resulting derived work is distributed under the terms of a permission
notice identical to this one.
+\1f
+File: wget.info, Node: Time-Stamping, Next: Startup File, Prev: Following Links, Up: Top
+
+Time-Stamping
+*************
+
+ One of the most important aspects of mirroring information from the
+Internet is updating your archives.
+
+ Downloading the whole archive again and again, just to replace a few
+changed files is expensive, both in terms of wasted bandwidth and money,
+and the time to do the update. This is why all the mirroring tools
+offer the option of incremental updating.
+
+ Such an updating mechanism means that the remote server is scanned in
+search of "new" files. Only those new files will be downloaded in the
+place of the old ones.
+
+ A file is considered new if one of these two conditions are met:
+
+ 1. A file of that name does not already exist locally.
+
+ 2. A file of that name does exist, but the remote file was modified
+ more recently than the local file.
+
+ To implement this, the program needs to be aware of the time of last
+modification of both remote and local files. Such information are
+called the "time-stamps".
+
+ The time-stamping in GNU Wget is turned on using `--timestamping'
+(`-N') option, or through `timestamping = on' directive in `.wgetrc'.
+With this option, for each file it intends to download, Wget will check
+whether a local file of the same name exists. If it does, and the
+remote file is older, Wget will not download it.
+
+ If the local file does not exist, or the sizes of the files do not
+match, Wget will download the remote file no matter what the time-stamps
+say.
+
+* Menu:
+
+* Time-Stamping Usage::
+* HTTP Time-Stamping Internals::
+* FTP Time-Stamping Internals::
+
+\1f
+File: wget.info, Node: Time-Stamping Usage, Next: HTTP Time-Stamping Internals, Prev: Time-Stamping, Up: Time-Stamping
+
+Time-Stamping Usage
+===================
+
+ The usage of time-stamping is simple. Say you would like to
+download a file so that it keeps its date of modification.
+
+ wget -S http://www.gnu.ai.mit.edu/
+
+ A simple `ls -l' shows that the time stamp on the local file equals
+the state of the `Last-Modified' header, as returned by the server. As
+you can see, the time-stamping info is preserved locally, even without
+`-N'.
+
+ Several days later, you would like Wget to check if the remote file
+has changed, and download it if it has.
+
+ wget -N http://www.gnu.ai.mit.edu/
+
+ Wget will ask the server for the last-modified date. If the local
+file is newer, the remote file will not be re-fetched. However, if the
+remote file is more recent, Wget will proceed fetching it normally.
+
+ The same goes for FTP. For example:
+
+ wget ftp://ftp.ifi.uio.no/pub/emacs/gnus/*
+
+ `ls' will show that the timestamps are set according to the state on
+the remote server. Reissuing the command with `-N' will make Wget
+re-fetch *only* the files that have been modified.
+
+ In both HTTP and FTP retrieval Wget will time-stamp the local file
+correctly (with or without `-N') if it gets the stamps, i.e. gets the
+directory listing for FTP or the `Last-Modified' header for HTTP.
+
+ If you wished to mirror the GNU archive every week, you would use the
+following command every week:
+
+ wget --timestamping -r ftp://prep.ai.mit.edu/pub/gnu/
+
\1f
File: wget.info, Node: HTTP Time-Stamping Internals, Next: FTP Time-Stamping Internals, Prev: Time-Stamping Usage, Up: Time-Stamping
Enable/disable host-prefixed file names. `-nH' disables it.
continue = on/off
- Enable/disable continuation of the retrieval, the same as `-c'
+ Enable/disable continuation of the retrieval - the same as `-c'
(which enables it).
background = on/off
- Enable/disable going to background, the same as `-b' (which enables
- it).
+ Enable/disable going to background - the same as `-b' (which
+ enables it).
backup_converted = on/off
Enable/disable saving pre-converted files with the suffix `.orig'
- the same as `-K' (which enables it).
base = STRING
- Set base for relative URLs, the same as `-B'.
+ Consider relative URLs in URL input files forced to be interpreted
+ as HTML as being relative to STRING - the same as `-B'.
cache = on/off
When set to off, disallow server-caching. See the `-C' option.
Debug mode, same as `-d'.
delete_after = on/off
- Delete after download, the same as `--delete-after'.
+ Delete after download - the same as `--delete-after'.
dir_prefix = STRING
- Top of directory tree, the same as `-P'.
+ Top of directory tree - the same as `-P'.
dirstruct = on/off
- Turning dirstruct on or off, the same as `-x' or `-nd',
+ Turning dirstruct on or off - the same as `-x' or `-nd',
respectively.
domains = STRING
exclude_directories = STRING
Specify a comma-separated list of directories you wish to exclude
- from download, the same as `-X' (*Note Directory-Based Limits::).
+ from download - the same as `-X' (*Note Directory-Based Limits::).
exclude_domains = STRING
Same as `--exclude-domains' (*Note Domain Acceptance::).
follow_ftp = on/off
- Follow FTP links from HTML documents, the same as `-f'.
+ Follow FTP links from HTML documents - the same as `-f'.
follow_tags = STRING
Only follow certain HTML tags when doing a recursive retrieval,
force_html = on/off
If set to on, force the input filename to be regarded as an HTML
- document, the same as `-F'.
+ document - the same as `-F'.
ftp_proxy = STRING
Use STRING as FTP proxy, instead of the one specified in
environment.
glob = on/off
- Turn globbing on/off, the same as `-g'.
+ Turn globbing on/off - the same as `-g'.
header = STRING
Define an additional header, like `--header'.
include_directories = STRING
Specify a comma-separated list of directories you wish to follow
- when downloading, the same as `-I'.
+ when downloading - the same as `-I'.
input = STRING
Read the URLs from STRING, like `-i'.
the value in `Content-Length'.
logfile = STRING
- Set logfile, the same as `-o'.
+ Set logfile - the same as `-o'.
login = STRING
Your user name on the remote machine, for FTP. Defaults to
proxy loading, instead of the one specified in environment.
output_document = STRING
- Set the output filename, the same as `-O'.
+ Set the output filename - the same as `-O'.
+
+page_requisites = on/off
+ Download all ancillary documents necessary for a single HTML page
+ to display properly - the same as `-p'.
passive_ftp = on/off
- Set passive FTP, the same as `--passive-ftp'.
+ Set passive FTP - the same as `--passive-ftp'.
passwd = STRING
Set your FTP password to PASSWORD. Without this setting, the
Set proxy authentication password to STRING, like `--proxy-passwd'.
quiet = on/off
- Quiet mode, the same as `-q'.
+ Quiet mode - the same as `-q'.
quota = QUOTA
Specify the download quota, which is useful to put in the global
system settings.
reclevel = N
- Recursion level, the same as `-l'.
+ Recursion level - the same as `-l'.
recursive = on/off
- Recursive on/off, the same as `-r'.
+ Recursive on/off - the same as `-r'.
relative_only = on/off
- Follow only relative links, the same as `-L' (*Note Relative
+ Follow only relative links - the same as `-L' (*Note Relative
Links::).
remove_listing = on/off
what you are doing before changing the default (which is `on').
server_response = on/off
- Choose whether or not to print the HTTP and FTP server responses,
+ Choose whether or not to print the HTTP and FTP server responses -
the same as `-S'.
simple_host_check = on/off
Same as `-H'.
timeout = N
- Set timeout value, the same as `-T'.
+ Set timeout value - the same as `-T'.
timestamping = on/off
Turn timestamping on/off. The same as `-N' (*Note Time-Stamping::).
tries = N
- Set number of retries per URL, the same as `-t'.
+ Set number of retries per URL - the same as `-t'.
use_proxy = on/off
Turn proxy support on/off. The same as `-Y'.
verbose = on/off
- Turn verbose on/off, the same as `-v'/`-nv'.
+ Turn verbose on/off - the same as `-v'/`-nv'.
wait = N
- Wait N seconds between retrievals, the same as `-w'.
+ Wait N seconds between retrievals - the same as `-w'.
waitretry = N
Wait up to N seconds between retries of failed retrievals only -
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