Provided by: libfile-save-home-perl_0.09-2_all 
NAME
File::Save::Home - Place file safely under user home directory
VERSION
This document refers to version 0.09, released December 14, 2012.
SYNOPSIS
use File::Save::Home qw(
get_home_directory
get_subhome_directory_status
make_subhome_directory
restore_subhome_directory_status
conceal_target_file
reveal_target_file
make_subhome_temp_directory
);
$home_dir = get_home_directory();
$desired_dir_ref = get_subhome_directory_status("desired/directory");
$desired_dir_ref = get_subhome_directory_status(
"desired/directory",
"pseudohome/directory", # two-argument version
);
$desired_dir = make_subhome_directory($desired_dir_ref);
restore_subhome_directory_status($desired_dir_ref);
$target_ref = conceal_target_file( {
dir => $desired_dir,
file => 'file_to_be_checked',
test => 0,
} );
reveal_target_file($target_ref);
$tmpdir = make_subhome_temp_directory();
$tmpdir = make_subhome_temp_directory(
"pseudohome/directory", # optional argument version
);
DESCRIPTION
In the course of deploying an application on another user's system, you sometimes need to
place a file in or underneath that user's home directory. Can you do so safely?
This Perl extension provides several functions which try to determine whether you can,
indeed, safely create directories and files underneath a user's home directory. Among
other things, if you are placing a file in such a location only temporarily -- say, for
testing purposes -- you can temporarily hide any already existing file with the same name
and restore it to its original name and timestamps when you are done.
USAGE
"get_home_directory()"
Analyzes environmental information to determine whether there exists on the system a
'HOME' or 'home-equivalent' directory. Takes no arguments. Returns that directory if it
exists; "croak"s otherwise.
On Win32, this directory is the one returned by the following function from the
Win32module:
Win32->import( qw(CSIDL_LOCAL_APPDATA) );
$realhome = Win32::GetFolderPath( CSIDL_LOCAL_APPDATA() );
... which translates to something like C:\Documents and Settings\localuser\Local
Settings\Application Data. (For a further discussion of Win32, see below "SEE ALSO".)
On Unix-like systems, things are much simpler. We simply check the value of $ENV{HOME}.
We cannot do that on Win32 because $ENV{HOME} is not defined there.
"get_subhome_directory_status()"
Single argument version
Takes as argument a string holding the name of a directory, either single-level ("mydir")
or multi-level ("path/to/mydir"). Determines whether that directory already exists
underneath the user's home or home-equivalent directory. Calls "get_home_directory()"
internally, then tacks on the path passed as argument.
Two-argument version
Suppose you want to determine the name of a user's home directory by some other route than
"get_home_directory()". Suppose, for example, that you're on Win32 and want to use the
"my_home()" method supplied by CPAN distribution File::HomeDir -- a method which returns a
different result from that of our "get_home_directory()" -- but you still want to use
those File::Save::Home functions which normally call "get_home_directory()" internally.
Or, suppose you want to supply an arbitrary path.
You can now do so by supplying an optional second argument to
"get_subhome_directory_status". This argument should be a valid path name for a directory
to which you have write privileges. "get_subhome_directory_status" will determine if the
directory exists and, if so, determine whether the first argument is a subdirectory of the
second argument.
Both versions
Whether you use the single argument version or the two-argument version,
"get_subhome_directory_status" returns a reference to a four-element hash whose keys are:
home
The absolute path of the home directory.
abs The absolute path of the specified directory.
flag
A Boolean value indicating whether that directory already exists (a true value) or not
("undef").
top The uppermost subdirectory passed as the argument to this function.
"make_subhome_directory()"
Takes as argument the hash reference returned by "get_subhome_directory_status()".
Examines the first element in that array -- the directory name -- and creates the
directory if it doesn't already exist. The function "croak"s if the directory cannot be
created.
"restore_subhome_directory_status()"
Undoes "make_subhome_directory()", i.e., if there was no specified directory under the
user's home directory on the user's system before testing, any such directory created
during testing is removed. On the other hand, if there was such a directory present
before testing, it is left unchanged.
"make_subhome_temp_directory()"
Regular version: no arguments
Creates a randomly named temporary directory underneath the home or home-equivalent
directory returned by "get_home_directory()".
Optional argument version
Creates a randomly named temporary directory underneath the directory supplied as the
single argument. This version is analogous to the two-argument verion of
"get_subhome_directory_status()" above. You could use it if, for example, you wanted to
use "File::HomeDir-"my_home()> to supply a value for the user's home directory instead of
our "get_home_directory()".
Both versions
In both versions, the temporary subdirectory is created by calling "File::Temp::tempdir
(DIR =" $home, CLEANUP => 1)>. The function returns the directory path if successful;
"croak"s otherwise.
Note: Any temporary directory so created remains in existence for the duration of the
program, but is deleted (along with all its contents) when the program exits.
"conceal_target_file()"
Determines whether file with specified name already exists in specified directory and, if
so, temporarily hides it by renaming it with a .hidden suffix and storing away its last
access and modification times. Takes as argument a reference to a hash with these keys:
dir The directory in which the file is presumed to exist.
file
The targeted file, i.e., the file to be temporarily hidden if it already exists.
test
Boolean value which, if turned on (1), will cause the function, when called, to run
two "Test::More::ok()" tests. Defaults to off (0).
Returns a reference to a hash with these keys:
full
The absolute path to the target file.
hidden
The absolute path to the now-hidden file.
atime
The last access time to the target file ("(stat($file{full}))[8]").
modtime
The last modification time to the target file ("(stat($file{full}))[9]").
test
The value of the key "test" in the hash passed by reference as an argument to this
function.
"reveal_target_file()"
Used in conjunction with "conceal_target_file()" to restore the original status of the
file targeted by "conceal_target_file()", i.e., renames the hidden file to its original
name by removing the .hidden suffix, thereby deleting any other file with the original
name created between the calls tothe two functions. "croak"s if the hidden file cannot be
renamed. Takes as argument the hash reference returned by "conceal_target_file()". If
the value for the "test" key in the hash passed as an argument to "conceal_target_file()"
was true, then a call to "reveal_target_file" will run three "Test::More::ok()" tests.
BUGS AND TODO
So far tested only on Unix-like systems and Win32.
SEE ALSO
perl(1). ExtUtils::ModuleMaker::Auxiliary. ExtUtils::ModuleMaker::Utility. The latter
two packages are part of the ExtUtils::ModuleMaker distribution available from the same
author on CPAN. They and the ExtUtils::ModuleMaker test suite provide examples of the use
of File::Save::Home.
Two other distributions located on CPAN, File::HomeDir and File::HomeDir::Win32, may also
be used to locate a suitable value for a user's home directory. It should be noted,
however, that those modules and File::Save::Home each take a different approach to
defining a home directory on Win32 systems. Hence, each may deliver a different result on
a given system. I cannot say that one distribution's approach is any more or less correct
than the other two's approaches. The following comments should be viewed as my subjective
impressions; YMMV.
File::HomeDir was originally written by Sean M Burke and is now maintained by Adam
Kennedy. As of version 0.52 its interface provides three methods for the ''current
user'':
$home = File::HomeDir->my_home;
$docs = File::HomeDir->my_documents;
$data = File::HomeDir->my_data;
When I ran these three methods on a Win2K Pro system running ActivePerl 8, I got these
results:
C:\WINNT\system32>perl -MFile::HomeDir -e "print File::HomeDir->my_home"
C:\Documents and Settings\localuser
C:\WINNT\system32>perl -MFile::HomeDir -e "print File::HomeDir->my_documents"
C:\Documents and Settings\localuser\My Documents
C:\WINNT\system32>perl -MFile::HomeDir -e "print File::HomeDir->my_data"
C:\Documents and Settings\localuser\Local Settings\Application Data
In contrast, when I ran the closest equivalent method in File::Save::Home,
"get_home_directory", I got this result:
C:\WINNT\system32>perl -MFile::Save::Home -e "print File::Save::Home->get_home_directory"
C:\Documents and Settings\localuser\Local Settings\Application Data
In other words, "File::Save::Home->get_home_directory" gave the same result as
"File::HomeDir->my_data", not, as I might have expected, the same result as
"File::HomeDir->my_home".
These results can be explained by peeking behind the curtains and looking at the source
code for each module.
File::HomeDir
File::HomeDir's objective is to provide a value for a user's home directory on a wide
variety of operating systems. When invoked, it detects the operating system you're on and
calls a subclassed module. When used on a Win32 system, that subclass is called
File::HomeDir::Windows (not to be confused with the separate CPAN distribution
File::HomeDir::Win32). "File::HomeDir::Windows->my_home()" looks like this:
sub my_home {
my $class = shift;
if ( $ENV{USERPROFILE} ) { return $ENV{USERPROFILE}; }
if ( $ENV{HOMEDRIVE} and $ENV{HOMEPATH} ) {
return File::Spec->catpath( $ENV{HOMEDRIVE}, $ENV{HOMEPATH}, '',);
}
Carp::croak("Could not locate current user's home directory");
}
In other words, determine the current user's home directory simply by checking
environmental variables analogous to the $ENV{HOME} on Unix-like systems. A very
straightforward approach!
As mentioned above, File::Save::Home takes a different approach. It uses the Win32 module
to, in effect, check a particular key in the registry.
Win32->import( qw(CSIDL_LOCAL_APPDATA) );
$realhome = Win32::GetFolderPath( CSIDL_LOCAL_APPDATA() );
This approach was suggested to me in August 2005 by several members of Perlmonks. (See
threads Installing a config file during module operation
(<http://perlmonks.org/?node_id=481690>) and Win32 CSIDL_LOCAL_APPDATA
(<http://perlmonks.org/?node_id=485902>).) I adopted this approach in part because the
people recommending it knew more about Windows than I did, and in part because
File::HomeDir was not quite as mature as it has since become.
But don't trust me; trust Microsoft! Here's their explanation for the use of CSIDL values
in general and CSIDL_LOCAL_APPDATA() in particular:
• CSIDL values provide a unique system-independent way to identify special folders used
frequently by applications, but which may not have the same name or location on any
given system. For example, the system folder may be ''C:\Windows'' on one system and
''C:\Winnt'' on another. These constants are defined in Shlobj.h and Shfolder.h.
• CSIDL_LOCAL_APPDATA (0x001c) Version 5.0. The file system directory that serves as a
data repository for local (nonroaming) applications. A typical path is C:\Documents
and Settings\username\Local Settings\Application Data.
(Source:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/shellcc/platform/shell/reference/enums/csidl.asp
<http://msdn.microsoft.com/library/default.asp?url=/library/en-
us/shellcc/platform/shell/reference/enums/csidl.asp>. Link valid as of Feb 18 2006.
Thanks to Soren Andersen for reminding me of this citation.)
It is interesting that the other two File::HomeDir methods listed above, "my_documents()"
and "my_data()" both rely on using a Win32 module to peer into the registry, albeit in a
slightly different manner from "File::Save::Home->get_home_directory". TIMTOWTDI.
In an event, File::Save::Home has a number of useful methods besides
"get_home_directory()" which merit your consideration. And, as noted above, you can
supply any valid directory as an optional additional argument to the two File::Save::Home
functions which normally default to calling "get_home_directory" internally.
File::HomeDir::Win32
File::HomeDir::Win32 was originally written by Rob Rothenberg and is now maintained by
Randy Kobes. According to Adam Kennedy
(http://annocpan.org/~JKEENAN/File-Save-Home-0.07/lib/File/Save/Home.pm#note_636
<http://annocpan.org/~JKEENAN/File-Save-Home-0.07/lib/File/Save/Home.pm#note_636>), ''The
functionality in File::HomeDir::Win32 is gradually being merged into File::HomeDir over
time and will eventually be deprecated (although left in place for compatibility
purposes).'' Because I have not yet fully installed File::HomeDir::Win32, I will defer
further comparison between it and File::Save::Home to a later date.
AUTHOR
James E Keenan
CPAN ID: JKEENAN
jkeenan@cpan.org
http://search.cpan.org/~jkeenan
ACKNOWLEDGMENTS
File::Save::Home has its origins in the maintenance revisions I was doing on CPAN
distribution ExtUtils::ModuleMaker in the summer of 2005. After I made a presentation
about that distribution to the Toronto Perlmongers on October 27, 2005, Michael Graham
suggested that certain utility functions could be extracted to a separate Perl extension
for more general applicability. This module is the implementation of Michael's
suggestion.
While I was developing those utility functions for ExtUtils::ModuleMaker, I turned to the
Perlmonks for assistance with the problem of determining a suitable value for the user's
home directory on Win32 systems. In the Perlmonks discussion threads referred to above I
received helpful suggestions from monks CountZero, Tanktalus, xdg and holli, among others.
Thanks to Rob Rothenberg for prodding me to expand the SEE ALSO section and to Adam
Kennedy for responding to questions about File::HomeDir.
COPYRIGHT
Copyright (c) 2005-06 James E. Keenan. United States. All rights reserved.
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
The full text of the license can be found in the LICENSE file included with this module.
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