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[libcurl.git] / README.curl

LATEST VERSION

  You always find news about what's going on as well as the latest versions
  from the curl web pages, located at:

        http://curl.haxx.nu

SIMPLE USAGE

  Get the main page from netscape's web-server:

        curl http://www.netscape.com/

  Get the root README file from funet's ftp-server:

        curl ftp://ftp.funet.fi/README

  Get a gopher document from funet's gopher server:

        curl gopher://gopher.funet.fi

  Get a web page from a server using port 8000:

        curl http://www.weirdserver.com:8000/

  Get a list of the root directory of an FTP site:

        curl ftp://ftp.fts.frontec.se/

  Get the definition of curl from a dictionary:

        curl dict://dict.org/m:curl

DOWNLOAD TO A FILE

  Get a web page and store in a local file:

        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

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

 HTTP

   The HTTP URL doesn't support user and password in the URL string. Curl
   does support that anyway to provide a ftp-style interface and 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

   NOTE! Since HTTP URLs don't support user and password, you can't use that
   style when using Curl via a proxy. You _must_ use the -u style fetch
   during such circumstances.

 HTTPS

   Probably most commonly used with private certificates, as explained below.

 GOPHER

   Curl features no password support for gopher.

PROXY

 Get an ftp file using a proxy named my-proxy that uses port 888:

        curl -x my-proxy:888 ftp://ftp.leachsite.com/README

 Get a file from a 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/

 See also the environment variables Curl support that offer further proxy
 control.

RANGES

  With HTTP 1.1 byte-ranges were introduced. 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

   Upload all data on stdin to a specified ftp site:

        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 remote
   too:
 
        curl -T uploadfile -u user:passwd ftp://ftp.upload.com/

   NOTE: Curl is not currently supporing ftp upload through a proxy! The reason
   for this is simply that proxies are seldomly configured to allow this and
   that no author has supplied code that makes it possible!

 HTTP

   Upload all data on stdin to a specified http site:

        curl -t http://www.upload.com/myfile

   Note that the http server must've 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 all data it sends and
  receives in order to let the user see all client-server interaction.

        curl -v ftp://ftp.upload.com/

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:

        curl --dump-header headers.txt curl.haxx.nu

  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

  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 which content type the file is, by appending
  ';type=<mime type>' to the file name. You can also post contents of several
  files in one field. So that the field name 'coolfiles' can be sent three
  files with different content types in a manner similar to:

        curl -F "coolfiles=@fil1.gif;type=image/gif,fil2.txt,fil3.html" \
        http://www.post.com/postit.cgi

  If content-type is not specified, curl will try to guess from the 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 finally using the default
  type 'text/plain'.

  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 check out the HTML of the form page to get to
  know 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

  So, to send two files in one post you can do it in two ways:

  1. Send multiple files in a single "field" with a single field name:
 
        curl -F "pictures=@dog.gif,cat.gif" 
 
  2. Send two fields with two field names: 

        curl -F "docpicture=@dog.gif" -F "catpicture=@cat.gif" 

REFERER

  A HTTP request has the option to include information about which address
  that referred to actual page, and curl allows the user to specify that
  referrer to get specified 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

  A 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)'           NS for AIX
    'Mozilla/4.05 [en] (X11; U; Linux 2.0.32 i586)'      NS 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

  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 trig the cookie awareness like:

        curl -L -b empty-file 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.

PROGRESS METER

  The progress meter was introduced to better show a user that something
  actually is happening. The different fields in the output have the following
  meaning:

   %   Received   Total  Speed   Time left  Total   Curr.Speed
  13   524140   3841536   4296   0:12:52   0:14:54    292     

  From left-to-right:
  - The first column, is the percentage of the file currently transfered.
  - Received means the total number of bytes that has been transfered.
  - Total is the total number of bytes expected to transfer.
  - Speed is average speed in bytes per second for the whole transfer so far.
  - Time left is the estimated time left for this transfer to finnish if the
    current average speed will remain steady.
  - Total is the estimated total transfer time.
  - Curr.Speed is the average transfer speed the last 5 seconds (the first
    5 seconds of a transfer is based on less time of course.)

  NOTE: Much of the output is based on the fact that the size of the transfer
  is known before it takes place. If it isn't, a much less fancy display will
  be used.

SPEED LIMIT

  Curl offers the user to set conditions regarding transfer speed 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 doesn't exceed your
  given lowest limit for a specified time.

  To let curl abandon downloading this page if its 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 operatioin must be completed in whole within 30 minutes:

        curl -m 1800 -y 3000 -Y 60 www.far-away-site.com

CONFIG FILE

  Curl automatically tries to read the .curlrc file (or _curlrc file on win32
  systems) from the user's home dir on startup. The config file should be
  made up with normal command line switches. Comments can be used within the
  file. If the first letter on a line is a '#'-letter the rest of the line
  is treated as a comment.

  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:
        -x 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
        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 "-u 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.

FTP and PATH NAMES

  Do note that when getting files with the 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.)

FTP and firewalls

  The FTP protocol requires one of the involved parties to open a second
  connction as soon as data is about to get transfered. 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 don't allow
  incoming connections.

        curl ftp.download.com

  If the server for example, is behind a firewall that don't allow connections
  on other ports 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 (as parameters to the PORT command) IP
  number and port.

  The -P flag to curl allows for 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:

        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

HTTPS

  Secure HTTP requires SSLeay to be installed and used when curl is built. If
  that is done, curl is capable of retrieving and posting documents using the
  HTTPS procotol.

  Example:

        curl https://www.secure-site.com

  Curl is also capable of using your personal 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 (Netscape and MSEI both use the so called PKCS#12 format). 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. Dr Stephen N. Henson has
  written a patch for SSLeay that adds this functionality. You can get his
  patch (that requires an SSLeay installation) from his site at:
  http://www.drh-consultancy.demon.co.uk/

  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 SSL-servers have problems with SSLv3 or TLS, that newer versions
  of OpenSSL etc is using, therefore it is sometimes useful to specify what
  SSL-version curl should use. Use -3 or -2 to specify that exact SSL version
  to use:

        curl -2 https://secure.site.com/

  Otherwise, curl will first attempt to use v3 and then v2.

RESUMING FILE TRANSFERS

 To continue a file transfer where it was previously aborted, curl supports
 resume 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(*1):

        curl -c -T file ftp://ftp.server.com/path/file

 Continue downloading a document from a web server(*2):

        curl -c -o file http://www.server.com/

 (*1) = This requires that the ftp server supports the non-standard command
        SIZE. If it doesn't, curl will say so.

 (*2) = This requires that the wb server supports at least HTTP/1.1. If it
        doesn't, curl will say so.

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 allow 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 yesterday:

        curl -z yesterday 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 is still missing (but this is not required by the RFC)

LDAP

  If you have installed the OpenLDAP library, curl can take advantage of it
  and offer ldap:// support.

  LDAP is a complex thing and writing an LDAP query is not an easy task. I do
  advice you to dig up the syntax description for that elsewhere, RFC 1959 if
  no other place is better.

  To show you an example, this is now 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.

ENVIRONMENT VARIABLES

  Curl reads and understands the following environment variables:

        HTTP_PROXY, HTTPS_PROXY, FTP_PROXY, GOPHER_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 a tail substring of the domain-path for a host matches one of these
  strings, transactions with that node will not be proxied.


  The usage of the -x/--proxy flag overrides the environment variables.

MAILING LIST

  We have an open mailing list to discuss curl, its development and things
  relevant to this.

  To subscribe, mail curl-request@contactor.se with "subscribe <your email
  address>" in the body.

  To post to the list, mail curl@contactor.se.

  To unsubcribe, mail curl-request@contactor.se with "unsubscribe <your
  subscribed email address>" in the body.