Note that a combination with -k is only well-defined for downloading a single document.
When running Wget without -N, -nc, or -r,
downloading the same file in the same directory will result in the
original copy of file being preserved and the second copy being
named file.1. If that file is downloaded yet again, the
third copy will be named file.2, and so on. When
-nc is specified, this behavior is suppressed, and Wget will
refuse to download newer copies of file. Therefore,
“no-clobber” is actually a misnomer in this mode—it's not
clobbering that's prevented (as the numeric suffixes were already
preventing clobbering), but rather the multiple version saving that's
prevented.
When running Wget with -r, but without -N or -nc, re-downloading a file will result in the new copy simply overwriting the old. Adding -nc will prevent this behavior, instead causing the original version to be preserved and any newer copies on the server to be ignored.
When running Wget with -N, with or without -r, the decision as to whether or not to download a newer copy of a file depends on the local and remote timestamp and size of the file (see Time-Stamping). -nc may not be specified at the same time as -N.
Note that when -nc is specified, files with the suffixes .html or .htm will be loaded from the local disk and parsed as if they had been retrieved from the Web.
wget -c ftp://sunsite.doc.ic.ac.uk/ls-lR.Z
If there is a file named ls-lR.Z in the current directory, Wget will assume that it is the first portion of the remote file, and will ask the server to continue the retrieval from an offset equal to the length of the local file.
Note that you don't need to specify this option if you just want the current invocation of Wget to retry downloading a file should the connection be lost midway through. This is the default behavior. -c only affects resumption of downloads started prior to this invocation of Wget, and whose local files are still sitting around.
Without -c, the previous example would just download the remote file to ls-lR.Z.1, leaving the truncated ls-lR.Z file alone.
Beginning with Wget 1.7, if you use -c on a non-empty file, and it turns out that the server does not support continued downloading, Wget will refuse to start the download from scratch, which would effectively ruin existing contents. If you really want the download to start from scratch, remove the file.
Also beginning with Wget 1.7, if you use -c on a file which is of equal size as the one on the server, Wget will refuse to download the file and print an explanatory message. The same happens when the file is smaller on the server than locally (presumably because it was changed on the server since your last download attempt)—because “continuing” is not meaningful, no download occurs.
On the other side of the coin, while using -c, any file that's
bigger on the server than locally will be considered an incomplete
download and only (length(remote) - length(local)) bytes will be
downloaded and tacked onto the end of the local file. This behavior can
be desirable in certain cases—for instance, you can use wget -c
to download just the new portion that's been appended to a data
collection or log file.
However, if the file is bigger on the server because it's been changed, as opposed to just appended to, you'll end up with a garbled file. Wget has no way of verifying that the local file is really a valid prefix of the remote file. You need to be especially careful of this when using -c in conjunction with -r, since every file will be considered as an "incomplete download" candidate.
Another instance where you'll get a garbled file if you try to use -c is if you have a lame http proxy that inserts a “transfer interrupted” string into the local file. In the future a “rollback” option may be added to deal with this case.
Note that -c only works with ftp servers and with http
servers that support the Range header.
The “bar” indicator is used by default. It draws an ascii progress bar graphics (a.k.a “thermometer” display) indicating the status of retrieval. If the output is not a TTY, the “dot” bar will be used by default.
Use --progress=dot to switch to the “dot” display. It traces the retrieval by printing dots on the screen, each dot representing a fixed amount of downloaded data.
When using the dotted retrieval, you may also set the style by
specifying the type as dot:style. Different styles assign
different meaning to one dot. With the default style each dot
represents 1K, there are ten dots in a cluster and 50 dots in a line.
The binary style has a more “computer”-like orientation—8K
dots, 16-dots clusters and 48 dots per line (which makes for 384K
lines). The mega style is suitable for downloading very large
files—each dot represents 64K retrieved, there are eight dots in a
cluster, and 48 dots on each line (so each line contains 3M).
Note that you can set the default style using the progress
command in .wgetrc. That setting may be overridden from the
command line. The exception is that, when the output is not a TTY, the
“dot” progress will be favored over “bar”. To force the bar output,
use --progress=bar:force.
wget --spider --force-html -i bookmarks.html
This feature needs much more work for Wget to get close to the functionality of real web spiders.
When interacting with the network, Wget can check for timeout and abort the operation if it takes too long. This prevents anomalies like hanging reads and infinite connects. The only timeout enabled by default is a 900-second read timeout. Setting a timeout to 0 disables it altogether. Unless you know what you are doing, it is best not to change the default timeout settings.
All timeout-related options accept decimal values, as well as subsecond values. For example, 0.1 seconds is a legal (though unwise) choice of timeout. Subsecond timeouts are useful for checking server response times or for testing network latency.
Of course, the remote server may choose to terminate the connection sooner than this option requires. The default read timeout is 900 seconds.
This option allows the use of decimal numbers, usually in conjunction with power suffixes; for example, --limit-rate=2.5k is a legal value.
Note that Wget implements the limiting by sleeping the appropriate amount of time after a network read that took less time than specified by the rate. Eventually this strategy causes the TCP transfer to slow down to approximately the specified rate. However, it may take some time for this balance to be achieved, so don't be surprised if limiting the rate doesn't work well with very small files.
m suffix, in hours using h
suffix, or in days using d suffix.
Specifying a large value for this option is useful if the network or the destination host is down, so that Wget can wait long enough to reasonably expect the network error to be fixed before the retry.
Note that this option is turned on by default in the global wgetrc file.
A recent article in a publication devoted to development on a popular consumer platform provided code to perform this analysis on the fly. Its author suggested blocking at the class C address level to ensure automated retrieval programs were blocked despite changing DHCP-supplied addresses.
The --random-wait option was inspired by this ill-advised recommendation to block many unrelated users from a web site due to the actions of one.
*_proxy environment
variable is defined.
For more information about the use of proxies with Wget, See Proxies.
Note that quota will never affect downloading a single file. So if you specify wget -Q10k ftp://wuarchive.wustl.edu/ls-lR.gz, all of the ls-lR.gz will be downloaded. The same goes even when several urls are specified on the command-line. However, quota is respected when retrieving either recursively, or from an input file. Thus you may safely type wget -Q2m -i sites—download will be aborted when the quota is exceeded.
Setting quota to 0 or to inf unlimits the download quota.
However, it has been reported that in some situations it is not
desirable to cache host names, even for the duration of a
short-running application like Wget. With this option Wget issues a
new DNS lookup (more precisely, a new call to gethostbyname or
getaddrinfo) each time it makes a new connection. Please note
that this option will not affect caching that might be
performed by the resolving library or by an external caching layer,
such as NSCD.
If you don't understand exactly what this option does, you probably won't need it.
By default, Wget escapes the characters that are not valid as part of file names on your operating system, as well as control characters that are typically unprintable. This option is useful for changing these defaults, either because you are downloading to a non-native partition, or because you want to disable escaping of the control characters.
When mode is set to “unix”, Wget escapes the character / and the control characters in the ranges 0–31 and 128–159. This is the default on Unix-like OS'es.
When mode is set to “windows”, Wget escapes the characters \, |, /, :, ?, ", *, <, >, and the control characters in the ranges 0–31 and 128–159. In addition to this, Wget in Windows mode uses + instead of : to separate host and port in local file names, and uses @ instead of ? to separate the query portion of the file name from the rest. Therefore, a URL that would be saved as www.xemacs.org:4300/search.pl?input=blah in Unix mode would be saved as www.xemacs.org+4300/search.pl@input=blah in Windows mode. This mode is the default on Windows.
If you append ,nocontrol to the mode, as in unix,nocontrol, escaping of the control characters is also switched off. You can use --restrict-file-names=nocontrol to turn off escaping of control characters without affecting the choice of the OS to use as file name restriction mode.
Neither options should be needed normally. By default, an IPv6-aware Wget will use the address family specified by the host's DNS record. If the DNS specifies both an A record and an AAAA record, Wget will try them in sequence until it finds one it can connect to.
These options can be used to deliberately force the use of IPv4 or
IPv6 address families on dual family systems, usually to aid debugging
or to deal with broken network configuration. Only one of
--inet6-only and --inet4-only may be specified in the
same command. Neither option is available in Wget compiled without
IPv6 support.
This avoids spurious errors and connect attempts when accessing hosts
that resolve to both IPv6 and IPv4 addresses from IPv4 networks. For
example, www.kame.net resolves to
2001:200:0:8002:203:47ff:fea5:3085 and to
203.178.141.194. When the preferred family is IPv4, the
IPv4 address is used first; when the preferred family is IPv6,
the IPv6 address is used first; if the specified value is none,
the address order returned by DNS is used without change.
Unlike -4 and -6, this option doesn't inhibit access to
any address family, it only changes the order in which the
addresses are accessed. Also note that the reordering performed by
this option is stable—it doesn't affect order of addresses of
the same family. That is, the relative order of all IPv4 addresses
and of all IPv6 addresses remains intact in all cases.