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+# curl tutorial
+
+## Simple Usage
+
+Get the main page from Netscape's web-server:
+
+    curl http://www.netscape.com/
+
+Get the README file the user's home directory at funet's ftp-server:
+
+    curl ftp://ftp.funet.fi/README
+
+Get a web page from a server using port 8000:
+
+    curl http://www.weirdserver.com:8000/
+
+Get a directory listing of an FTP site:
+
+    curl ftp://cool.haxx.se/
+
+Get the definition of curl from a dictionary:
+
+    curl dict://dict.org/m:curl
+
+Fetch two documents at once:
+
+    curl ftp://cool.haxx.se/ http://www.weirdserver.com:8000/
+
+Get a file off an FTPS server:
+
+    curl ftps://files.are.secure.com/secrets.txt
+
+or use the more appropriate FTPS way to get the same file:
+
+    curl --ftp-ssl ftp://files.are.secure.com/secrets.txt
+
+Get a file from an SSH server using SFTP:
+
+    curl -u username sftp://example.com/etc/issue
+
+Get a file from an SSH server using SCP using a private key (not
+password-protected) to authenticate:
+
+    curl -u username: --key ~/.ssh/id_rsa scp://example.com/~/file.txt
+
+Get a file from an SSH server using SCP using a private key
+(password-protected) to authenticate:
+
+    curl -u username: --key ~/.ssh/id_rsa --pass private_key_password
+    scp://example.com/~/file.txt
+
+Get the main page from an IPv6 web server:
+
+    curl "http://[2001:1890:1112:1::20]/"
+
+Get a file from an SMB server:
+
+    curl -u "domain\username:passwd" smb://server.example.com/share/file.txt
+
+## Download to a File
+
+Get a web page and store in a local file with a specific name:
+
+    curl -o thatpage.html http://www.netscape.com/
+
+Get a web page and store in a local file, make the local file get the name of
+the remote document (if no file name part is specified in the URL, this will
+fail):
+
+    curl -O http://www.netscape.com/index.html
+
+Fetch two files and store them with their remote names:
+
+    curl -O www.haxx.se/index.html -O curl.haxx.se/download.html
+
+## Using Passwords
+
+### FTP
+
+To ftp files using name+passwd, include them in the URL like:
+
+    curl ftp://name:passwd@machine.domain:port/full/path/to/file
+
+or specify them with the -u flag like
+
+    curl -u name:passwd ftp://machine.domain:port/full/path/to/file
+
+### FTPS
+
+It is just like for FTP, but you may also want to specify and use SSL-specific
+options for certificates etc.
+
+Note that using `FTPS://` as prefix is the "implicit" way as described in the
+standards while the recommended "explicit" way is done by using FTP:// and the
+`--ftp-ssl` option.
+
+### SFTP / SCP
+
+This is similar to FTP, but you can use the `--key` option to specify a
+private key to use instead of a password. Note that the private key may itself
+be protected by a password that is unrelated to the login password of the
+remote system; this password is specified using the `--pass` option.
+Typically, curl will automatically extract the public key from the private key
+file, but in cases where curl does not have the proper library support, a
+matching public key file must be specified using the `--pubkey` option.
+
+### HTTP
+
+Curl also supports user and password in HTTP URLs, thus you can pick a file
+like:
+
+    curl http://name:passwd@machine.domain/full/path/to/file
+
+or specify user and password separately like in
+
+    curl -u name:passwd http://machine.domain/full/path/to/file
+
+HTTP offers many different methods of authentication and curl supports
+several: Basic, Digest, NTLM and Negotiate (SPNEGO). Without telling which
+method to use, curl defaults to Basic. You can also ask curl to pick the most
+secure ones out of the ones that the server accepts for the given URL, by
+using `--anyauth`.
+
+**Note**! According to the URL specification, HTTP URLs can not contain a user
+and password, so that style will not work when using curl via a proxy, even
+though curl allows it at other times. When using a proxy, you _must_ use the
+`-u` style for user and password.
+
+### HTTPS
+
+Probably most commonly used with private certificates, as explained below.
+
+## Proxy
+
+curl supports both HTTP and SOCKS proxy servers, with optional authentication.
+It does not have special support for FTP proxy servers since there are no
+standards for those, but it can still be made to work with many of them. You
+can also use both HTTP and SOCKS proxies to transfer files to and from FTP
+servers.
+
+Get an ftp file using an HTTP proxy named my-proxy that uses port 888:
+
+    curl -x my-proxy:888 ftp://ftp.leachsite.com/README
+
+Get a file from an HTTP server that requires user and password, using the
+same proxy as above:
+
+    curl -u user:passwd -x my-proxy:888 http://www.get.this/
+
+Some proxies require special authentication. Specify by using -U as above:
+
+    curl -U user:passwd -x my-proxy:888 http://www.get.this/
+
+A comma-separated list of hosts and domains which do not use the proxy can be
+specified as:
+
+    curl --noproxy localhost,get.this -x my-proxy:888 http://www.get.this/
+
+If the proxy is specified with `--proxy1.0` instead of `--proxy` or `-x`, then
+curl will use HTTP/1.0 instead of HTTP/1.1 for any `CONNECT` attempts.
+
+curl also supports SOCKS4 and SOCKS5 proxies with `--socks4` and `--socks5`.
+
+See also the environment variables Curl supports that offer further proxy
+control.
+
+Most FTP proxy servers are set up to appear as a normal FTP server from the
+client's perspective, with special commands to select the remote FTP server.
+curl supports the `-u`, `-Q` and `--ftp-account` options that can be used to
+set up transfers through many FTP proxies. For example, a file can be uploaded
+to a remote FTP server using a Blue Coat FTP proxy with the options:
+
+    curl -u "username@ftp.server Proxy-Username:Remote-Pass"
+      --ftp-account Proxy-Password --upload-file local-file
+      ftp://my-ftp.proxy.server:21/remote/upload/path/
+
+See the manual for your FTP proxy to determine the form it expects to set up
+transfers, and curl's `-v` option to see exactly what curl is sending.
+
+## Ranges
+
+HTTP 1.1 introduced byte-ranges. Using this, a client can request to get only
+one or more subparts of a specified document. Curl supports this with the `-r`
+flag.
+
+Get the first 100 bytes of a document:
+
+    curl -r 0-99 http://www.get.this/
+
+Get the last 500 bytes of a document:
+
+    curl -r -500 http://www.get.this/
+
+Curl also supports simple ranges for FTP files as well. Then you can only
+specify start and stop position.
+
+Get the first 100 bytes of a document using FTP:
+
+    curl -r 0-99 ftp://www.get.this/README
+
+## Uploading
+
+### FTP / FTPS / SFTP / SCP
+
+Upload all data on stdin to a specified server:
+
+    curl -T - ftp://ftp.upload.com/myfile
+
+Upload data from a specified file, login with user and password:
+
+    curl -T uploadfile -u user:passwd ftp://ftp.upload.com/myfile
+
+Upload a local file to the remote site, and use the local file name at the
+remote site too:
+
+    curl -T uploadfile -u user:passwd ftp://ftp.upload.com/
+
+Upload a local file to get appended to the remote file:
+
+    curl -T localfile -a ftp://ftp.upload.com/remotefile
+
+Curl also supports ftp upload through a proxy, but only if the proxy is
+configured to allow that kind of tunneling. If it does, you can run curl in a
+fashion similar to:
+
+    curl --proxytunnel -x proxy:port -T localfile ftp.upload.com
+
+### SMB / SMBS
+
+    curl -T file.txt -u "domain\username:passwd"
+      smb://server.example.com/share/
+
+### HTTP
+
+Upload all data on stdin to a specified HTTP site:
+
+    curl -T - http://www.upload.com/myfile
+
+Note that the HTTP server must have been configured to accept PUT before this
+can be done successfully.
+
+For other ways to do HTTP data upload, see the POST section below.
+
+## Verbose / Debug
+
+If curl fails where it isn't supposed to, if the servers don't let you in, if
+you can't understand the responses: use the `-v` flag to get verbose
+fetching. Curl will output lots of info and what it sends and receives in
+order to let the user see all client-server interaction (but it won't show you
+the actual data).
+
+    curl -v ftp://ftp.upload.com/
+
+To get even more details and information on what curl does, try using the
+`--trace` or `--trace-ascii` options with a given file name to log to, like
+this:
+
+    curl --trace trace.txt www.haxx.se
+
+
+## Detailed Information
+
+Different protocols provide different ways of getting detailed information
+about specific files/documents. To get curl to show detailed information about
+a single file, you should use `-I`/`--head` option. It displays all available
+info on a single file for HTTP and FTP. The HTTP information is a lot more
+extensive.
+
+For HTTP, you can get the header information (the same as `-I` would show)
+shown before the data by using `-i`/`--include`. Curl understands the
+`-D`/`--dump-header` option when getting files from both FTP and HTTP, and it
+will then store the headers in the specified file.
+
+Store the HTTP headers in a separate file (headers.txt in the example):
+
+      curl --dump-header headers.txt curl.haxx.se
+
+Note that headers stored in a separate file can be very useful at a later time
+if you want curl to use cookies sent by the server. More about that in the
+cookies section.
+
+## POST (HTTP)
+
+It's easy to post data using curl. This is done using the `-d <data>` option.
+The post data must be urlencoded.
+
+Post a simple "name" and "phone" guestbook.
+
+    curl -d "name=Rafael%20Sagula&phone=3320780" http://www.where.com/guest.cgi
+
+How to post a form with curl, lesson #1:
+
+Dig out all the `<input>` tags in the form that you want to fill in.
+
+If there's a "normal" post, you use `-d` to post. `-d` takes a full "post
+string", which is in the format
+
+    <variable1>=<data1>&<variable2>=<data2>&...
+
+The 'variable' names are the names set with `"name="` in the `<input>` tags,
+and the data is the contents you want to fill in for the inputs. The data
+*must* be properly URL encoded. That means you replace space with + and that
+you replace weird letters with %XX where XX is the hexadecimal representation
+of the letter's ASCII code.
+
+Example:
+
+(page located at `http://www.formpost.com/getthis/`)
+
+    <form action="post.cgi" method="post">
+    <input name=user size=10>
+    <input name=pass type=password size=10>
+    <input name=id type=hidden value="blablabla">
+    <input name=ding value="submit">
+    </form>
+
+We want to enter user 'foobar' with password '12345'.
+
+To post to this, you enter a curl command line like:
+
+    curl -d "user=foobar&pass=12345&id=blablabla&ding=submit"
+      http://www.formpost.com/getthis/post.cgi
+
+While `-d` uses the application/x-www-form-urlencoded mime-type, generally
+understood by CGI's and similar, curl also supports the more capable
+multipart/form-data type. This latter type supports things like file upload.
+
+`-F` accepts parameters like `-F "name=contents"`. If you want the contents to
+be read from a file, use `@filename` as contents. When specifying a file, you
+can also specify the file content type by appending `;type=<mime type>` to the
+file name. You can also post the contents of several files in one field.  For
+example, the field name 'coolfiles' is used to send three files, with
+different content types using the following syntax:
+
+    curl -F "coolfiles=@fil1.gif;type=image/gif,fil2.txt,fil3.html"
+      http://www.post.com/postit.cgi
+
+If the content-type is not specified, curl will try to guess from the file
+extension (it only knows a few), or use the previously specified type (from an
+earlier file if several files are specified in a list) or else it will use the
+default type 'application/octet-stream'.
+
+Emulate a fill-in form with `-F`. Let's say you fill in three fields in a
+form. One field is a file name which to post, one field is your name and one
+field is a file description. We want to post the file we have written named
+"cooltext.txt". To let curl do the posting of this data instead of your
+favourite browser, you have to read the HTML source of the form page and find
+the names of the input fields. In our example, the input field names are
+'file', 'yourname' and 'filedescription'.
+
+    curl -F "file=@cooltext.txt" -F "yourname=Daniel"
+      -F "filedescription=Cool text file with cool text inside"
+      http://www.post.com/postit.cgi
+
+To send two files in one post you can do it in two ways:
+
+Send multiple files in a single "field" with a single field name:
+
+    curl -F "pictures=@dog.gif,cat.gif" $URL
+
+Send two fields with two field names
+
+    curl -F "docpicture=@dog.gif" -F "catpicture=@cat.gif" $URL
+
+To send a field value literally without interpreting a leading `@` or `<`, or
+an embedded `;type=`, use `--form-string` instead of `-F`. This is recommended
+when the value is obtained from a user or some other unpredictable
+source. Under these circumstances, using `-F` instead of `--form-string` could
+allow a user to trick curl into uploading a file.
+
+## Referrer
+
+An HTTP request has the option to include information about which address
+referred it to the actual page.  Curl allows you to specify the referrer to be
+used on the command line. It is especially useful to fool or trick stupid
+servers or CGI scripts that rely on that information being available or
+contain certain data.
+
+    curl -e www.coolsite.com http://www.showme.com/
+
+## User Agent
+
+An HTTP request has the option to include information about the browser that
+generated the request. Curl allows it to be specified on the command line. It
+is especially useful to fool or trick stupid servers or CGI scripts that only
+accept certain browsers.
+
+Example:
+
+    curl -A 'Mozilla/3.0 (Win95; I)' http://www.nationsbank.com/
+
+Other common strings:
+
+- `Mozilla/3.0 (Win95; I)` - Netscape Version 3 for Windows 95
+- `Mozilla/3.04 (Win95; U)` - Netscape Version 3 for Windows 95
+- `Mozilla/2.02 (OS/2; U)` - Netscape Version 2 for OS/2
+- `Mozilla/4.04 [en] (X11; U; AIX 4.2; Nav)` - Netscape for AIX
+- `Mozilla/4.05 [en] (X11; U; Linux 2.0.32 i586)` - Netscape for Linux
+
+Note that Internet Explorer tries hard to be compatible in every way:
+
+- `Mozilla/4.0 (compatible; MSIE 4.01; Windows 95)` - MSIE for W95
+
+Mozilla is not the only possible User-Agent name:
+
+- `Konqueror/1.0` - KDE File Manager desktop client
+- `Lynx/2.7.1 libwww-FM/2.14` - Lynx command line browser
+
+## Cookies
+
+Cookies are generally used by web servers to keep state information at the
+client's side. The server sets cookies by sending a response line in the
+headers that looks like `Set-Cookie: <data>` where the data part then
+typically contains a set of `NAME=VALUE` pairs (separated by semicolons `;`
+like `NAME1=VALUE1; NAME2=VALUE2;`). The server can also specify for what path
+the "cookie" should be used for (by specifying `path=value`), when the cookie
+should expire (`expire=DATE`), for what domain to use it (`domain=NAME`) and
+if it should be used on secure connections only (`secure`).
+
+If you've received a page from a server that contains a header like:
+
+    Set-Cookie: sessionid=boo123; path="/foo";
+
+it means the server wants that first pair passed on when we get anything in a
+path beginning with "/foo".
+
+Example, get a page that wants my name passed in a cookie:
+
+    curl -b "name=Daniel" www.sillypage.com
+
+Curl also has the ability to use previously received cookies in following
+sessions. If you get cookies from a server and store them in a file in a
+manner similar to:
+
+    curl --dump-header headers www.example.com
+
+... you can then in a second connect to that (or another) site, use the
+cookies from the 'headers' file like:
+
+    curl -b headers www.example.com
+
+While saving headers to a file is a working way to store cookies, it is
+however error-prone and not the preferred way to do this. Instead, make curl
+save the incoming cookies using the well-known netscape cookie format like
+this:
+
+    curl -c cookies.txt www.example.com
+
+Note that by specifying `-b` you enable the "cookie awareness" and with `-L`
+you can make curl follow a location: (which often is used in combination with
+cookies). So that if a site sends cookies and a location, you can use a
+non-existing file to trigger the cookie awareness like:
+
+    curl -L -b empty.txt www.example.com
+
+The file to read cookies from must be formatted using plain HTTP headers OR as
+netscape's cookie file. Curl will determine what kind it is based on the file
+contents.  In the above command, curl will parse the header and store the
+cookies received from www.example.com.  curl will send to the server the
+stored cookies which match the request as it follows the location.  The file
+"empty.txt" may be a nonexistent file.
+
+To read and write cookies from a netscape cookie file, you can set both `-b`
+and `-c` to use the same file:
+
+    curl -b cookies.txt -c cookies.txt www.example.com
+
+## Progress Meter
+
+The progress meter exists to show a user that something actually is
+happening. The different fields in the output have the following meaning:
+
+    % Total    % Received % Xferd  Average Speed          Time             Curr.
+                                   Dload  Upload Total    Current  Left    Speed
+    0  151M    0 38608    0     0   9406      0  4:41:43  0:00:04  4:41:39  9287
+
+From left-to-right:
+
+ - %             - percentage completed of the whole transfer
+ - Total         - total size of the whole expected transfer
+ - %             - percentage completed of the download
+ - Received      - currently downloaded amount of bytes
+ - %             - percentage completed of the upload
+ - Xferd         - currently uploaded amount of bytes
+ - Average Speed Dload - the average transfer speed of the download
+ - Average Speed Upload - the average transfer speed of the upload
+ - Time Total    - expected time to complete the operation
+ - Time Current  - time passed since the invoke
+ - Time Left     - expected time left to completion
+ - Curr.Speed    - the average transfer speed the last 5 seconds (the first
+                   5 seconds of a transfer is based on less time of course.)
+
+The `-#` option will display a totally different progress bar that doesn't
+need much explanation!
+
+## Speed Limit
+
+Curl allows the user to set the transfer speed conditions that must be met to
+let the transfer keep going. By using the switch `-y` and `-Y` you can make
+curl abort transfers if the transfer speed is below the specified lowest limit
+for a specified time.
+
+To have curl abort the download if the speed is slower than 3000 bytes per
+second for 1 minute, run:
+
+    curl -Y 3000 -y 60 www.far-away-site.com
+
+This can very well be used in combination with the overall time limit, so
+that the above operation must be completed in whole within 30 minutes:
+
+    curl -m 1800 -Y 3000 -y 60 www.far-away-site.com
+
+Forcing curl not to transfer data faster than a given rate is also possible,
+which might be useful if you're using a limited bandwidth connection and you
+don't want your transfer to use all of it (sometimes referred to as
+"bandwidth throttle").
+
+Make curl transfer data no faster than 10 kilobytes per second:
+
+    curl --limit-rate 10K www.far-away-site.com
+
+or
+
+    curl --limit-rate 10240 www.far-away-site.com
+
+Or prevent curl from uploading data faster than 1 megabyte per second:
+
+    curl -T upload --limit-rate 1M ftp://uploadshereplease.com
+
+When using the `--limit-rate` option, the transfer rate is regulated on a
+per-second basis, which will cause the total transfer speed to become lower
+than the given number. Sometimes of course substantially lower, if your
+transfer stalls during periods.
+
+## Config File
+
+Curl automatically tries to read the `.curlrc` file (or `_curlrc` file on
+Microsoft Windows systems) from the user's home dir on startup.
+
+The config file could be made up with normal command line switches, but you
+can also specify the long options without the dashes to make it more
+readable. You can separate the options and the parameter with spaces, or with
+`=` or `:`. Comments can be used within the file. If the first letter on a
+line is a `#`-symbol the rest of the line is treated as a comment.
+
+If you want the parameter to contain spaces, you must enclose the entire
+parameter within double quotes (`"`). Within those quotes, you specify a quote
+as `\"`.
+
+NOTE: You must specify options and their arguments on the same line.
+
+Example, set default time out and proxy in a config file:
+
+    # We want a 30 minute timeout:
+    -m 1800
+    # ... and we use a proxy for all accesses:
+    proxy = proxy.our.domain.com:8080
+
+White spaces ARE significant at the end of lines, but all white spaces leading
+up to the first characters of each line are ignored.
+
+Prevent curl from reading the default file by using -q as the first command
+line parameter, like:
+
+    curl -q www.thatsite.com
+
+Force curl to get and display a local help page in case it is invoked without
+URL by making a config file similar to:
+
+    # default url to get
+    url = "http://help.with.curl.com/curlhelp.html"
+
+You can specify another config file to be read by using the `-K`/`--config`
+flag. If you set config file name to `-` it'll read the config from stdin,
+which can be handy if you want to hide options from being visible in process
+tables etc:
+
+    echo "user = user:passwd" | curl -K - http://that.secret.site.com
+
+## Extra Headers
+
+When using curl in your own very special programs, you may end up needing
+to pass on your own custom headers when getting a web page. You can do
+this by using the `-H` flag.
+
+Example, send the header `X-you-and-me: yes` to the server when getting a
+page:
+
+    curl -H "X-you-and-me: yes" www.love.com
+
+This can also be useful in case you want curl to send a different text in a
+header than it normally does. The `-H` header you specify then replaces the
+header curl would normally send. If you replace an internal header with an
+empty one, you prevent that header from being sent. To prevent the `Host:`
+header from being used:
+
+    curl -H "Host:" www.server.com
+
+## FTP and Path Names
+
+Do note that when getting files with a `ftp://` URL, the given path is
+relative the directory you enter. To get the file `README` from your home
+directory at your ftp site, do:
+
+    curl ftp://user:passwd@my.site.com/README
+
+But if you want the README file from the root directory of that very same
+site, you need to specify the absolute file name:
+
+    curl ftp://user:passwd@my.site.com//README
+
+(I.e with an extra slash in front of the file name.)
+
+## SFTP and SCP and Path Names
+
+With sftp: and scp: URLs, the path name given is the absolute name on the
+server. To access a file relative to the remote user's home directory, prefix
+the file with `/~/` , such as:
+
+    curl -u $USER sftp://home.example.com/~/.bashrc
+
+## FTP and Firewalls
+
+The FTP protocol requires one of the involved parties to open a second
+connection as soon as data is about to get transferred. There are two ways to
+do this.
+
+The default way for curl is to issue the PASV command which causes the server
+to open another port and await another connection performed by the
+client. This is good if the client is behind a firewall that doesn't allow
+incoming connections.
+
+    curl ftp.download.com
+
+If the server, for example, is behind a firewall that doesn't allow
+connections on ports other than 21 (or if it just doesn't support the `PASV`
+command), the other way to do it is to use the `PORT` command and instruct the
+server to connect to the client on the given IP number and port (as parameters
+to the PORT command).
+
+The `-P` flag to curl supports a few different options. Your machine may have
+several IP-addresses and/or network interfaces and curl allows you to select
+which of them to use. Default address can also be used:
+
+    curl -P - ftp.download.com
+
+Download with `PORT` but use the IP address of our `le0` interface (this does
+not work on windows):
+
+    curl -P le0 ftp.download.com
+
+Download with `PORT` but use 192.168.0.10 as our IP address to use:
+
+    curl -P 192.168.0.10 ftp.download.com
+
+## Network Interface
+
+Get a web page from a server using a specified port for the interface:
+
+    curl --interface eth0:1 http://www.netscape.com/
+
+or
+
+    curl --interface 192.168.1.10 http://www.netscape.com/
+
+## HTTPS
+
+Secure HTTP requires a TLS library to be installed and used when curl is
+built. If that is done, curl is capable of retrieving and posting documents
+using the HTTPS protocol.
+
+Example:
+
+    curl https://www.secure-site.com
+
+curl is also capable of using client certificates to get/post files from sites
+that require valid certificates. The only drawback is that the certificate
+needs to be in PEM-format. PEM is a standard and open format to store
+certificates with, but it is not used by the most commonly used browsers. If
+you want curl to use the certificates you use with your (favourite) browser,
+you may need to download/compile a converter that can convert your browser's
+formatted certificates to PEM formatted ones.
+
+Example on how to automatically retrieve a document using a certificate with a
+personal password:
+
+    curl -E /path/to/cert.pem:password https://secure.site.com/
+
+If you neglect to specify the password on the command line, you will be
+prompted for the correct password before any data can be received.
+
+Many older HTTPS servers have problems with specific SSL or TLS versions,
+which newer versions of OpenSSL etc use, therefore it is sometimes useful to
+specify what SSL-version curl should use. Use -3, -2 or -1 to specify that
+exact SSL version to use (for SSLv3, SSLv2 or TLSv1 respectively):
+
+    curl -2 https://secure.site.com/
+
+Otherwise, curl will attempt to use a sensible TLS default version.
+
+## Resuming File Transfers
+
+To continue a file transfer where it was previously aborted, curl supports
+esume on HTTP(S) downloads as well as FTP uploads and downloads.
+
+Continue downloading a document:
+
+    curl -C - -o file ftp://ftp.server.com/path/file
+
+Continue uploading a document:
+
+    curl -C - -T file ftp://ftp.server.com/path/file
+
+Continue downloading a document from a web server
+
+    curl -C - -o file http://www.server.com/
+
+## Time Conditions
+
+HTTP allows a client to specify a time condition for the document it requests.
+It is `If-Modified-Since` or `If-Unmodified-Since`. curl allows you to specify
+them with the `-z`/`--time-cond` flag.
+
+For example, you can easily make a download that only gets performed if the
+remote file is newer than a local copy. It would be made like:
+
+    curl -z local.html http://remote.server.com/remote.html
+
+Or you can download a file only if the local file is newer than the remote
+one. Do this by prepending the date string with a `-`, as in:
+
+    curl -z -local.html http://remote.server.com/remote.html
+
+You can specify a "free text" date as condition. Tell curl to only download
+the file if it was updated since January 12, 2012:
+
+    curl -z "Jan 12 2012" http://remote.server.com/remote.html
+
+Curl will then accept a wide range of date formats. You always make the date
+check the other way around by prepending it with a dash (`-`).
+
+## DICT
+
+For fun try
+
+    curl dict://dict.org/m:curl
+    curl dict://dict.org/d:heisenbug:jargon
+    curl dict://dict.org/d:daniel:web1913
+
+Aliases for 'm' are 'match' and 'find', and aliases for 'd' are 'define' and
+'lookup'. For example,
+
+    curl dict://dict.org/find:curl
+
+Commands that break the URL description of the RFC (but not the DICT
+protocol) are
+
+    curl dict://dict.org/show:db
+    curl dict://dict.org/show:strat
+
+Authentication support is still missing
+
+## LDAP
+
+If you have installed the OpenLDAP library, curl can take advantage of it and
+offer `ldap://` support.  On Windows, curl will use WinLDAP from Platform SDK
+by default.
+
+Default protocol version used by curl is LDAPv3. LDAPv2 will be used as
+fallback mechanism in case if LDAPv3 will fail to connect.
+
+LDAP is a complex thing and writing an LDAP query is not an easy task. I do
+advise you to dig up the syntax description for that elsewhere. One such place
+might be: [RFC 2255, The LDAP URL
+Format](https://curl.haxx.se/rfc/rfc2255.txt)
+
+To show you an example, this is how I can get all people from my local LDAP
+server that has a certain sub-domain in their email address:
+
+    curl -B "ldap://ldap.frontec.se/o=frontec??sub?mail=*sth.frontec.se"
+
+If I want the same info in HTML format, I can get it by not using the `-B`
+(enforce ASCII) flag.
+
+You also can use authentication when accessing LDAP catalog:
+
+    curl -u user:passwd "ldap://ldap.frontec.se/o=frontec??sub?mail=*"
+    curl "ldap://user:passwd@ldap.frontec.se/o=frontec??sub?mail=*"
+
+By default, if user and password provided, OpenLDAP/WinLDAP will use basic
+authentication. On Windows you can control this behavior by providing one of
+`--basic`, `--ntlm` or `--digest` option in curl command line
+
+    curl --ntlm "ldap://user:passwd@ldap.frontec.se/o=frontec??sub?mail=*"
+
+On Windows, if no user/password specified, auto-negotiation mechanism will be
+used with current logon credentials (SSPI/SPNEGO).
+
+## Environment Variables
+
+Curl reads and understands the following environment variables:
+
+    http_proxy, HTTPS_PROXY, FTP_PROXY
+
+They should be set for protocol-specific proxies. General proxy should be set
+with
+
+    ALL_PROXY
+
+A comma-separated list of host names that shouldn't go through any proxy is
+set in (only an asterisk, `*` matches all hosts)
+
+    NO_PROXY
+
+If the host name matches one of these strings, or the host is within the
+domain of one of these strings, transactions with that node will not be
+proxied. When a domain is used, it needs to start with a period. A user can
+specify that both www.example.com and foo.example.com should not use a proxy
+by setting `NO_PROXY` to `.example.com`. By including the full name you can
+exclude specific host names, so to make `www.example.com` not use a proxy but
+still have `foo.example.com` do it, set `NO_PROXY` to `www.example.com`.
+
+The usage of the `-x`/`--proxy` flag overrides the environment variables.
+
+## Netrc
+
+Unix introduced the `.netrc` concept a long time ago. It is a way for a user
+to specify name and password for commonly visited FTP sites in a file so that
+you don't have to type them in each time you visit those sites. You realize
+this is a big security risk if someone else gets hold of your passwords, so
+therefore most unix programs won't read this file unless it is only readable
+by yourself (curl doesn't care though).
+
+Curl supports `.netrc` files if told to (using the `-n`/`--netrc` and
+`--netrc-optional` options). This is not restricted to just FTP, so curl can
+use it for all protocols where authentication is used.
+
+A very simple `.netrc` file could look something like:
+
+    machine curl.haxx.se login iamdaniel password mysecret
+
+## Custom Output
+
+To better allow script programmers to get to know about the progress of curl,
+the `-w`/`--write-out` option was introduced. Using this, you can specify what
+information from the previous transfer you want to extract.
+
+To display the amount of bytes downloaded together with some text and an
+ending newline:
+
+    curl -w 'We downloaded %{size_download} bytes\n' www.download.com
+
+## Kerberos FTP Transfer
+
+Curl supports kerberos4 and kerberos5/GSSAPI for FTP transfers. You need the
+kerberos package installed and used at curl build time for it to be available.
+
+First, get the krb-ticket the normal way, like with the kinit/kauth tool.
+Then use curl in way similar to:
+
+    curl --krb private ftp://krb4site.com -u username:fakepwd
+
+There's no use for a password on the `-u` switch, but a blank one will make
+curl ask for one and you already entered the real password to kinit/kauth.
+
+## TELNET
+
+The curl telnet support is basic and very easy to use. Curl passes all data
+passed to it on stdin to the remote server. Connect to a remote telnet server
+using a command line similar to:
+
+    curl telnet://remote.server.com
+
+And enter the data to pass to the server on stdin. The result will be sent to
+stdout or to the file you specify with `-o`.
+
+You might want the `-N`/`--no-buffer` option to switch off the buffered output
+for slow connections or similar.
+
+Pass options to the telnet protocol negotiation, by using the `-t` option. To
+tell the server we use a vt100 terminal, try something like:
+
+    curl -tTTYPE=vt100 telnet://remote.server.com
+
+Other interesting options for it `-t` include:
+
+ - `XDISPLOC=<X display>` Sets the X display location.
+ - `NEW_ENV=<var,val>` Sets an environment variable.
+
+NOTE: The telnet protocol does not specify any way to login with a specified
+user and password so curl can't do that automatically. To do that, you need to
+track when the login prompt is received and send the username and password
+accordingly.
+
+## Persistent Connections
+
+Specifying multiple files on a single command line will make curl transfer all
+of them, one after the other in the specified order.
+
+libcurl will attempt to use persistent connections for the transfers so that
+the second transfer to the same host can use the same connection that was
+already initiated and was left open in the previous transfer. This greatly
+decreases connection time for all but the first transfer and it makes a far
+better use of the network.
+
+Note that curl cannot use persistent connections for transfers that are used
+in subsequence curl invokes. Try to stuff as many URLs as possible on the same
+command line if they are using the same host, as that'll make the transfers
+faster. If you use an HTTP proxy for file transfers, practically all transfers
+will be persistent.
+
+## Multiple Transfers With A Single Command Line
+
+As is mentioned above, you can download multiple files with one command line
+by simply adding more URLs. If you want those to get saved to a local file
+instead of just printed to stdout, you need to add one save option for each
+URL you specify. Note that this also goes for the `-O` option (but not
+`--remote-name-all`).
+
+For example: get two files and use `-O` for the first and a custom file
+name for the second:
+
+    curl -O http://url.com/file.txt ftp://ftp.com/moo.exe -o moo.jpg
+
+You can also upload multiple files in a similar fashion:
+
+    curl -T local1 ftp://ftp.com/moo.exe -T local2 ftp://ftp.com/moo2.txt
+
+## IPv6
+
+curl will connect to a server with IPv6 when a host lookup returns an IPv6
+address and fall back to IPv4 if the connection fails. The `--ipv4` and
+`--ipv6` options can specify which address to use when both are
+available. IPv6 addresses can also be specified directly in URLs using the
+syntax:
+
+    http://[2001:1890:1112:1::20]/overview.html
+
+When this style is used, the `-g` option must be given to stop curl from
+interpreting the square brackets as special globbing characters.  Link local
+and site local addresses including a scope identifier, such as `fe80::1234%1`,
+may also be used, but the scope portion must be numeric or match an existing
+network interface on Linux and the percent character must be URL escaped. The
+previous example in an SFTP URL might look like:
+
+    sftp://[fe80::1234%251]/
+
+IPv6 addresses provided other than in URLs (e.g. to the `--proxy`,
+`--interface` or `--ftp-port` options) should not be URL encoded.
+
+## Metalink
+
+Curl supports Metalink (both version 3 and 4 (RFC 5854) are supported), a way
+to list multiple URIs and hashes for a file. Curl will make use of the mirrors
+listed within for failover if there are errors (such as the file or server not
+being available). It will also verify the hash of the file after the download
+completes. The Metalink file itself is downloaded and processed in memory and
+not stored in the local file system.
+
+Example to use a remote Metalink file:
+
+    curl --metalink http://www.example.com/example.metalink
+
+To use a Metalink file in the local file system, use FILE protocol
+(`file://`):
+
+    curl --metalink file://example.metalink
+
+Please note that if FILE protocol is disabled, there is no way to use a local
+Metalink file at the time of this writing. Also note that if `--metalink` and
+`--include` are used together, `--include` will be ignored. This is because
+including headers in the response will break Metalink parser and if the
+headers are included in the file described in Metalink file, hash check will
+fail.
+
+## Mailing Lists
+
+For your convenience, we have several open mailing lists to discuss curl, its
+development and things relevant to this. Get all info at
+https://curl.haxx.se/mail/.
+
+Please direct curl questions, feature requests and trouble reports to one of
+these mailing lists instead of mailing any individual.
+
+Available lists include:
+
+### curl-users
+
+Users of the command line tool. How to use it, what doesn't work, new
+features, related tools, questions, news, installations, compilations,
+running, porting etc.
+
+### curl-library
+
+Developers using or developing libcurl. Bugs, extensions, improvements.
+
+### curl-announce
+
+Low-traffic. Only receives announcements of new public versions. At worst,
+that makes something like one or two mails per month, but usually only one
+mail every second month.
+
+### curl-and-php
+
+Using the curl functions in PHP. Everything curl with a PHP angle. Or PHP with
+a curl angle.
+
+### curl-and-python
+
+Python hackers using curl with or without the python binding pycurl.
+