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.
DISCLAIMER OF WARRANTY¶
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