使用wget工具抓取网页和图片

发表于1年前(2014-12-17 11:29) 阅读（2471） | 评论（14） 85人收藏此文章, 我要收藏

目录[-]

奇怪的需求

公司需要将服务器的网页缓存到路由器，用户在访问该网页时就直接取路由器上的缓存即可。虽然我不知道这个需求有什么意义，但还是尽力去实现吧。

wget概述

wget是unix和类unix下的一个网页抓取工具，待我熟悉它后，发现它的功能远不止这些。但是这篇博文只说怎么抓取一个指定URL以及它下面的相关内容（包括html,js,css,图片）并将内容里的绝对路径换成相对路径。网上搜到一堆有关wget的文章，关于它怎么抓取网页和相关的图片资源，反正我是没有找到一篇实用的，都以失败告终。

这是wget -h > ./help_wget.txt 后的文件内容

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GNU Wget 1.16, a non-interactive network retriever.

Usage: wget [OPTION]... [URL]...

Mandatory arguments to long options are mandatory for short options too.

Startup:

-V, --version display the version of Wget and exit.

-h, --help print this help.

-b, --background go to background after startup.

-e, --execute=COMMAND execute a `.wgetrc'-style command.

Logging and input file:

-o, --output-file=FILE log messages to FILE.

-a, --append-output=FILE append messages to FILE.

-q, --quiet quiet (no output).

-v, --verbose be verbose (this is the default).

-nv, --no-verbose turn off verboseness, without being quiet.

--report-speed=TYPE Output bandwidth as TYPE. TYPE can be bits.

-i, --input-file=FILE download URLs found in local or external FILE.

-F, --force-html treat input file as HTML.

-B, --base=URL resolves HTML input-file links (-i -F)

relative to URL.

--config=FILE Specify config file to use.

--no-config Do not read any config file.

Download:

-t, --tries=NUMBER set number of retries to NUMBER (0 unlimits).

--retry-connrefused retry even if connection is refused.

-O, --output-document=FILE write documents to FILE.

-nc, --no-clobber skip downloads that would download to

existing files (overwriting them).

-c, --continue resume getting a partially-downloaded file.

--start-pos=OFFSET start downloading from zero-based position OFFSET.

--progress=TYPE select progress gauge type.

--show-progress display the progress bar in any verbosity mode.

-N, --timestamping don't re-retrieve files unless newer than

local.

--no-use-server-timestamps don't set the local file's timestamp by

the one on the server.

-S, --server-response print server response.

--spider don't download anything.

-T, --timeout=SECONDS set all timeout values to SECONDS.

--dns-timeout=SECS set the DNS lookup timeout to SECS.

--connect-timeout=SECS set the connect timeout to SECS.

--read-timeout=SECS set the read timeout to SECS.

-w, --wait=SECONDS wait SECONDS between retrievals.

--waitretry=SECONDS wait 1..SECONDS between retries of a retrieval.

--random-wait wait from 0.5*WAIT...1.5*WAIT secs between retrievals.

--no-proxy explicitly turn off proxy.

-Q, --quota=NUMBER set retrieval quota to NUMBER.

--bind-address=ADDRESS bind to ADDRESS (hostname or IP) on local host.

--limit-rate=RATE limit download rate to RATE.

--no-dns-cache disable caching DNS lookups.

--restrict-file-names=OS restrict chars in file names to ones OS allows.

--ignore-case ignore case when matching files/directories.

-4, --inet4-only connect only to IPv4 addresses.

-6, --inet6-only connect only to IPv6 addresses.

--prefer-family=FAMILY connect first to addresses of specified family,

one of IPv6, IPv4, or none.

--user=USER set both ftp and http user to USER.

--password=PASS set both ftp and http password to PASS.

--ask-password prompt for passwords.

--no-iri turn off IRI support.

--local-encoding=ENC use ENC as the local encoding for IRIs.

--remote-encoding=ENC use ENC as the default remote encoding.

--unlink remove file before clobber.

Directories:

-nd, --no-directories don't create directories.

-x, --force-directories force creation of directories.

-nH, --no-host-directories don't create host directories.

--protocol-directories use protocol name in directories.

-P, --directory-prefix=PREFIX save files to PREFIX/...

--cut-dirs=NUMBER ignore NUMBER remote directory components.

HTTP options:

--http-user=USER set http user to USER.

--http-password=PASS set http password to PASS.

--no-cache disallow server-cached data.

--default-page=NAME Change the default page name (normally

this is `index.html'.).

-E, --adjust-extension save HTML/CSS documents with proper extensions.

--ignore-length ignore `Content-Length' header field.

--header=STRING insert STRING among the headers.

--max-redirect maximum redirections allowed per page.

--proxy-user=USER set USER as proxy username.

--proxy-password=PASS set PASS as proxy password.

--referer=URL include `Referer: URL' header in HTTP request.

--save-headers save the HTTP headers to file.

-U, --user-agent=AGENT identify as AGENT instead of Wget/VERSION.

--no-http-keep-alive disable HTTP keep-alive (persistent connections).

--no-cookies don't use cookies.

--load-cookies=FILE load cookies from FILE before session.

--save-cookies=FILE save cookies to FILE after session.

--keep-session-cookies load and save session (non-permanent) cookies.

--post-data=STRING use the POST method; send STRING as the data.

--post-file=FILE use the POST method; send contents of FILE.

--method=HTTPMethod use method "HTTPMethod" in the request.

--body-data=STRING Send STRING as data. --method MUST be set.

--body-file=FILE Send contents of FILE. --method MUST be set.

--content-disposition honor the Content-Disposition header when

choosing local file names (EXPERIMENTAL).

--content-on-error output the received content on server errors.

--auth-no-challenge send Basic HTTP authentication information

without first waiting for the server's

challenge.

HTTPS (SSL/TLS) options:

--secure-protocol=PR choose secure protocol, one of auto, SSLv2,

SSLv3, TLSv1 and PFS.

--https-only only follow secure HTTPS links

--no-check-certificate don't validate the server's certificate.

--certificate=FILE client certificate file.

--certificate-type=TYPE client certificate type, PEM or DER.

--private-key=FILE private key file.

--private-key-type=TYPE private key type, PEM or DER.

--ca-certificate=FILE file with the bundle of CA's.

--ca-directory=DIR directory where hash list of CA's is stored.

--random-file=FILE file with random data for seeding the SSL PRNG.

--egd-file=FILE file naming the EGD socket with random data.

FTP options:

--ftp-user=USER set ftp user to USER.

--ftp-password=PASS set ftp password to PASS.

--no-remove-listing don't remove `.listing' files.

--no-glob turn off FTP file name globbing.

--no-passive-ftp disable the "passive" transfer mode.

--preserve-permissions preserve remote file permissions.

--retr-symlinks when recursing, get linked-to files (not dir).

WARC options:

--warc-file=FILENAME save request/response data to a .warc.gz file.

--warc-header=STRING insert STRING into the warcinfo record.

--warc-max-size=NUMBER set maximum size of WARC files to NUMBER.

--warc-cdx write CDX index files.

--warc-dedup=FILENAME do not store records listed in this CDX file.

--no-warc-compression do not compress WARC files with GZIP.

--no-warc-digests do not calculate SHA1 digests.

--no-warc-keep-log do not store the log file in a WARC record.

--warc-tempdir=DIRECTORY location for temporary files created by the

WARC writer.

Recursive download:

-r, --recursive specify recursive download.

-l, --level=NUMBER maximum recursion depth (inf or 0 for infinite).

--delete-after delete files locally after downloading them.

-k, --convert-links make links in downloaded HTML or CSS point to

local files.

--backups=N before writing file X, rotate up to N backup files.

-K, --backup-converted before converting file X, back up as X.orig.

-m, --mirror shortcut for -N -r -l inf --no-remove-listing.

-p, --page-requisites get all images, etc. needed to display HTML page.

--strict-comments turn on strict (SGML) handling of HTML comments.

Recursive accept/reject:

-A, --accept=LIST comma-separated list of accepted extensions.

-R, --reject=LIST comma-separated list of rejected extensions.

--accept-regex=REGEX regex matching accepted URLs.

--reject-regex=REGEX regex matching rejected URLs.

--regex-type=TYPE regex type (posix).

-D, --domains=LIST comma-separated list of accepted domains.

--exclude-domains=LIST comma-separated list of rejected domains.

--follow-ftp follow FTP links from HTML documents.

--follow-tags=LIST comma-separated list of followed HTML tags.

--ignore-tags=LIST comma-separated list of ignored HTML tags.

-H, --span-hosts go to foreign hosts when recursive.

-L, --relative follow relative links only.

-I, --include-directories=LIST list of allowed directories.

--trust-server-names use the name specified by the redirection

url last component.

-X, --exclude-directories=LIST list of excluded directories.

-np, --no-parent don't ascend to the parent directory.

Mail bug reports and suggestions to <bug-wget@gnu.org>.

wget尝试

根据wget的帮助文档，我尝试了下面这条命令

1	`wget -r -np -pk -nH -P ./download` `http://www.baidu.com`

解释一下这些参数

-r 递归下载所有内容

-np 只下载给定URL下的内容，不下载它的上级内容

-p 下载有关页面需要用到的所有资源，包括图片和css样式

-k 将绝对路径转换为相对路径（这个很重要，为了在用户打开网页的时候，加载的相关资源都在本地寻找）

-nH 禁止wget以接收的URL为名称创建文件夹（如果没有这个，这条命令会将下载的内容存在./download/www.baidu.com/下）

-P 下载到哪个路径，这里是当前文件夹下的download文件夹下，没有的话，wget会帮你自动创建

这些选项都符合目前的这个需求，单结果很意外，并不是我们想象的那么简单，wget并没有给我们想要的东西

你如果执行了这条命令，会发现在当前的download文件夹中只是下载了一个index.html和一个robots.txt，而index.html文件所需要的图片也并没有被下载

<img>标签中的路径也没有被替换成相对路径，可能只是去掉了"http:"这个字符串而已。

至于为什么会这样，请继续往下看。

wget正解

因为上面的命令行不通，所以，脑洞全开。来吧，让我们写一个shell脚本，名称为wget_cc内容如下

#!/bin/sh

URL="$2"

PATH="$1"

echo "download url: $URL"

echo "download dir: $PATH"

/usr/bin/wget -e robots=off -w 1 -xq -np -nH -pk -m -t 1 -P "$PATH" "$URL"

echo "success to download"

需要注意的是，我的wget是在/usr/bin目录下（这里必须写全路径），你可以使用which wget这个命令确定你的wget路径所在，然后替换到脚本中就行了。

这里多加了几个参数，解释一下：

-e 用法是‘-e command’

用来执行额外的.wgetrc命令。就像vim的配置存在.vimrc文件中一样，wget也用.wgetrc文件来存放它的配置。也就是说在wget执行之前，会先执行.wgetrc文件中的配置命令。一个典型的.wgetrc文件可以参考：

http://www.gnu.org/software/wget/manual/html_node/Sample-Wgetrc.html

http://www.gnu.org/software/wget/manual/html_node/Wgetrc-Commands.html

用户可以在不改写.wgetrc文件的情况下，用-e选项指定额外的配置命令。如果想要制定多个配置命令，-e command1 -e command2 ... -e commandN即可。这些制定的配置命令，会在.wgetrc中所有命令之后执行，因此会覆盖.wgetrc中相同的配置项。

这里robots=off是因为wget默认会根据网站的robots.txt进行操作，如果robots.txt里是User-agent: * Disallow: /的话，wget是做不了镜像或者下载目录的。

这就是前面为什么下载不了图片和其他资源的原因所在了，因为你要爬的HOST禁止蜘蛛去爬它，而wget使用 -e robots=off 这个选项可以通过这个命令绕过这个限制。

-x 创建镜像网站对应的目录结构

-q 静默下载，即不显示下载信息，你如果想知道wget当前在下载什么资源的话，可以去掉这个选项

-m 它会打开镜像相关的选项，比如无限深度的子目录递归下载。

-t times 某个资源下载失败后的重试下载次数

-w seconds 资源请求下载之间的等待时间（减轻服务器的压力）

剩下有不懂的你就去挖文档吧。

写好后保存退出，执行：

1	`chmod` `744 wget_cc`

OK，这样脚本就能直接执行，而不用在每条命令前带 /bin/sh 让sh去解释它了。

下面就让脚本执行起来吧！

1	`./wget_cc` `./download` `http://www.baidu.com`

下载完成后的目录结构

OK，然后再查看<img>标签中的src属性，

src="img/bd_logo1.png"

果然换成了相对路径啊，大功告成，觉得对您有帮助的请点个赞吧！