Net::FTP::RetrHandle - Tied or IO::Handle-compatible interface to a file retrieved by FTP
Provides a file reading interface for reading all or parts of files located on a remote FTP server, including emulation of seek and support for downloading only the parts of the file requested.
seek
Support for skipping the beginning of the file is implemented with the FTP REST command, which starts a retrieval at any point in the file. Support for skipping the end of the file is implemented with the FTP ABOR command, which stops the transfer. With these two commands and some careful tracking of the current file position, we're able to reliably emulate a seek/read pair, and get only the parts of the file that are actually read.
REST
ABOR
seek/read
This was originally designed for use with Archive::Zip; it's reliable enough that the table of contents and individual files can be extracted from a remote ZIP archive without downloading the whole thing. See EXAMPLES below.
An interface compatible with IO::Handle is provided, along with a tie-based interface.
tie
Remember that an FTP server can only do one thing at a time, so make sure to close your connection before asking the FTP server to do nything else.
close
Creates a new IO::Handle-compatible object to fetch all or parts of $filename using the FTP connection $ftp.
$filename
$ftp
Available options:
If we need to move forward in a file or close the connection, sometimes it's faster to just read the bytes we don't need than to abort the connection and restart. This setting tells how many unnecessary bytes we're willing to read rather than abort. An appropriate setting depends on the speed of transferring files and the speed of reconnecting to the server.
When doing buffered reads, how many bytes to read at once. The default is the same as the default for Net::FTP, so it's generally best to leave it alone.
If set to a true value, we assume the server is already in binary mode, and don't try to set it.
Most of the methods implemented behave exactly like those from IO::Handle.
These methods are implemented: binmode, clearerr, close, eof, error, getc, getline, getlines, getpos, read, seek, setpos, sysseek, tell, ungetc, opened.
binmode
clearerr
eof
error
getc
getline
getlines
getpos
read
setpos
sysseek
tell
ungetc
opened
Instead of a IO::Handle-compatible interface, you can use a tie-based interface to use the standard Perl I/O operators. You can use it like this:
use Net::FTP::RetrHandle; # Create FTP object in $ftp # Store filename in $filename tie *FH, 'Net::FTP::RetrHandle', $ftp, $filename or die "Error in tie!\n";
Here's an example of listing a Zip file without downloading the whole thing:
#!/usr/bin/perl use warnings; use strict; use Net::FTP; use Net::FTP::AutoReconnect; use Net::FTP::RetrHandle; use Archive::Zip; my $ftp = Net::FTP::AutoReconnect->new("ftp.info-zip.com", Debug => $ENV{DEBUG}) or die "connect error\n"; $ftp->login('anonymous','example@example.com') or die "login error\n"; $ftp->cwd('/pub/infozip/UNIX/LINUX') or die "cwd error\n"; my $fh = Net::FTP::RetrHandle->new($ftp,'unz551x-glibc.zip') or die "Couldn't get handle to remote file\n"; my $zip = Archive::Zip->new($fh) or die "Couldn't create Zip object\n"; foreach my $fn ($zip->memberNames()) { print "unz551-glibc.zip: $fn\n"; }
Scott Gifford <sgifford@suspectclass.com>
The distinction between tied filehandles and IO::Handle-compatible filehandles should be blurrier. It seems like other file handle objects you can freely mix method calls and traditional Perl operations, but I can't figure out how to do it.
IO::Handle
Many FTP servers don't like frequent connection aborts. If that's the case, try Net::FTP::AutoReconnect, which will hide much of that from you.
If the filehandle is tied and created with gensym, readline doesn't work with older versions of Perl. No idea why.
gensym
readline
Net::FTP, Net::FTP::AutoReconnect, IO::Handle.
Copyright (c) 2006 Scott Gifford. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Net::FTP::RetrHandle, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Net::FTP::RetrHandle
CPAN shell
perl -MCPAN -e shell install Net::FTP::RetrHandle
For more information on module installation, please visit the detailed CPAN module installation guide.