Wednesday, May 7, 2008

All about Wget

Name

Wget - The non-interactive network downloader.



Synopsis

wget [option]... [ URL ]...



Description

Wget is a free utility for non-interactive download of files from the Web. It supports HTTP , HTTPS , and FTP protocols, as well as retrieval through HTTP proxies.

Wget is non-interactive, meaning that it can work in the background, while the user is not logged on. This allows you to start a retrieval and disconnect from the system, letting Wget finish the work. By contrast, most of the Web browsers require constant user's presence, which can be a great hindrance when transferring a lot of data.

Wget can follow links in HTML and XHTML pages and create local versions of remote web sites, fully recreating the directory structure of the original site. This is sometimes referred to as ''recursive downloading.'' While doing that, Wget respects the Robot Exclusion Standard (/robots.txt). Wget can be instructed to convert the links in downloaded HTML files to the local files for offline viewing.

Wget has been designed for robustness over slow or unstable network connections; if a download fails due to a network problem, it will keep retrying until the whole file has been retrieved. If the server supports regetting, it will instruct the server to continue the download from where it left off.



Options

Since Wget uses GNU getopt to process command-line arguments, every option has a long form along with the short one. Long options are more convenient to remember, but take time to type. You may freely mix different option styles, or specify options after the command-line arguments. Thus you may write:



wget -r --tries=10 http://fly.srk.fer.hr/ -o log

The space between the option accepting an argument and the argument may be omitted. Instead -o log you can write -olog.

You may put several options that do not require arguments together, like:



wget -drc

This is a complete equivalent of:

wget -d -r -c

Since the options can be specified after the arguments, you may terminate them with --. So the following will try to download URL -x, reporting failure to log:

wget -o log -- -x

The options that accept comma-separated lists all respect the convention that specifying an empty list clears its value. This can be useful to clear the .wgetrc settings. For instance, if your .wgetrc sets "exclude_directories" to /cgi-bin, the following example will first reset it, and then set it to exclude /~nobody and /~somebody. You can also clear the lists in .wgetrc.

wget -X '' -X /~nobody,/~somebody

Most options that do not accept arguments are boolean options, so named because their state can be captured with a yes-or-no (''boolean'') variable. For example, --follow-ftp tells Wget to follow FTP links from HTML files and, on the other hand, --no-glob tells it not to perform file globbing on FTP URLs. A boolean option is either affirmative or negative (beginning with --no). All such options share several properties.

Unless stated otherwise, it is assumed that the default behavior is the opposite of what the option accomplishes. For example, the documented existence of --follow-ftp assumes that the default is to not follow FTP links from HTML pages.

Affirmative options can be negated by prepending the --no- to the option name; negative options can be negated by omitting the --no- prefix. This might seem superfluous---if the default for an affirmative option is to not do something, then why provide a way to explicitly turn it off? But the startup file may in fact change the default. For instance, using "follow_ftp = off" in .wgetrc makes Wget not follow FTP links by default, and using --no-follow-ftp is the only way to restore the factory default from the command line.



Basic Startup Options

-V, --version

Display the version of Wget.



-h, --help

Print a help message describing all of Wget's command-line options.



-b, --background

Go to background immediately after startup. If no output file is specified via the -o, output is redirected to wget-log.



-e command, --execute command Execute command as if it were a part of .wgetrc. A command thus invoked will be executed after the commands in .wgetrc, thus taking precedence over them. If you need to specify more than one wgetrc command, use multiple instances of -e.

Logging and Input File Options



-o logfile , --output-file=logfile

Log all messages to logfile. The messages are normally reported to standard error.



-a logfile , --append-output=logfile

Append to logfile. This is the same as -o, only it appends to logfile instead of overwriting the old log file. If logfile does not exist, a new file is created.



-d , --debug

Turn on debug output, meaning various information important to the developers of Wget if it does not work properly. Your system administrator may have chosen to compile Wget without debug support, in which case -d will not work. Please note that compiling with debug support is always safe---Wget compiled with the debug support will not print any debug info unless requested with -d.



-q , --quiet

Turn off Wget's output.



-v , --verbose

Turn on verbose output, with all the available data. The default output is verbose.



-nv , --no-verbose

Turn off verbose without being completely quiet (use -q for that), which means that error messages and basic information still get printed.



-i file , --input-file=file

Read URLs from file. If - is specified as file, URLs are read from the standard input. (Use ./- to read from a file literally named -.)

If this function is used, no URLs need be present on the command line. If there are URLs both on the command line and in an input file, those on the command lines will be the first ones to be retrieved. The file need not be an HTML document (but no harm if it is)---it is enough if the URLs are just listed sequentially.

However, if you specify --force-html, the document will be regarded as html. In that case you may have problems with relative links, which you can solve either by adding "" to the documents or by specifying --base=url on the command line.



-F , --force-html

When input is read from a file, force it to be treated as an HTML file. This enables you to retrieve relative links from existing HTML files on your local disk, by adding "" to HTML , or using the --base command-line option.



-B URL , --base= URL

Prepends URL to relative links read from the file specified with the -i option.



Download Options



--bind-address= ADDRESS

When making client TCP/IP connections, bind to ADDRESS on the local machine. ADDRESS may be specified as a hostname or IP address. This option can be useful if your machine is bound to multiple IPs.



-t number , --tries=number

Set number of retries to number. Specify 0 or inf for infinite retrying. The default is to retry 20 times, with the exception of fatal errors like ''connection refused'' or ''not found'' (404), which are not retried.



-O file , --output-document=file

The documents will not be written to the appropriate files, but all will be concatenated together and written to file. If - is used as file, documents will be printed to standard output, disabling link conversion. (Use ./- to print to a file literally named -.)

Note that a combination with -k is only well-defined for downloading a single document.



-nc , --no-clobber

If a file is downloaded more than once in the same directory, Wget's behavior depends on a few options, including -nc. In certain cases, the local file will be clobbered, or overwritten, upon repeated download. In other cases it will be preserved.

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. -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.



-c , --continue

Continue getting a partially-downloaded file. This is useful when you want to finish up a download started by a previous instance of Wget, or by another program. For instance:

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.



--progress=type

Select the type of the progress indicator you wish to use. Legal indicators are ''dot'' and ''bar''.

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.



-N , --timestamping

Turn on time-stamping.



-S , --server-response

Print the headers sent by HTTP servers and responses sent by FTP servers.



--spider

When invoked with this option, Wget will behave as a Web spider, which means that it will not download the pages, just check that they are there. For example, you can use Wget to check your bookmarks:

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.



-T seconds , --timeout=seconds

Set the network timeout to seconds seconds. This is equivalent to specifying --dns-timeout, --connect-timeout, and --read-timeout, all at the same time.

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.



--dns-timeout=seconds

Set the DNS lookup timeout to seconds seconds. DNS lookups that don't complete within the specified time will fail. By default, there is no timeout on DNS lookups, other than that implemented by system libraries.



--connect-timeout=seconds

Set the connect timeout to seconds seconds. TCP connections that take longer to establish will be aborted. By default, there is no connect timeout, other than that implemented by system libraries.



--read-timeout=seconds

Set the read (and write) timeout to seconds seconds. The ''time'' of this timeout refers idle time: if, at any point in the download, no data is received for more than the specified number of seconds, reading fails and the download is restarted. This option does not directly affect the duration of the entire download.

Of course, the remote server may choose to terminate the connection sooner than this option requires. The default read timeout is 900 seconds.



--limit-rate=amount

Limit the download speed to amount bytes per second. Amount may be expressed in bytes, kilobytes with the k suffix, or megabytes with the m suffix. For example, --limit-rate=20k will limit the retrieval rate to 20KB/s. This is useful when, for whatever reason, you don't want Wget to consume the entire available bandwidth.

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.



-w seconds , --wait=seconds

Wait the specified number of seconds between the retrievals. Use of this option is recommended, as it lightens the server load by making the requests less frequent. Instead of in seconds, the time can be specified in minutes using the "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. The waiting interval specified by this function is influenced by "--random-wait", which see.



--waitretry=seconds

If you don't want Wget to wait between every retrieval, but only between retries of failed downloads, you can use this option. Wget will use linear backoff, waiting 1 second after the first failure on a given file, then waiting 2 seconds after the second failure on that file, up to the maximum number of seconds you specify. Therefore, a value of 10 will actually make Wget wait up to (1 + 2 + ... + 10) = 55 seconds per file.

Note that this option is turned on by default in the global wgetrc file.



--random-wait

Some web sites may perform log analysis to identify retrieval programs such as Wget by looking for statistically significant similarities in the time between requests. This option causes the time between requests to vary between 0.5 and 1.5 * wait seconds, where wait was specified using the --wait option, in order to mask Wget's presence from such analysis.

A 2001 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.



--no-proxy

Don't use proxies, even if the appropriate *_proxy environment variable is defined.

For more information about the use of proxies with Wget,



-Q quota , --quota=quota

Specify download quota for automatic retrievals. The value can be specified in bytes (default), kilobytes (with k suffix), or megabytes (with m suffix).

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.



--no-dns-cache

Turn off caching of DNS lookups. Normally, Wget remembers the IP addresses it looked up from DNS so it doesn't have to repeatedly contact the DNS server for the same (typically small) set of hosts it retrieves from. This cache exists in memory only; a new Wget run will contact DNS again.

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.



--restrict-file-names=mode

Change which characters found in remote URLs may show up in local file names generated from those URLs. Characters that are restricted by this option are escaped, i.e. replaced with %HH, where HH is the hexadecimal number that corresponds to the restricted character.

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.



-4 , --inet4-only , -6 , --inet6-only

Force connecting to IPv4 or IPv6 addresses. With --inet4-only or -4, Wget will only connect to IPv4 hosts, ignoring AAAA records in DNS , and refusing to connect to IPv6 addresses specified in URLs. Conversely, with --inet6-only or -6, Wget will only connect to IPv6 hosts and ignore A records and IPv4 addresses.

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 responds with both IPv4 and IPv6 addresses, Wget will them in sequence until it finds one it can connect to. (Also see "--prefer-family" option described below.)

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 at the same time. Neither option is available in Wget compiled without IPv6 support.



--prefer-family=IPv4/IPv6/none

When given a choice of several addresses, connect to the addresses with specified address family first. IPv4 addresses are preferred by default.

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.



--retry-connrefused

Consider ''connection refused'' a transient error and try again. Normally Wget gives up on a URL when it is unable to connect to the site because failure to connect is taken as a sign that the server is not running at all and that retries would not help. This option is for mirroring unreliable sites whose servers tend to disappear for short periods of time.



--user=user , --password=password

Specify the username user and password password for both FTP and HTTP file retrieval. These parameters can be overridden using the --ftp-user and --ftp-password options for FTP connections and the --http-user and --http-password options for HTTP connections.



Directory Options

-nd , --no-directories

Do not create a hierarchy of directories when retrieving recursively. With this option turned on, all files will get saved to the current directory, without clobbering (if a name shows up more than once, the filenames will get extensions .n).



-x , --force-directories

The opposite of -nd---create a hierarchy of directories, even if one would not have been created otherwise. E.g. wget -x http://fly.srk.fer.hr/robots.txt will save the downloaded file to fly.srk.fer.hr/robots.txt.



-nH , --no-host-directories

Disable generation of host-prefixed directories. By default, invoking Wget with -r http://fly.srk.fer.hr/ will create a structure of directories beginning with fly.srk.fer.hr/. This option disables such behavior.



--protocol-directories

Use the protocol name as a directory component of local file names. For example, with this option, wget -r http://host will save to http/host/... rather than just to host/....



--cut-dirs=number

Ignore number directory components. This is useful for getting a fine-grained control over the directory where recursive retrieval will be saved.

Take, for example, the directory at ftp://ftp.xemacs.org/pub/xemacs/. If you retrieve it with -r, it will be saved locally under ftp.xemacs.org/pub/xemacs/. While the -nH option can remove the ftp.xemacs.org/ part, you are still stuck with pub/xemacs. This is where --cut-dirs comes in handy; it makes Wget not ''see'' number remote directory components. Here are several examples of how --cut-dirs option works.



-P prefix , --directory-prefix=prefix

Set directory prefix to prefix. The directory prefix is the directory where all other files and subdirectories will be saved to, i.e. the top of the retrieval tree. The default is . (the current directory).

HTTP Options



-E ,--html-extension

If a file of type application/xhtml+xml or text/html is downloaded and the URL does not end with the regexp \.[Hh][Tt][Mm][Ll]?, this option will cause the suffix .html to be appended to the local filename. This is useful, for instance, when you're mirroring a remote site that uses .asp pages, but you want the mirrored pages to be viewable on your stock Apache server. Another good use for this is when you're downloading CGI-generated materials. A URL like http://site.com/article.cgi?25 will be saved as article.cgi?25.html.

Note that filenames changed in this way will be re-downloaded every time you re-mirror a site, because Wget can't tell that the local X.html file corresponds to remote URL X (since it doesn't yet know that the URL produces output of type text/html or application/xhtml+xml. To prevent this re-downloading, you must use -k and -K so that the original version of the file will be saved as X.orig.



--http-user=user , --http-password=password

Specify the username user and password password on an HTTP server. According to the type of the challenge, Wget will encode them using either the "basic" (insecure) or the "digest" authentication scheme.

Another way to specify username and password is in the URL itself. Either method reveals your password to anyone who bothers to run "ps". To prevent the passwords from being seen, store them in .wgetrc or .netrc, and make sure to protect those files from other users with "chmod". If the passwords are really important, do not leave them lying in those files either---edit the files and delete them after Wget has started the download.



--no-cache

Disable server-side cache. In this case, Wget will send the remote server an appropriate directive (Pragma: no-cache) to get the file from the remote service, rather than returning the cached version. This is especially useful for retrieving and flushing out-of-date documents on proxy servers.

Caching is allowed by default.



--no-cookies

Disable the use of cookies. Cookies are a mechanism for maintaining server-side state. The server sends the client a cookie using the "Set-Cookie" header, and the client responds with the same cookie upon further requests. Since cookies allow the server owners to keep track of visitors and for sites to exchange this information, some consider them a breach of privacy. The default is to use cookies; however, storing cookies is not on by default.



--load-cookies file

Load cookies from file before the first HTTP retrieval. file is a textual file in the format originally used by Netscape's cookies.txt file.

You will typically use this option when mirroring sites that require that you be logged in to access some or all of their content. The login process typically works by the web server issuing an HTTP cookie upon receiving and verifying your credentials. The cookie is then resent by the browser when accessing that part of the site, and so proves your identity.

Mirroring such a site requires Wget to send the same cookies your browser sends when communicating with the site. This is achieved by --load-cookies---simply point Wget to the location of the cookies.txt file, and it will send the same cookies your browser would send in the same situation.



Different browsers keep textual cookie files in different locations:

Netscape 4.x.

The cookies are in ~/.netscape/cookies.txt.



Mozilla and Netscape 6.x.

Mozilla's cookie file is also named cookies.txt, located somewhere under ~/.mozilla, in the directory of your profile. The full path usually ends up looking somewhat like ~/.mozilla/default/some-weird-string/cookies.txt.



Internet Explorer

You can produce a cookie file Wget can use by using the File menu, Import and Export, Export Cookies. This has been tested with Internet Explorer 5; it is not guaranteed to work with earlier versions.



Other browsers.

If you are using a different browser to create your cookies, --load-cookies will only work if you can locate or produce a cookie file in the Netscape format that Wget expects.



If you cannot use --load-cookies, there might still be an alternative. If your browser supports a ''cookie manager'', you can use it to view the cookies used when accessing the site you're mirroring. Write down the name and value of the cookie, and manually instruct Wget to send those cookies, bypassing the ''official'' cookie support:

wget --no-cookies --header "Cookie: ="



--save-cookies file

Save cookies to file before exiting. This will not save cookies that have expired or that have no expiry time (so-called ''session cookies''), but also see --keep-session-cookies.



--keep-session-cookies

When specified, causes --save-cookies to also save session cookies. Session cookies are normally not saved because they are meant to be kept in memory and forgotten when you exit the browser. Saving them is useful on sites that require you to log in or to visit the home page before you can access some pages. With this option, multiple Wget runs are considered a single browser session as far as the site is concerned.

Since the cookie file format does not normally carry session cookies, Wget marks them with an expiry timestamp of 0. Wget's --load-cookies recognizes those as session cookies, but it might confuse other browsers. Also note that cookies so loaded will be treated as other session cookies, which means that if you want --save-cookies to preserve them again, you must use --keep-session-cookies again.



--ignore-length

Unfortunately, some HTTP servers ( CGI programs, to be more precise) send out bogus "Content-Length" headers, which makes Wget go wild, as it thinks not all the document was retrieved. You can spot this syndrome if Wget retries getting the same document again and again, each time claiming that the (otherwise normal) connection has closed on the very same byte.

With this option, Wget will ignore the "Content-Length" header---as if it never existed.



--header=header-line

Send header-line along with the rest of the headers in each HTTP request. The supplied header is sent as-is, which means it must contain name and value separated by colon, and must not contain newlines.

You may define more than one additional header by specifying --header more than once.



wget --header='Accept-Charset: iso-8859-2' \

--header='Accept-Language: hr' \

http://fly.srk.fer.hr/

Specification of an empty string as the header value will clear all previous user-defined headers.

As of Wget 1.10, this option can be used to override headers otherwise generated automatically. This example instructs Wget to connect to localhost, but to specify foo.bar in the "Host" header:



wget --header="Host: foo.bar" http://localhost/

In versions of Wget prior to 1.10 such use of --header caused sending of duplicate headers.



--proxy-user=user , --proxy-password=password

Specify the username user and password password for authentication on a proxy server. Wget will encode them using the "basic" authentication scheme.

Security considerations similar to those with --http-password pertain here as well.



--referer=url

Include 'Referer: url' header in HTTP request. Useful for retrieving documents with server-side processing that assume they are always being retrieved by interactive web browsers and only come out properly when Referer is set to one of the pages that point to them.



--save-headers

Save the headers sent by the HTTP server to the file, preceding the actual contents, with an empty line as the separator.



-U agent-string , --user-agent=agent-string

Identify as agent-string to the HTTP server.

The HTTP protocol allows the clients to identify themselves using a "User-Agent" header field. This enables distinguishing the WWW software, usually for statistical purposes or for tracing of protocol violations. Wget normally identifies as Wget/version, version being the current version number of Wget.

However, some sites have been known to impose the policy of tailoring the output according to the "User-Agent"-supplied information. While this is not such a bad idea in theory, it has been abused by servers denying information to clients other than (historically) Netscape or, more frequently, Microsoft Internet Explorer. This option allows you to change the "User-Agent" line issued by Wget. Use of this option is discouraged, unless you really know what you are doing.

Specifying empty user agent with --user-agent="" instructs Wget not to send the "User-Agent" header in HTTP requests.



--post-data=string , --post-file=file

Use POST as the method for all HTTP requests and send the specified data in the request body. "--post-data" sends string as data, whereas "--post-file" sends the contents of file. Other than that, they work in exactly the same way.

Please be aware that Wget needs to know the size of the POST data in advance. Therefore the argument to "--post-file" must be a regular file; specifying a FIFO or something like /dev/stdin won't work. It's not quite clear how to work around this limitation inherent in HTTP/1 .0. Although HTTP/1 .1 introduces chunked transfer that doesn't require knowing the request length in advance, a client can't use chunked unless it knows it's talking to an HTTP/1 .1 server. And it can't know that until it receives a response, which in turn requires the request to have been completed -- a chicken-and-egg problem.

Note: if Wget is redirected after the POST request is completed, it will not send the POST data to the redirected URL . This is because URLs that process POST often respond with a redirection to a regular page, which does not desire or accept POST . It is not completely clear that this behavior is optimal; if it doesn't work out, it might be changed in the future.

This example shows how to log to a server using POST and then proceed to download the desired pages, presumably only accessible to authorized users:



# Log in to the server. This can be done only once.

wget --save-cookies cookies.txt \

--post-data 'user=foo&password=bar' \

http://server.com/auth.php


# Now grab the page or pages we care about.

wget --load-cookies cookies.txt \

-p http://server.com/interesting/article.php


If the server is using session cookies to track user authentication, the above will not work because --save-cookies will not save them (and neither will browsers) and the cookies.txt file will be empty. In that case use --keep-session-cookies along with --save-cookies to force saving of session cookies.

HTTPS ( SSL/TLS ) Options

To support encrypted HTTP ( HTTPS ) downloads, Wget must be compiled with an external SSL library, currently OpenSSL. If Wget is compiled without SSL support, none of these options are available.



--secure-protocol=protocol

Choose the secure protocol to be used. Legal values are auto, SSLv2, SSLv3, and TLSv1. If auto is used, the SSL library is given the liberty of choosing the appropriate protocol automatically, which is achieved by sending an SSLv2 greeting and announcing support for SSLv3 and TLSv1. This is the default.

Specifying SSLv2, SSLv3, or TLSv1 forces the use of the corresponding protocol. This is useful when talking to old and buggy SSL server implementations that make it hard for OpenSSL to choose the correct protocol version. Fortunately, such servers are quite rare.



--no-check-certificate

Don't check the server certificate against the available certificate authorities. Also don't require the URL host name to match the common name presented by the certificate.

As of Wget 1.10, the default is to verify the server's certificate against the recognized certificate authorities, breaking the SSL handshake and aborting the download if the verification fails. Although this provides more secure downloads, it does break interoperability with some sites that worked with previous Wget versions, particularly those using self-signed, expired, or otherwise invalid certificates. This option forces an ''insecure'' mode of operation that turns the certificate verification errors into warnings and allows you to proceed.



If you encounter ''certificate verification'' errors or ones saying that ''common name doesn't match requested host name'', you can use this option to bypass the verification and proceed with the download. Only use this option if you are otherwise convinced of the site's authenticity, or if you really don't care about the validity of its certificate. It is almost always a bad idea not to check the certificates when transmitting confidential or important data.



--certificate=file

Use the client certificate stored in file. This is needed for servers that are configured to require certificates from the clients that connect to them. Normally a certificate is not required and this switch is optional.



--certificate-type=type

Specify the type of the client certificate. Legal values are PEM (assumed by default) and DER , also known as ASN1 .



--private-key=file

Read the private key from file. This allows you to provide the private key in a file separate from the certificate.



--private-key-type=type

Specify the type of the private key. Accepted values are PEM (the default) and DER .



--ca-certificate=file

Use file as the file with the bundle of certificate authorities ('' CA '') to verify the peers. The certificates must be in PEM format.

Without this option Wget looks for CA certificates at the system-specified locations, chosen at OpenSSL installation time.



--ca-directory=directory

Specifies directory containing CA certificates in PEM format. Each file contains one CA certificate, and the file name is based on a hash value derived from the certificate. This is achieved by processing a certificate directory with the "c_rehash" utility supplied with OpenSSL. Using --ca-directory is more efficient than --ca-certificate when many certificates are installed because it allows Wget to fetch certificates on demand.

Without this option Wget looks for CA certificates at the system-specified locations, chosen at OpenSSL installation time.



--random-file=file

Use file as the source of random data for seeding the pseudo-random number generator on systems without /dev/random.

On such systems the SSL library needs an external source of randomness to initialize. Randomness may be provided by EGD (see --egd-file below) or read from an external source specified by the user. If this option is not specified, Wget looks for random data in $RANDFILE or, if that is unset, in $HOME/.rnd. If none of those are available, it is likely that SSL encryption will not be usable.



If you're getting the ''Could not seed OpenSSL PRNG ; disabling SSL .'' error, you should provide random data using some of the methods described above.



--egd-file=file

Use file as the EGD socket. EGD stands for Entropy Gathering Daemon, a user-space program that collects data from various unpredictable system sources and makes it available to other programs that might need it. Encryption software, such as the SSL library, needs sources of non-repeating randomness to seed the random number generator used to produce cryptographically strong keys.

OpenSSL allows the user to specify his own source of entropy using the "RAND_FILE" environment variable. If this variable is unset, or if the specified file does not produce enough randomness, OpenSSL will read random data from EGD socket specified using this option.



If this option is not specified (and the equivalent startup command is not used), EGD is never contacted. EGD is not needed on modern Unix systems that support /dev/random.



FTP Options

--ftp-user=user , --ftp-password=password

Specify the username user and password password on an FTP server. Without this, or the corresponding startup option, the password defaults to -wget@, normally used for anonymous FTP .

Another way to specify username and password is in the URL itself. Either method reveals your password to anyone who bothers to run "ps". To prevent the passwords from being seen, store them in .wgetrc or .netrc, and make sure to protect those files from other users with "chmod". If the passwords are really important, do not leave them lying in those files either---edit the files and delete them after Wget has started the download.



--no-remove-listing

Don't remove the temporary .listing files generated by FTP retrievals. Normally, these files contain the raw directory listings received from FTP servers. Not removing them can be useful for debugging purposes, or when you want to be able to easily check on the contents of remote server directories (e.g. to verify that a mirror you're running is complete).

Note that even though Wget writes to a known filename for this file, this is not a security hole in the scenario of a user making .listing a symbolic link to /etc/passwd or something and asking "root" to run Wget in his or her directory. Depending on the options used, either Wget will refuse to write to .listing, making the globbing/recursion/time-stamping operation fail, or the symbolic link will be deleted and replaced with the actual .listing file, or the listing will be written to a .listing.number file.

Even though this situation isn't a problem, though, "root" should never run Wget in a non-trusted user's directory. A user could do something as simple as linking index.html to /etc/passwd and asking "root" to run Wget with -N or -r so the file will be overwritten.



--no-glob

Turn off FTP globbing. Globbing refers to the use of shell-like special characters (wildcards), like *, ?, [ and ] to retrieve more than one file from the same directory at once, like:

wget ftp://gnjilux.srk.fer.hr/*.msg

By default, globbing will be turned on if the URL contains a globbing character. This option may be used to turn globbing on or off permanently.

You may have to quote the URL to protect it from being expanded by your shell. Globbing makes Wget look for a directory listing, which is system-specific. This is why it currently works only with Unix FTP servers (and the ones emulating Unix "ls" output).



--no-passive-ftp

Disable the use of the passive FTP transfer mode. Passive FTP mandates that the client connect to the server to establish the data connection rather than the other way around.

If the machine is connected to the Internet directly, both passive and active FTP should work equally well. Behind most firewall and NAT configurations passive FTP has a better chance of working. However, in some rare firewall configurations, active FTP actually works when passive FTP doesn't. If you suspect this to be the case, use this option, or set "passive_ftp=off" in your init file.



--retr-symlinks

Usually, when retrieving FTP directories recursively and a symbolic link is encountered, the linked-to file is not downloaded. Instead, a matching symbolic link is created on the local filesystem. The pointed-to file will not be downloaded unless this recursive retrieval would have encountered it separately and downloaded it anyway.

When --retr-symlinks is specified, however, symbolic links are traversed and the pointed-to files are retrieved. At this time, this option does not cause Wget to traverse symlinks to directories and recurse through them, but in the future it should be enhanced to do this.

Note that when retrieving a file (not a directory) because it was specified on the command-line, rather than because it was recursed to, this option has no effect. Symbolic links are always traversed in this case.



--no-http-keep-alive

Turn off the ''keep-alive'' feature for HTTP downloads. Normally, Wget asks the server to keep the connection open so that, when you download more than one document from the same server, they get transferred over the same TCP connection. This saves time and at the same time reduces the load on the server.

This option is useful when, for some reason, persistent (keep-alive) connections don't work for you, for example due to a server bug or due to the inability of server-side scripts to cope with the connections.



Recursive Retrieval Options

-r , --recursive

Turn on recursive retrieving.



-l depth , --level=depth

Specify recursion maximum depth level depth. The default maximum depth is 5.



--delete-after

This option tells Wget to delete every single file it downloads, after having done so. It is useful for pre-fetching popular pages through a proxy, e.g.:

wget -r -nd --delete-after http://whatever.com/~popular/page/

The -r option is to retrieve recursively, and -nd to not create directories.

Note that --delete-after deletes files on the local machine. It does not issue the DELE command to remote FTP sites, for instance. Also note that when --delete-after is specified, --convert-links is ignored, so .orig files are simply not created in the first place.



-k , --convert-links

After the download is complete, convert the links in the document to make them suitable for local viewing. This affects not only the visible hyperlinks, but any part of the document that links to external content, such as embedded images, links to style sheets, hyperlinks to non-HTML content, etc.

Each link will be changed in one of the two ways:

*

The links to files that have been downloaded by Wget will be changed to refer to the file they point to as a relative link.



Example: if the downloaded file /foo/doc.html links to /bar/img.gif, also downloaded, then the link in doc.html will be modified to point to ../bar/img.gif. This kind of transformation works reliably for arbitrary combinations of directories.

*

The links to files that have not been downloaded by Wget will be changed to include host name and absolute path of the location they point to.



Example: if the downloaded file /foo/doc.html links to /bar/img.gif (or to ../bar/img.gif), then the link in doc.html will be modified to point to http://hostname/bar/img.gif.

Because of this, local browsing works reliably: if a linked file was downloaded, the link will refer to its local name; if it was not downloaded, the link will refer to its full Internet address rather than presenting a broken link. The fact that the former links are converted to relative links ensures that you can move the downloaded hierarchy to another directory.

Note that only at the end of the download can Wget know which links have been downloaded. Because of that, the work done by -k will be performed at the end of all the downloads.



-K , --backup-converted

When converting a file, back up the original version with a .orig suffix. Affects the behavior of -N.



-m , --mirror

Turn on options suitable for mirroring. This option turns on recursion and time-stamping, sets infinite recursion depth and keeps FTP directory listings. It is currently equivalent to -r -N -l inf --no-remove-listing.



-p , --page-requisites

This option causes Wget to download all the files that are necessary to properly display a given HTML page. This includes such things as inlined images, sounds, and referenced stylesheets.

Ordinarily, when downloading a single HTML page, any requisite documents that may be needed to display it properly are not downloaded. Using -r together with -l can help, but since Wget does not ordinarily distinguish between external and inlined documents, one is generally left with ''leaf documents'' that are missing their requisites.



--strict-comments

Turn on strict parsing of HTML comments. The default is to terminate comments at the first occurrence of -->.

According to specifications, HTML comments are expressed as SGML declarations. Declaration is special markup that begins with , such as , that may contain comments between a pair of -- delimiters. HTML comments are ''empty declarations'', SGML declarations without any non-comment text. Therefore, is a valid comment, and so is , but is not.



On the other hand, most HTML writers don't perceive comments as anything other than text delimited with , which is not quite the same. For example, something like works as a valid comment as long as the number of dashes is a multiple of four (!). If not, the comment technically lasts until the next --, which may be at the other end of the document. Because of this, many popular browsers completely ignore the specification and implement what users have come to expect: comments delimited with .



Until version 1.9, Wget interpreted comments strictly, which resulted in missing links in many web pages that displayed fine in browsers, but had the misfortune of containing non-compliant comments. Beginning with version 1.9, Wget has joined the ranks of clients that implements ''naive'' comments, terminating each comment at the first occurrence of -->.

If, for whatever reason, you want strict comment parsing, use this option to turn it on.



Recursive Accept/Reject Options



-A acclist --accept acclist



-R rejlist --reject rejlist

Specify comma-separated lists of file name suffixes or patterns to accept or reject (@pxref{Types of Files} for more details).



-D domain-list

--domains=domain-list

Set domains to be followed. domain-list is a comma-separated list of domains. Note that it does not turn on -H.



--exclude-domains domain-list

Specify the domains that are not to be followed..



--follow-ftp

Follow FTP links from HTML documents. Without this option, Wget will ignore all the FTP links.



--follow-tags=list

Wget has an internal table of HTML tag / attribute pairs that it considers when looking for linked documents during a recursive retrieval. If a user wants only a subset of those tags to be considered, however, he or she should be specify such tags in a comma-separated list with this option.



--ignore-tags=list

This is the opposite of the --follow-tags option. To skip certain HTML tags when recursively looking for documents to download, specify them in a comma-separated list.

In the past, this option was the best bet for downloading a single page and its requisites, using a command-line like:



wget --ignore-tags=a,area -H -k -K -r http:///

However, the author of this option came across a page with tags like "" and came to the realization that specifying tags to ignore was not enough. One can't just tell Wget to ignore "", because then stylesheets will not be downloaded. Now the best bet for downloading a single page and its requisites is the dedicated --page-requisites option.



-H , --span-hosts

Enable spanning across hosts when doing recursive retrieving.



-L , --relative

Follow relative links only. Useful for retrieving a specific home page without any distractions, not even those from the same hosts.



-I list , --include-directories=list

Specify a comma-separated list of directories you wish to follow when downloading (@pxref{Directory-Based Limits} for more details.) Elements of list may contain wildcards.



-X list , --exclude-directories=list

Specify a comma-separated list of directories you wish to exclude from download (@pxref{Directory-Based Limits} for more details.) Elements of list may contain wildcards.



-np , --no-parent

Do not ever ascend to the parent directory when retrieving recursively. This is a useful option, since it guarantees that only the files below a certain hierarchy will be downloaded.



Examples

The examples are divided into three sections loosely based on their complexity.



Simple Usage

Say you want to download a URL . Just type:

wget http://fly.srk.fer.hr/



But what will happen if the connection is slow, and the file is lengthy? The connection will probably fail before the whole file is retrieved, more than once. In this case, Wget will try getting the file until it either gets the whole of it, or exceeds the default number of retries (this being 20). It is easy to change the number of tries to 45, to insure that the whole file will arrive safely:

wget --tries=45 http://fly.srk.fer.hr/jpg/flyweb.jpg



Now let's leave Wget to work in the background, and write its progress to log file log. It is tiring to type --tries, so we shall use -t.

wget -t 45 -o log http://fly.srk.fer.hr/jpg/flyweb.jpg &



The ampersand at the end of the line makes sure that Wget works in the background. To unlimit the number of retries, use -t inf.



The usage of FTP is as simple. Wget will take care of login and password.

wget ftp://gnjilux.srk.fer.hr/welcome.msg



If you specify a directory, Wget will retrieve the directory listing, parse it and convert it to HTML . Try:

wget ftp://ftp.gnu.org/pub/gnu/links index.html



Advanced Usage

You have a file that contains the URLs you want to download? Use the -i switch:

wget -i



If you specify - as file name, the URLs will be read from standard input.

Create a five levels deep mirror image of the GNU web site, with the same directory structure the original has, with only one try per document, saving the log of the activities to gnulog:

wget -r http://www.gnu.org/ -o gnulog



The same as the above, but convert the links in the HTML files to point to local files, so you can view the documents off-line:

wget --convert-links -r http://www.gnu.org/ -o gnulog



Retrieve only one HTML page, but make sure that all the elements needed for the page to be displayed, such as inline images and external style sheets, are also downloaded. Also make sure the downloaded page references the downloaded links.



wget -p --convert-links http://www.server.com/dir/page.html

The HTML page will be saved to www.server.com/dir/page.html, and the images, stylesheets, etc., somewhere under www.server.com/, depending on where they were on the remote server.



The same as the above, but without the www.server.com/ directory. In fact, I don't want to have all those random server directories anyway---just save all those files under a download/ subdirectory of the current directory.



wget -p --convert-links -nH -nd -Pdownload http://www.server.com/dir/page.html



Retrieve the index.html of www.lycos.com, showing the original server headers:

wget -S http://www.lycos.com/



Save the server headers with the file, perhaps for post-processing.

wget --save-headers http://www.lycos.com/

more index.html



Retrieve the first two levels of wuarchive.wustl.edu, saving them to /tmp.

wget -r -l2 -P/tmp ftp://wuarchive.wustl.edu/



You want to download all the GIFs from a directory on an HTTP server. You tried wget http://www.server.com/dir/*.gif, but that didn't work because HTTP retrieval does not support globbing. In that case, use:

wget -r -l1 --no-parent -A.gif http://www.server.com/dir/



More verbose, but the effect is the same. -r -l1 means to retrieve recursively, with maximum depth of 1. --no-parent means that references to the parent directory are ignored, and -A.gif means to download only the GIF files. -A "*.gif" would have worked too.



Suppose you were in the middle of downloading, when Wget was interrupted. Now you do not want to clobber the files already present. It would be:

wget -nc -r http://www.gnu.org/



If you want to encode your own username and password to HTTP or FTP , use the appropriate URL syntax.



wget ftp://hniksic:mypassword@unix.server.com/.emacs

Note, however, that this usage is not advisable on multi-user systems because it reveals your password to anyone who looks at the output of "ps".



You would like the output documents to go to standard output instead of to files?

wget -O - http://jagor.srce.hr/ http://www.srce.hr/



You can also combine the two options and make pipelines to retrieve the documents from remote hotlists:

wget -O - http://cool.list.com/ | wget --force-html -i -



Very Advanced Usage

If you wish Wget to keep a mirror of a page (or FTP subdirectories), use --mirror (-m), which is the shorthand for -r -l inf -N. You can put Wget in the crontab file asking it to recheck a site each Sunday:



crontab

0 0 * * 0 wget --mirror http://www.gnu.org/ -o /home/me/weeklog

In addition to the above, you want the links to be converted for local viewing. But, after having read this manual, you know that link conversion doesn't play well with timestamping, so you also want Wget to back up the original HTML files before the conversion. Wget invocation would look like this:



wget --mirror --convert-links --backup-converted http://www.gnu.org/ -o /home/me/weeklog



But you've also noticed that local viewing doesn't work all that well when HTML files are saved under extensions other than .html, perhaps because they were served as index.cgi. So you'd like Wget to rename all the files served with content-type text/html or application/xhtml+xml to name.html.



wget --mirror --convert-links --backup-converted \

--html-extension -o /home/me/weeklog \

http://www.gnu.org/




Or, with less typing:

wget -m -k -K -E http://www.gnu.org/ -o /home/me/weeklog

Monday, May 5, 2008

What does “> /dev/null 2>&1″ mean?

A lot time we come across a command like
ls > /dev/null 2>&1

This command will produce no output at all, i.e. to STDOUT and no STDERR. The reason for this is that greater-thans (>) in commands like these redirect the program’s output somewhere. In this case, something is being redirected into /dev/null, and something is being redirected into &1.

There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR.

Sometimes they’re not named, they’re numbered. The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don’t name or number one explicitly, you’re talking about STDOUT.

Given that context, the command above is redirecting standard output into /dev/null, which is a place you can dump anything you don’t want (often called the bit-bucket), then redirecting standard error into standard output (you have to put an & in front of the destination when you do this) and since standard output is going to /dev/null hence standard error will also go to /dev/null and hence this command will produce no output

Bash Commands: Useful commands for filesystem, text processing etc

File system
- cat
- chattr
- cd
- chmod
- chown
- chgrp
- cksum
- cmp
- cp
- du
- df
- file
- fsck
- fuser
- ln
- ls
- lsattr
- lsof
- mkdir
- mount
- mv
- pwd
- rm
- rmdir
- split
- touch

Processes
- at
- chroot
- cron
- exit
- kill
- killall
- nice
- pgrep
- pidof
- pkill
- ps
- pstree
- sleep
- time
- top
- wait
- watch

User environment
- env
- finger
- id
- logname
- mesg
- passwd
- su
- sudo
- uname
- uptime
- w
- wall
- who
- whoami
- write

Text processing
- awk
- comm
- cut
- ed
- ex
- fmt
- head
- iconv
- join
- less
- more
- paste
- sed
- sort
- tac
- tail
- tr
- uniq
- wc
- xargs

Shell programming
- alias
- basename
- echo
- expr
- false
- printf
- test
- true
- unset

Networking
- inetd
- netstat
- ping
- rlogin
- nc
- traceroute

Searching
- find
- grep
- strings

Miscellaneous
- banner
- bc
- cal
- clear
- date
- dd
- lp
- man
- size
- tee
- yes

Friday, May 2, 2008

Bash Scripting: If loop example

Example of a simple If loop
#!/bin/bash
a="abcd"
b="abd"
c="ee"
d="ee"

if [ $a = $b ] [ $c = $d ]
then
echo "equal"
echo "We are good"
else
echo "NOT equal"
fi


Example of a if loop with elif
#!/bin/bash
a="Fremont"
if [ $a = "Fremont" ]
then
echo "North California";
elif [ $a = "Los Angeles" ]
then
echo "South California"
else
echo "Out of california"
fi

Bash Scripting: Change case

# Change to lower case
echo "God is great" | tr [A-Z] [a-z]

# Change to uppercase
echo "God is great" | tr [a-z] [A-Z]

How to write a FTP script in BASH Shell

The following is bash script to get files from a FTP server
---------------------------------------------------------------
#!/bin/bash
HOST=ip_address
USER=username
PASSWD=password
FILE=complete file path

ftp -n $HOST << END_SCRIPT
quote USER $USER
quote PASS $PASSWD
get $FILE
quit
END_SCRIPT
---------------------------------------------------------------

Bash Scripting: Special characters

The following are the special characters in BASH. Click on the image to enlarge

Bash Commands: List of all commands

1st2chr: prints the first 2 characters of the input
1stchr: prints the first character of the input
2dig: gets a 2 digit number from the user
DTK: Deception ToolKit
DTK.pl: Deception ToolKit X11 Menu interface
Eterm: X11 video terminal emulator
Etsearch: X11 text search
IPaddr: Get an IP address from the user
WGfixup: Repair an installed WhiteGlove File System
WGin: Install the CD to a hard disk
WGkillprocs: Kill undesirable processes periodically
WGout: Remove the installed operating system - leave the data
WGsec: Secure the operating environment
WGup: Update the hard disk installation
YORN: Get a Y or N from the user

a2p: Awk to Perl translator
addftinfo: add information to troff font files for use with groff
afmtodit: create font files for use with groff -Tps
agetty: terminal interface for multiple consoles
animate: display a sequence of images
ar: create, modify, and extract from archives
arch: display the processor type for this computer
arp: Address Resolution Protocol
arping: Ping using ARP packets
arpspoof: Spoof ARP addresses
as: Assembler
as86: x86 Assembler
atoi: Alphanumeric to integer converter (atoi a -> 97)
atoo: Alphanumeric to octal converter (atoo a -> d=97 o=141 h=61)

badblocks: Search a device for bad blocks
basename: Find the base name for a pathname
bash: The bash command interpreter
bc: An arbitrary precision calculator language
bdftops: Convert to postscript
bison: A compiler compiler
blackbox: The X11 interface used by the bootable CDs
blockdev: Call block device ioctls from the command line
bzip2: File compression utility
bzip2recover: File compression recovery utility

cal: Show a calendar
cardctl: PCMCIA card status display
cardmgr: PCMCIA card manager for detecting POC cards
cat: Concatenate files to the standard output
cdda2wav: Convert cdda format to wave format
cdrecord: Burn a CD-ROM
cfdisk: Curses based disk partition table manipulator
charset: Set an ACM for use in one of the G0/G1 charset slots
chattr: Change file attributes
chgrp: Change group ownership
chkdupexe: Check for duplicate executables
chklastlog: Check lastlog for anomolies
chkproc: Check processes for propriety
chkrootkit: Check for known rootkits
chkwtmp: Check wtmp file for attack patterns
chmod: Change permissions on files
chown: Change ownership of files
chroot: Change root directory
chsh: Change default shell for user
chvt: Change foreground virtual terminal
cksum: Checksum and count the bytes in a file
clear: Clear the screen
clisp: Common Lisp implementation
clock.pl: Display international times in X11
cmp: Compare two files
code: Capture the namespace context for a code fragment
col: Filter reverse line feeds from input
colcrt: Filter nroff output for CRT previewing
colrm: Remove columns from a file
column: Columnate lists
comm: Compare two sorted files line by line
compress: Compress files
consolechars: Load EGA/VGA console screen font, map, application map
convert: Convert between image formats
count: Count from one integer to another by increments
cp: Copy files
cpan: Comprehansive Perl Archive Network
cpp: The C PreProcessor
crlf: Change files to CRLF output from whatever they used to be
crypto: OpenSSL cryptographic library
csplit: Split files into sections determined by context lines
ctrlaltdel: set Ctrl-Alt-Del function
cucipop: Mail pop3 handler
cut: Remove sections from each line of files
cytune: Tune Cyclades driver parameters

d#: Multiply integers
d+: Add integers
da: Date and time
dad: Date addition
dadd: Add integers
date: Date and time
dayadd: Date addition
db: Database create, get, put, hash
dcmp: Date comparrison
dd: Disk dump
dayadd: Date addition
ddate: Converts Gregorian dates to Discordian dates
deallocvt: Deallocate unused virtual terminals
debugfs: Ext2 file system debugger
debugreiserfs: Reiser file system debugger
df: Disk free space listing
dhcpcd: DHCP client daemon
dhcpd: DHCP server daemon
dia: A diagram drawing program
diff: Find differences between two files
diff3: Find differences between three files
dig: Detailed DNS queries
digits: Input a series of N digits (i.e., digits 3)
dir: A pseudonym for 'ls' - list files
dircolors: Colorized directory listing setup
dirname: Strip non-directory suffix from file name
diskwipe: Wipe the contents of a disk out
display: Display an image under X11
dmesg: Print or control the kernel ring buffer
dnsspoof: Spoof DNS packets
dnum: Device number?
dollars: Input a dollars and cents amount
dprofpp: Display perl profile data
dsniff: Sniff network packets from Ethernets
dsub: Substract integers
dtoo: Decimal to octal conversion
du: Disk usage statistics
dump_cis: Display PCMCIA Card Information Structures
dumpe2fs: Dump filesystem information
dumpkeys: Dump keyboard translation tables
dvipdf: Convert DVI files to PDF format

e2fsck: Check an EXT2 filesystem
e2label: Change the label on an ext2 filesystem
echo: Echo things to the display
ed: Line oriented editor
ee: Electric Eyes visualizes image files
egrep: Print lines matching a pattern
eject: Eject the CD-ROM
elvtune: I/O elevator tuner
env: Show the shell environment variables
eps2eps: Convert eps printer files to Postscript
esd: Audio device status information
esd-config: Configure audio devices
esdcat: Get data from audio devices
esdctl: Control audio devices
esddsp: Audio devices DSP processor
esdfilt: Audio devices filter
esdloop: Audio devices loopback
esdmon: Audio devices monitor
esdplay: Audio devices play
esdrec: Audio devices record
esdsample: Audio devices sampling rate
ethereal: Watch ethernet packets graphically from X11
ettercap: Capture ethernet packets
exists: Check for file/directory existence
expand: Convert tabs to spaces
expr: Evaluate numerical expressions
ext2online: EXT2 file system place online
ext2prepare: EXT2 file system preparer
ext2resize: EXT2 file system resizer
extract_compressed_fs: Extract a compressed file system

fadd: Add floating point
faillog: Failure log
FALSE: Retuen a '0' value
fbset: Show and modify frame buffer device settings
fdformat: Format a floppy disk
fdisk: Partition table editor for hard disks
fgconsole: Print the number of the active VT
fgrep: Print lines matching a pattern
file: Determine file type
find: Search a directory hierarchy
find_ethernet: Fine ethernets
find_hdd: Find hard disk drieves
find_scsi: Find SCSI devices
find_usb: Find USB devices
finddns: Find DNS servers for a hostname
findimages: Find graphical; image files
finger.pl: Run the finger program on other systems
fix_bs_and_del: Fix backspace and delete characters
fixmswrd.pl: Fix MS Word files
fixresolv: Build a new /etc/resolv.conf file (fixresolv > /etc/resolv.conf)
fixtime: Fix the time and date using network time protocol
flex: Fast lexical analyzer generator
floursheim: Search the Internet for content
fmt: Simple optimal text formatter
fname: Input a filename
fold: Wrap each input line to fit in specified width
free: Memory usage statistics
fsck: File system checker
fsck.ext2: Check EXT2 file system
fsck.ext3: Check ext3 file system
fsck.minix: Check minix file system
ftl_check: Flash Translation Layer format checker (PC-Flash memory)
ftl_format: Flash Translation Layer formatting utility (PC-Flash memory)
ftp: File Transfer Protocol program
funzip: Filter for extracting from a ZIP archive in a pipe
fuser: Identify processes using files or sockets

g++: GNU project C++ Compiler
gawk: GNU Awk pattern scanning and processing language
gcc: Fnu C Compiler
getent: Get entries from administrative database
getopt: Get options from command lines
getstyle: X11 Style information
gettext: Get text from the user
gettextize: Get the size of an EXT file system
gpasswd: Administer the /etc/group file
gpm: Allow text displays to use mice
gprof: Display call graph profile data
grep: Print lines matching a pattern
grn: Groff preprocessor for gremlin files
groff: Front end for the groff document formatting system
grolbp: Groff driver for Canon CAPSL printers (LBP-4 and LBP-8 series laser printers).
groups: Print the groups a user is in
grpck: Verify integrity of group files
grpconv: Convert to and from shadow passwords and groups
grpunconv: Convert to and from shadow passwords and groups
gs: Ghostscript (postscript interpreter and previewer)
gslj: Ghostscript to Laserjet converter
gslp: Ghostscript to line printer converter
gzexe: Compress executable files in place
gzip: GNU zip and unzip utility

hdparm: Hard disk parameter fetch and set
head: Show the beginning of a file
help: Provide help (if available)
hexdump: Ascii, decimal, hexadecimal, octal dump
host: DNS lookup utility
hostid: Numeric ID of this host
hostname: Name of this host
hpftodit: Create font description files for groff -Tlj4
httrack: Retrieve web sites (Also used by floursheim)
hunt: Packet analysis and session interception
hwclock: Query and set the hardware clock

icmpenum: Enumerate hosts via ICMP probes
iconv: Convert between file codings
id: User, group, ID program
ide_info: Information on the IDE interface
identd: The identification daemon
identify: Describe format and characteristics of image file(s)
ifconfig: Configure IP interface cards
ifdown: Shut down IP network interface
ifport: Select transceiver type for network interface
ifpromisc: Promiscuous mode for ethernet cards
ifup: Start up IP network interface
ifuser: identify destinations routed to a particular network interface
igawk: Gawk with include files
imapd: Internet Message Access Protocol server
import: Capture X screen and save to a file
inetd: Internet daemon master server
info: Read Info documents
infocmp: Compare or print out terminfo descriptions
insmod: Insert loadable kernel module
integer: Input an integer from the user
integers: Input multiple integers from, the user
ipcalc: IP calculator
ipchains: IP firewall mechanism
ipcrm: Interprocess resource remover
ipcs: Information on interprocess communication facilities
ipppd: (ISDN) Point to Point Protocol daemon
iptables: IP firewall mechanism
isapnp: Configure ISA Plug-and-Play devices
isodump: Dump an ISO9660 file system
isoinfo: Information on an ISO9660 file system
isosize: Size of an ISO9660 file system
isovfy: Verify an ISO9660 file system
itoa: Convert integer value to ASCII character

join: Join lines of two files on a common field

kbd_mode: Report or set the keyboard mode
kernelversion: Report the kernel version
kill: Kill processes
killall: Kill all processes meeting a given specification
killramdisk: Kill the RAM disk
kudzu: Configuration change manager

l: list files (abbreviation for ls)
last: List all login dates and times
lastcomm: List last commands typed by users
lastlog: List last time each user logged in
ld: Loader
less: Show files page-by-page and allow search
lftp: Better File Transfer Protocol handler than FTP
libsetup: Setup libraries from select applications
lineup: Line up lines in a file into columns
ll: Long version of ls
ln: Link files into an executable
loadkeys: Load keyboard translation tables
locale: Local configuration information
locate: Locate a file or program in the system
logger: Make entries in the system log
login: The program that lets you log into the system
logname: Name of user logged in
logoutd: Automatic logout daemon
look: Display lines beginning with a given string
losetup: Setup loopback file systems
lprsetup.sh: Setup the line printer
ls: List files
lsattr: List file attributes
lsdev: List devices
lsof: List open files associated with processes
lspci: List PCI cards and types
ltrace: A library call tracer
lynx: A text-based Web interface

m4: Macro preprocessor
mailstats: Display mail statistics
make: Utility to maintain groups of programs
makeinfo: Translate Texinfo documents
makemap: Make a swap file system
makewhatis: Make the whatis database
man: Manual entries for most of the programs listed here
math: Do aritmetic functions
mawk: Pattern scanning and text processing language
mcookie: Generate magic cookies for xauth
md5sum: MD5 cryptographic checksum generator
me: Micro Emacs editor
menu: Menu system turns a directory tree into a menu system
mkdir: Make directories
mke2fs: Make EXT2 file systems
mkfifo: Make FIFOs (named pipes)
mkfs: Make file system
mkfs.bfs: Make BFS file system
mkfs.ext2: Make EXT2 file system
mkfs.minix: Make Minix file system
mkisofs: Make ISO9660 file system
mklost+found: Make lost&Found directory
mkmanifest: Create a shell script (packing list) to restore Unix filenames
mknod: Make a device file
mkpv: Creates PV device
mkraid: Make a RAID file system
mkreiserfs: Make a Reiser fils system
mkswap: Make a swap file system
mmroff: MROFF reference preprocessor
modinfo: Display information about a kernel module
mogrify: Transform an image or sequence of images
montage: Create a composite image by combining separate images
more: Show a file a page at a time (like less)
mount: Mount a file system
mouseconfig: Configure the mouse (almost never needed)
mozilla: Netscape-like web browser
mpg123: Play audio MPEG 1.0/2.0 file (layers 1, 2 and 3)
mtools: Utilities to access DOS disks in Unix
mtr: Network diagnostic tool (ping and traceroute)
mv: Move files
myip: Show my primary IP address
mywhois: Special version of 'whois'

namei: Follow a pathname until a terminal point is found
nasl: Network intrusion detection tool
nasm: Netwide Assembler - portable 80x86 assembler
nc: NetCat - Cat for networks
ncftp: Browser program for the File Transfer Protocol
ndisasm: Netwide Disassembler - 80x86 binary file disassembler
nessus-setup: Setup the Nessus network security scanner
nessusd: Run the scanner from X11
net-install-mandrake-8.1: Network installers for other OSs
net-install-redhat-6.2: Network installers for other OSs
net-install-redhat-7.1: Network installers for other OSs
netadd: Get a full hostname from the user
netconfig: Menu based network configuration program
netdump: Dump network packets
netman: Network-based manual program
netstat: Network usage statistics
newgrp: Change groups
nextname: Make temporary file name (e.g.,nextname testXXXX)
nice: Run a process ot different priority
nl: Number lines of files
nm: List symbols from object files.
nmap: Network mapping utility
nmapfe: X11 front end to nmap
nmbd: NetBIOS name server
nmblookup: NetBIOS name server lookup
nocr: Remove CR from files (changes CRLF to LF only)
noctrl: Remove control characters from files
nohup: Run a process ignoring Hangup (HUP) signals
nolf: Remove linefeeds from files
nonull: Remove null (0) characters from files
noparity: Remove parity bits from filess
noquote: Input a line without shell quote characters
noreps.pl: Remove repetitive lines from a file
npulse: Network pulse taking program
nrepsum: Eliminate duplicate lines and count how many of each
nslookup: Lookup a hostname on a name server
ntop: Daemon for port 3000 to get network traffic information
ntop-config: Confogure ntop
ntpd: Network time protocol daemon
ntpdate: Update time by asking remote NTP servers
number: Input a real number from the user

o#: Octal multiplication
o+: Octal addition
objcopy: Copy and translate object files
objdump: Display information from object files
od: Octal to decminal conversion
oddparity: Set the first bit on all bytes
ok: Ask for an 'ok' confirmation
oldps: Report process status
oneofeach: Get a list of different things
onum: Get an octal number from the user
oo: Open Office
openssl: Secure Socket Layer handler
openvt: Start a program on a new virtual terminal
otod: Convert octal to decimal

pack_cis: Compile PCMCIA Card Information Structures
pan: X11 mail fetch and send program
parted: Partition manipulation program
passwd: Change passwords
paste: Merge lines of files
pathchk: Check whether file names are valid or portable
patmat: Pattern matching virus detection
pcinitrd: Create a PCMCIA initrd ram disk image
pd: Partition table decoder
perl: The perl language
perlcc: Frontend for perl compiler
perldoc: Perl documentation
pic: Compile pictures for troff or TeX
pico: GUI text editor
pidof: Find the process ID of a running program
pilot: File system browser in the style of the Pine Composer
pine: Email program
ping: Send ICMP packets to computers
pinky: Lightweight finger program
pivot_root: Change the root of the file system
pkill: Process killer and signaller
pl2pm: Rough tool translates Perl4 .pl files to Perl5 .pm modules
plipconfig: Fine tune PLIP device parameters
pnpdump: Dump ISA Plug-And-Play devices resource information
pod2html: Convert POD files to html
pod2latex: Convert POD files to latex
pod2man: Convert POD files to man files
pod2text: Convert POD files to text files
pod2usage: Convert POD files to usage files
podchecker: Check POD files
pppd: Point to point protocol daemon
pppdump: Convert PPP record file to readable format
pr: Convert files for the line printer
praliases: Display system mail aliases
printenv: Print all or part of environment
printf: Format and print data
probe: Probes for PCI and other bridge hardware
procinfo: Display system status gathered from /proc
procmgr.pl: X11-based process manager
ps: Process status lister
ps2ascii: Convert postscript to ascii
ps2epsi: Convert postscript to EPS printer format
ps2pdf: Convert postscript to PDF format
psfaddtable: Add a Unicode character table to a console font
psfgettable: Get the Unicode character table from a console font
psfstriptable: Remove embedded Unicode character table from a console font
pstree: Show the process table as a tree structure
pstruct: Dump C structures as generated from cc -g -S stabs
ptadmin.pl: X11-based system administration interface
ptx: Produce a permuted index of file contents
pump: DHCP interface startup
pv.sh: Preview a DVI page in postscript
pwck: Verify integrity of password files
pwconv: convert to and from shadow password files
pwd: Print working directory
pwunconv: Convert to and from shadow password files

qotd.pl: X11 GUI name server lookup program

raidstart: Start a RAID array
refer: Preprocess bibliographic references for groff
reiserfsck: Check a reiser file system
relf: Relinefeed a file
relf2: Relinefeed a file another way
relflab: Relinefeed a file for label printing
reline: Reline a file to 80 columns wide
rename: Rename files
renice: Change the 'nice' level of a running process
resize2fs: EXT2 file system resizer
resize_reiserfs: Reiser file system resizer
resizecons: Change kernel idea of the console size
rev: Reverse lines of a file
rm: Remove a file
rmail: Readmail
rmdir: Remove a directory
rmt: Remote magtape protocol module
ro: Make mounted file systems read-only (default)
route: Update and show packet routing tables
rpcgen: RPC protocol compiler
rpcinfo: Report RPC information
rpm: Red Hat Package Manager
rsync: Faster, flexible replacement for rcp
rw: Make mounted file systems read-write

s2p: Sed to Perl translator
samba: Start SMB services
sash: Stand-alone shell with built-in commands
say: Encrypted chat session talk side of connection
scp: SSH copy program
script: Record terminal input and output to a file
scsi_info: Information on SCSI devices
sdiff: Find and merge differences between files interactively
sdns: Secure DNS server
sed: Stream editor
see: Encrypted chat session listen side of connection
sendmail: Email send and receivbe client (use for send only)
sens: Sensitivity adjustment
seq: Like count
service: Start and stop system services
setfdprm: Set user-provided floppy disk parameters
seticons: Sets the icon images used in Window Maker
setkeycodes: Load kernel scancode-to-keycode mapping
setleds: Set the keyboard leds
setmetamode: Define the keyboard meta key handling
setpci: Configure PCI devices
setsid: Run a program in a new session
setterm: Set terminal attributes
setxkbmap: Set the keyboard using the X keyboard extensions
sfdisk: Partition table manipulator
sftp: Secure (SSH) FTP
sftp-server: Secure (SSH) FTP server
shasum: SHA cryptographic hash checksummer
showcfont: Displays all characters in the current screen font
showkey: Examine the scan codes and keycodes sent by the keyboard
sing: Send packets of various sorts
size: Find the memory size of a program if run
skill: Report process status
slattach: Attach a network interface to a serial line
sleep: Sleep for some number of seconds
sln: Static ln command
smbclient: Windows file sharing client
smbd: Windows file sharing daemon
smbmount: Mount remote Windows file systems
smbpasswd: Set remote Windows file sharing password
smbspool: Rig remote Windows printing
smbstatus: Status of Windows file sharing
smbtar: Back up Windows file shares to tape files
smrsh: Restricted shell for sendmail
snice: Report process status
sniffit: Network traffic sniffer
snort: Network sniffer and intrusion deteciton front end
socklist: List open sockets
soelim: Interpret .so requests in groff input
sort: Sort files
splain: Perl compiler pragma to force verbose warning diagnostics
split: Split a file into parts
sprof: Read and display shared object profiling data
ssh: Secure Shell encrypted communication client
sshd: Secure Shell encrypted communication daemon
ssl: Secure Socket Layer handler
startx: Start X11 running
strace: Trace system calls and signals
strings: Extract strings from a file
strip: Remove unnecessary text from executables
stty: Set tty characteristics
stuff: Help file from the PLAC disk
stunnel: Universal SSL tunnel
su: Switch users
sulogin: Single user login
sum: Add up a column of numbers
swapon: Turn on swapping
swat: Remote management of SMB servers
sync: Write all not-yet-written content to disks
syslogd: System log daemon
sysviuw.pl: View system status information (in X11)
sysvlp.sh: Postscript printer interface

tac: Concatenate and print files in reverse
tack: Terminfo action checker
tail: Show the end of a file
tar: Tape Archiver
tbl: Format tables for troff
tcpdump: Show network packets to the user
tcpkill: Kill an existing TCP connection
tcpspy: Watch TCP connections
tcsh: Another command interpreter
tct-1.06: The coroner's toolkit
tee: Split output to a file and to standard output
telnet: Remote access to computers (insecure)
testparm: Check an smb.conf configuration file
texi2dvi: Convert text to DVi format
tftp: Trivial file transfer protocol
tic: The terminfo entry-description compiler
time.pl: Show time in parts of the world
timezone: Set the time zone
tload: Show load average
toe: Table of (terminfo) entries
tolower: Convert to lower case
top: Show processes sorted by CPU usage over time
touch: Set the file access date on a file
toupper: Convert to upper case
tr: Translate or delete characters
traceroute: Trace a route over the network
track: Interface to httrack
TRUE: Always return true
tset: Set terminal up
tsort: Perform topological sort
tty: What terminal am I running this command from?
tune2fs: Adjust tunable EXT2 filesystem parameters
tunelp: Set various parameters for the lp device
tzselect: Set the time zone

ul: Do underlining
umount: Unmount mounted filesystems
uname: Name of operating system (try uname -a)
unexpand: Convert spaces to tabs
uniq: Remove duplicate lines from a sorted file
unscape: Convert netscape converted input strings to real strings
unzip: Unzip a zipped file
uptime: How long has this computer been up?
urlsnarf: Get a file from a web URL
useradd: Add a user account
userdel: Delete a user account
usermod: Modify a user account
users: List logged in users
usleep: Sleep some number of microseconds
utodos: Convert unix to DOS file content
uudecode: Unix to Unix trnasport decode
uuencode: Unix to Unix trnasport encode
uuidgen: Command-line utility to create a new UUID value
uz: unzip

vdir: like ls -l
vim: Visual editor
vimtutor: Visual editor tutor
vipw: Edit the password or group files
vmstat: Virtual memory statistics
vncconnect: Connect a VNC server to a VNC viewer
vncpasswd: Set password for VNC server
vncserver: Start a VNC server application
vncviewer: VNC client application

w: Who is on the system
wall: Write to all users and terminals
watch: Watch a set of command outputs
wc: Word count
we: Write Enable mounted disks
webget: Get a URL from the web
webser: Start a web server
wget: Get a URL from the web
whatis: Search the whatis database for complete words
whereis: Locate the binary, source, and manual page files for a command
which: If I type a command which program will it run?
whichall: All the programs of that name in my path
whisker: Scans CGI-bin scripts for vulnerabilities
who: Who is logged in
whoami: Who am I (what it my user ID, etc.)?
whois: Lookup information in the Internet Whois database
wipe: Shutdown LAM
wipedisk: Wipe the contents of a disk out
wish: Simple menu interface for X11
wl: Write Lock mounted disks
word: Get a word from the user
words: Get multiple words from the user
write: Write a message to another user

x: Run X11 (if startx fails)
xhost: Allow a remote host to control your X11 session (don't do it)
xkill: Kill X11 windows
xprobe: Find X11 systems and seek vulnerabilities
xrdb: X server resource database utility
xscreensaver: X11 screen saver
xterm: Run a user terminal from X11
xtrace: Trace a program execution
xvidtune: Tune the video display

yacc: Yet another compiler compiler
yes: Send 'y' as output forever
yorn: Get a 'y' or 'n' from the user

zcat: Typoe a compressed file
zcmp: Compare compressed files
zdiff: Do 'diff' on compressed files
zdump: Dump contents of a compressed file
zgrep: Do 'grep' on a compressed file
zic: Time zone compiler
zip: Compress a file