moparisthebest/wget
1
0
Fork 0
mirror of https://github.com/moparisthebest/wget synced 2024-07-03 16:38:41 -04:00
Code Issues Releases Wiki Activity

[svn] wget.texi: Corrections, clarifications, and English fixes to time-stamping

Browse Source 
documentation and a couple other places.
This commit is contained in:
dan 2001-02-23 12:16:07 -08:00
parent 776d65e829
commit a09ac9ea6c
2 changed files with 36 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
doc/ChangeLog
View File

@ -1,3 +1,8 @@
2001-02-23 Dan Harkless <wget@harkless.org>
* wget.texi: Corrections, clarifications, and English fixes to
time-stamping documentation and a couple other places.
2001-02-22 Dan Harkless <wget@harkless.org>
* Makefile.in: Make wget man page and install it if we have

52
doc/wget.texi
View File

@ -581,7 +581,7 @@ Unfortunately this also happens if the local file is the same length as
the server file---this will be fixed in a future version of Wget, but in
the meantime you can use @samp{--timestamping} to prevent this on files
for which the server gives timestamps (e.g. static files but not CGI
output or directory listings).
output or @sc{http} directory listings).
On the other side of the coin, while using @samp{-c}, any file that's
bigger on the server than locally will be considered an incomplete
@ -1576,8 +1576,8 @@ recently than the local file.
@end enumerate
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 @dfn{time-stamps}.
modification of both local and remote files. We call this information the
@dfn{time-stamp} of a file.
The time-stamping in GNU Wget is turned on using @samp{--timestamping}
(@samp{-N}) option, or through @code{timestamping = on} directive in
@ -1610,7 +1610,7 @@ wget -S http://www.gnu.ai.mit.edu/
A simple @code{ls -l} shows that the time stamp on the local file equals
the state of the @code{Last-Modified} header, as returned by the server.
As you can see, the time-stamping info is preserved locally, even
without @samp{-N}.
without @samp{-N} (at least for @sc{http}).
Several days later, you would like Wget to check if the remote file has
changed, and download it if it has.
@ -1620,31 +1620,37 @@ wget -N http://www.gnu.ai.mit.edu/
@end example
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.
has the same timestamp as the server, or a newer one, the remote file
will not be re-fetched. However, if the remote file is more recent,
Wget will proceed to fetch it.
The same goes for @sc{ftp}. For example:
@example
wget ftp://ftp.ifi.uio.no/pub/emacs/gnus/*
wget "ftp://ftp.ifi.uio.no/pub/emacs/gnus/*"
@end example
@code{ls} will show that the timestamps are set according to the state
on the remote server. Reissuing the command with @samp{-N} will make
Wget re-fetch @emph{only} the files that have been modified.
(The quotes around that URL are to prevent the shell from trying to
interpret the @samp{*}.)
In both @sc{http} and @sc{ftp} retrieval Wget will time-stamp the local
file correctly (with or without @samp{-N}) if it gets the stamps,
i.e. gets the directory listing for @sc{ftp} or the @code{Last-Modified}
header for @sc{http}.
After download, a local directory listing will show that the timestamps
match those on the remote server. Reissuing the command with @samp{-N}
will make Wget re-fetch @emph{only} the files that have been modified
since the last download.
If you wished to mirror the GNU archive every week, you would use the
following command every week:
If you wished to mirror the GNU archive every week, you would use a
command like the following, weekly:
@example
wget --timestamping -r ftp://prep.ai.mit.edu/pub/gnu/
wget --timestamping -r ftp://ftp.gnu.org/pub/gnu/
@end example
Note that time-stamping will only work for files for which the server
gives a timestamp. For @sc{http}, this depends on getting a
@code{Last-Modified} header. For @sc{ftp}, this depends on getting a
directory listing with dates in a format that Wget can parse
(@pxref{FTP Time-Stamping Internals}).
@node HTTP Time-Stamping Internals, FTP Time-Stamping Internals, Time-Stamping Usage, Time-Stamping
@section HTTP Time-Stamping Internals
@cindex http time-stamping
@ -1685,10 +1691,14 @@ In theory, @sc{ftp} time-stamping works much the same as @sc{http}, only
@sc{ftp} has no headers---time-stamps must be received from the
directory listings.
For each directory files must be retrieved from, Wget will use the
@code{LIST} command to get the listing. It will try to analyze the
listing, assuming that it is a Unix @code{ls -l} listing, and extract
the time-stamps. The rest is exactly the same as for @sc{http}.
If an @sc{ftp} download is recursive or uses globbing, Wget will use the
@sc{ftp} @code{LIST} command to get a file listing for the directory
containing the desired file(s). It will try to analyze the listing,
treating it like Unix @code{ls -l} output, extracting the time-stamps.
The rest is exactly the same as for @sc{http}. Note that when
retrieving individual files from an @sc{ftp} server without using
globbing or recursion, listing files will not be downloaded (and thus
files will not be time-stamped) unless @samp{-N} is specified.
Assumption that every directory listing is a Unix-style listing may
sound extremely constraining, but in practice it is not, as many