File::Fetch(3pm) Perl Programmers Reference Guide File::Fetch(3pm)
NAME
File::Fetch - A generic file fetching mechanism
SYNOPSIS
use File::Fetch;
### build a File::Fetch object ###
my $ff = File::Fetch->new(uri => 'http://some.where.com/dir/a.txt');
### fetch the uri to cwd() ###
my $where = $ff->fetch() or die $ff->error;
### fetch the uri to /tmp ###
my $where = $ff->fetch( to => '/tmp' );
### parsed bits from the uri ###
$ff->uri;
$ff->scheme;
$ff->host;
$ff->path;
$ff->file;
DESCRIPTION
File::Fetch is a generic file fetching mechanism.
It allows you to fetch any file pointed to by a "ftp", "http", "file",
"git" or "rsync" uri by a number of different means.
See the "HOW IT WORKS" section further down for details.
ACCESSORS
A "File::Fetch" object has the following accessors
$ff->uri
The uri you passed to the constructor
$ff->scheme
The scheme from the uri (like 'file', 'http', etc)
$ff->host
The hostname in the uri. Will be empty if host was originally
'localhost' for a 'file://' url.
$ff->vol
On operating systems with the concept of a volume the second
element of a file:// is considered to the be volume specification
for the file. Thus on Win32 this routine returns the volume, on
other operating systems this returns nothing.
On Windows this value may be empty if the uri is to a network
share, in which case the 'share' property will be defined.
Additionally, volume specifications that use '|' as ':' will be
converted on read to use ':'.
On VMS, which has a volume concept, this field will be empty
because VMS file specifications are converted to absolute UNIX
format and the volume information is transparently included.
$ff->share
On systems with the concept of a network share (currently only
Windows) returns the sharename from a file://// url. On other
operating systems returns empty.
$ff->path
The path from the uri, will be at least a single '/'.
$ff->file
The name of the remote file. For the local file name, the result of
$ff->output_file will be used.
$ff->file_default
The name of the default local file, that $ff->output_file falls
back to if it would otherwise return no filename. For example when
fetching a URI like http://www.abc.net.au/ the contents retrieved
may be from a remote file called 'index.html'. The default value of
this attribute is literally 'file_default'.
$ff->output_file
The name of the output file. This is the same as $ff->file, but any
query parameters are stripped off. For example:
http://example.com/index.html?x=y
would make the output file be "index.html" rather than
"index.html?x=y".
METHODS
$ff = File::Fetch->new( uri => 'http://some.where.com/dir/file.txt' );
Parses the uri and creates a corresponding File::Fetch::Item object,
that is ready to be "fetch"ed and returns it.
Returns false on failure.
$where = $ff->fetch( [to => /my/output/dir/ | \$scalar] )
Fetches the file you requested and returns the full path to the file.
By default it writes to cwd(), but you can override that by specifying
the "to" argument:
### file fetch to /tmp, full path to the file in $where
$where = $ff->fetch( to => '/tmp' );
### file slurped into $scalar, full path to the file in $where
### file is downloaded to a temp directory and cleaned up at exit time
$where = $ff->fetch( to => \$scalar );
Returns the full path to the downloaded file on success, and false on
failure.
$ff->error([BOOL])
Returns the last encountered error as string. Pass it a true value to
get the Carp::longmess() output instead.
HOW IT WORKS
File::Fetch is able to fetch a variety of uris, by using several
external programs and modules.
Below is a mapping of what utilities will be used in what order for
what schemes, if available:
file => LWP, lftp, file
http => LWP, HTTP::Tiny, wget, curl, lftp, fetch, HTTP::Lite, lynx, iosock
ftp => LWP, Net::FTP, wget, curl, lftp, fetch, ncftp, ftp
rsync => rsync
git => git
If you'd like to disable the use of one or more of these utilities
and/or modules, see the $BLACKLIST variable further down.
If a utility or module isn't available, it will be marked in a cache
(see the $METHOD_FAIL variable further down), so it will not be tried
again. The "fetch" method will only fail when all options are
exhausted, and it was not able to retrieve the file.
The "fetch" utility is available on FreeBSD. NetBSD and Dragonfly BSD
may also have it from "pkgsrc". We only check for "fetch" on those
three platforms.
"iosock" is a very limited IO::Socket::INET based mechanism for
retrieving "http" schemed urls. It doesn't follow redirects for
instance.
"git" only supports "git://" style urls.
A special note about fetching files from an ftp uri:
By default, all ftp connections are done in passive mode. To change
that, see the $FTP_PASSIVE variable further down.
Furthermore, ftp uris only support anonymous connections, so no named
user/password pair can be passed along.
"/bin/ftp" is blacklisted by default; see the $BLACKLIST variable
further down.
GLOBAL VARIABLES
The behaviour of File::Fetch can be altered by changing the following
global variables:
$File::Fetch::FROM_EMAIL
This is the email address that will be sent as your anonymous ftp
password.
Default is "File-Fetch@example.com".
$File::Fetch::USER_AGENT
This is the useragent as "LWP" will report it.
Default is "File::Fetch/$VERSION".
$File::Fetch::FTP_PASSIVE
This variable controls whether the environment variable "FTP_PASSIVE"
and any passive switches to commandline tools will be set to true.
Default value is 1.
Note: When $FTP_PASSIVE is true, "ncftp" will not be used to fetch
files, since passive mode can only be set interactively for this binary
$File::Fetch::TIMEOUT
When set, controls the network timeout (counted in seconds).
Default value is 0.
$File::Fetch::WARN
This variable controls whether errors encountered internally by
"File::Fetch" should be "carp"'d or not.
Set to false to silence warnings. Inspect the output of the error()
method manually to see what went wrong.
Defaults to "true".
$File::Fetch::DEBUG
This enables debugging output when calling commandline utilities to
fetch files. This also enables "Carp::longmess" errors, instead of the
regular "carp" errors.
Good for tracking down why things don't work with your particular
setup.
Default is 0.
$File::Fetch::BLACKLIST
This is an array ref holding blacklisted modules/utilities for fetching
files with.
To disallow the use of, for example, "LWP" and "Net::FTP", you could
set $File::Fetch::BLACKLIST to:
$File::Fetch::BLACKLIST = [qw|lwp netftp|]
The default blacklist is [qw|ftp|], as "/bin/ftp" is rather unreliable.
See the note on "MAPPING" below.
$File::Fetch::METHOD_FAIL
This is a hashref registering what modules/utilities were known to fail
for fetching files (mostly because they weren't installed).
You can reset this cache by assigning an empty hashref to it, or
individually remove keys.
See the note on "MAPPING" below.
MAPPING
Here's a quick mapping for the utilities/modules, and their names for
the $BLACKLIST, $METHOD_FAIL and other internal functions.
LWP => lwp
HTTP::Lite => httplite
HTTP::Tiny => httptiny
Net::FTP => netftp
wget => wget
lynx => lynx
ncftp => ncftp
ftp => ftp
curl => curl
rsync => rsync
lftp => lftp
fetch => fetch
IO::Socket => iosock
FREQUENTLY ASKED QUESTIONS
So how do I use a proxy with File::Fetch?
"File::Fetch" currently only supports proxies with LWP::UserAgent. You
will need to set your environment variables accordingly. For example,
to use an ftp proxy:
$ENV{ftp_proxy} = 'foo.com';
Refer to the LWP::UserAgent manpage for more details.
I used 'lynx' to fetch a file, but its contents is all wrong!
"lynx" can only fetch remote files by dumping its contents to "STDOUT",
which we in turn capture. If that content is a 'custom' error file
(like, say, a "404 handler"), you will get that contents instead.
Sadly, "lynx" doesn't support any options to return a different exit
code on non-"200 OK" status, giving us no way to tell the difference
between a 'successful' fetch and a custom error page.
Therefor, we recommend to only use "lynx" as a last resort. This is why
it is at the back of our list of methods to try as well.
Files I'm trying to fetch have reserved characters or non-ASCII characters
in them. What do I do?
"File::Fetch" is relatively smart about things. When trying to write a
file to disk, it removes the "query parameters" (see the "output_file"
method for details) from the file name before creating it. In most
cases this suffices.
If you have any other characters you need to escape, please install the
"URI::Escape" module from CPAN, and pre-encode your URI before passing
it to "File::Fetch". You can read about the details of URIs and URI
encoding here:
<https://datatracker.ietf.org/doc/html/rfc2396>
TODO
Implement $PREFER_BIN
To indicate to rather use commandline tools than modules
BUG REPORTS
Please report bugs or other issues to <bug-file-fetch@rt.cpan.org<gt>.
AUTHOR
This module by Jos Boumans <kane@cpan.org>.
COPYRIGHT
This library is free software; you may redistribute and/or modify it
under the same terms as Perl itself.
perl v5.38.2 2023-11-28 File::Fetch(3pm)
perl 5.38.2 - Generated Fri Dec 6 08:41:37 CST 2024