NAME

       zsync - Partial/differential file download client over HTTP

SYNTAX

       zsync [ -u url ] [ -i inputfile ] [ -o outputfile ] [ { -s | -q } ] [ -k file.zsync ] [ -A
       hostname=username:password ] { filename | url }

       zsync -V

DESCRIPTION

       Downloads a file over HTTP. zsync uses a control file to determine whether any  blocks  in
       the file are already known to the downloader, and only downloads the new blocks.

       Either  a  filename  or  a  URL can be given on the command line - this is the path of the
       control file for the download, which normally has the name of the actual file to  downlaod
       with  .zsync  appended.  (To create this .zsync file you have to have a copy of the target
       file, so this file should be generated by the person providing the download).

       zsync downloads to your current directory. It looks for any file in the directory  of  the
       same  name as the file to download. If it finds one, it assumes that this is an earlier or
       incomplete version of the new file to download, and scans this file for any blocks that it
       can  use  to  build the target file. (It also looks for a file of the same name with .part
       appended, so it will automatically find previously interrupted zsync downloads  and  reuse
       the  data  already  downloaded.  If  you  know  that  the local file to use as input has a
       different name, you must use -i)

       zsync retrieves the rest of the target file over HTTP. Once the download is finished,  the
       old  version  (if the new file wants the same name) is moved aside (a .zs-old extension is
       appended). The modification time of the file is set to be the same as  the  remote  source
       file (if specified in the .zsync).

OPTIONS

       -A hostname=username:password
              Specifies  a  username  and  password to be used with the given hostname. -A can be
              used multiple times (with different hostnames), in cases where e.g. the
               .zsync file is on a different server from the  download,  or  there  are  multiple
              download servers (there could be different auth details for different servers - and
              zsync never assumes that your password should be sent to a server  other  than  the
              one named - otherwise redirects would be dangerous!).

       -i inputfile
              Specifies  (extra)  input  files. inputfile is scanned to identify blocks in common
              with the target file and zsync uses any blocks found. Can be used multiple times.

       -k file.zsync
              Indicates that zsync should save the zsync file that it downloads, with  the  given
              filename.  If  that file already exists, then zsync will make a conditional request
              to the web server, such that it will only download it again if the server's copy is
              newer.  zsync  will  append  .part  to  the  filename  for  storing  it while it is
              downloading, and will only overwrite the main file once the download is done -  and
              if the download is interrupted, it will resume using the data in the .part file.

       -o outputfile
              Override the default output file name.

       -q     Suppress the progress bar, download rate and ETA display.

       -s     Deprecated synonym for -q.

       -u url This  specifies  the  referring  URL.   If  you  have a .zsync file locally (if you
              downloaded it separately, with wget, say) and the .zsync file contains  a  relative
              URL,  you  need  to  specify where you got the .zsync file from so that zsync knows
              which server and path to use for the rest of the download  (this  is  analogous  to
              adding a <base href="..."> to a downloaded web page to make the links work).

       -V     Prints the version of zsync.

FILES

ENVIRONMENT VARIABLES

       http_proxy
              Should  be  the  [http://]hostname:port  for  your web proxy, if one is required to
              access the target web server(s).

EXAMPLES

       zsync -i  /var/lib/apt/lists/server.debian.org_debian_dists_etch_main_binary-i386_Packages
       http://zsync.moria.org.uk/s/etch/Packages.zsync

AUTHORS

       Colin Phipps <cph@moria.org.uk>

SEE ALSO

       zsyncmake(1)