Manpages - File_Fetch.3perl
Table of Contents
NAME
:Fetch - A generic file fetching mechanism
SYNOPSIS
use :Fetch; ### build a :Fetch object ### my $ff = :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
: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 beindex.htmlrather thanindex.html?x=y.
METHODS
$ff = :Fetch->new( uri => ’http://some.where.com/dir/file.txt’
); Parses the uri and creates a corresponding 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
: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, :Tiny, wget, curl, lftp, fetch, :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 :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 :Lite => httplite :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 :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:
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.