = dirname($path);
+
+On all system types but Unix and MSDOS this works just like
+C<fileparse($path)> but returning just the $directories.
+
+    # On Unix and MSDOS
+    my $path_one_level_up = dirname($path);
+
+When using Unix or MSDOS syntax this emulates the C<dirname(1)> shell function
+which is subtly different from how C<fileparse()> works.  It returns all but
+the last level of a file path even if the last level is clearly a directory.
+In effect, it is not returning the directory portion but simply the path one
+level up acting like C<chop()> for file paths.
+
+Also unlike C<fileparse()>, C<dirname()> does not include a trailing slash on
+its returned path.
+
+    # returns /foo/bar.  fileparse() would return /foo/bar/
+    dirname("/foo/bar/baz");
+
+    # also returns /foo/bar despite the fact that baz is clearly a 
+    # directory.  fileparse() would return /foo/bar/baz/
+    dirname("/foo/bar/baz/");
+
+    # returns '.'.  fileparse() would return 'foo/'
+    dirname("foo/");
+
+Under VMS, if there is no directory information in the $path, then the
+current default device and directory is used.
+
+=cut
+
 
 sub dirname {
-    my($basename,$dirname) = fileparse($_[0]);
     my($fstype) = $Fileparse_fstype;
 
+    if( $fstype =~ /VMS/i and $_[0] =~ m{/} ) {
+        # Parse as Unix
+        local($File::Basename::Fileparse_fstype) = '';
+        return dirname(@_);
+    }
+
+    my($basename,$dirname) = fileparse($_[0]);
+
     if ($fstype =~ /VMS/i) { 
-        if ($_[0] =~ m#/#) { $fstype = '' }
-        else { return $dirname || $ENV{DEFAULT} }
+        $dirname ||= $ENV{DEFAULT};
     }
-    if ($fstype =~ /MacOS/i) {
+    elsif ($fstype =~ /MacOS/i) {
 	if( !length($basename) && $dirname !~ /^[^:]+:\z/) {
 	    $dirname =~ s/([^:]):\z/$1/s;
 	    ($basename,$dirname) = fileparse $dirname;
@@ -276,17 +259,47 @@ sub dirname {
         $dirname =~ s#[^:/]+\z## unless length($basename);
     }
     else {
-        $dirname =~ s:(.)/*\z:$1:s;
+        $dirname =~ s{(.)/*\z}{$1}s;
         unless( length($basename) ) {
-	    local($File::Basename::Fileparse_fstype) = $fstype;
 	    ($basename,$dirname) = fileparse $dirname;
-	    $dirname =~ s:(.)/*\z:$1:s;
+	    $dirname =~ s{(.)/*\z}{$1}s;
 	}
     }
 
     $dirname;
 }
 
-fileparse_set_fstype $^O;
+
+=item C<fileparse_set_fstype>
+
+  my $previous_fstype = fileparse_set_fstype($type);
+
+Normally File::Basename will assume a file path type native to your current
+operating system (ie. /foo/bar style on Unix, \foo\bar on Windows, etc...).
+With this function you can override that assumption.
+
+Valid $types are "VMS", "MSDOS", "MacOS", "AmigaOS", "OS2", "RISCOS",
+"MSWin32" and "Unix" (case-insensitive).  If an unrecognized $type is
+given Unix semantics will be assumed.
+
+If you've selected VMS syntax, and the file specification you pass to
+one of these routines contains a "/", they assume you are using Unix
+emulation and apply the Unix syntax rules instead, for that function
+call only.
+
+=back
+
+=cut
+
+
+sub fileparse_set_fstype {
+  my @old = ($Fileparse_fstype, $Fileparse_igncase);
+  if (@_) {
+    $Fileparse_fstype = $_[0];
+    $Fileparse_igncase = ($_[0] =~ /^(?:MacOS|VMS|AmigaOS|os2|RISCOS|MSWin32|MSDOS)/i);
+  }
+  wantarray ? @old : $old[0];
+}
+
 
 1;