Updated cURL version.
This commit is contained in:
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Online: http://curl.haxx.se/docs/httpscripting.html
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Date: May 28, 2008
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Date: Jan 19, 2011
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The Art Of Scripting HTTP Requests Using Curl
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=============================================
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@@ -38,10 +38,26 @@ Date: May 28, 2008
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request a particular action, and then the server replies a few text lines
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before the actual requested content is sent to the client.
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Using curl's option -v will display what kind of commands curl sends to the
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server, as well as a few other informational texts. -v is the single most
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useful option when it comes to debug or even understand the curl<->server
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interaction.
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The client, curl, sends a HTTP request. The request contains a method (like
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GET, POST, HEAD etc), a number of request headers and sometimes a request
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body. The HTTP server responds with a status line (indicating if things went
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well), response headers and most often also a response body. The "body" part
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is the plain data you requested, like the actual HTML or the image etc.
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1.1 See the Protocol
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Using curl's option --verbose (-v as a short option) will display what kind
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of commands curl sends to the server, as well as a few other informational
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texts.
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--verbose is the single most useful option when it comes to debug or even
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understand the curl<->server interaction.
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Sometimes even --verbose is not enough. Then --trace and --trace-ascii offer
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even more details as they show EVERYTHING curl sends and receives. Use it
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like this:
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curl --trace-ascii debugdump.txt http://www.example.com/
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2. URL
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@@ -61,10 +77,10 @@ Date: May 28, 2008
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you get a web page returned in your terminal window. The entire HTML document
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that that URL holds.
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All HTTP replies contain a set of headers that are normally hidden, use
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curl's -i option to display them as well as the rest of the document. You can
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also ask the remote server for ONLY the headers by using the -I option (which
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will make curl issue a HEAD request).
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All HTTP replies contain a set of response headers that are normally hidden,
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use curl's --include (-i) option to display them as well as the rest of the
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document. You can also ask the remote server for ONLY the headers by using
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the --head (-I) option (which will make curl issue a HEAD request).
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4. Forms
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@@ -103,7 +119,7 @@ Date: May 28, 2008
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To make curl do the GET form post for you, just enter the expected created
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URL:
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curl "www.hotmail.com/when/junk.cgi?birthyear=1905&press=OK"
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curl "http://www.hotmail.com/when/junk.cgi?birthyear=1905&press=OK"
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4.2 POST
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@@ -127,7 +143,8 @@ Date: May 28, 2008
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And to use curl to post this form with the same data filled in as before, we
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could do it like:
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curl -d "birthyear=1905&press=%20OK%20" www.hotmail.com/when/junk.cgi
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curl --data "birthyear=1905&press=%20OK%20" \
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http://www.example.com/when.cgi
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This kind of POST will use the Content-Type
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application/x-www-form-urlencoded and is the most widely used POST kind.
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@@ -139,7 +156,7 @@ Date: May 28, 2008
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Recent curl versions can in fact url-encode POST data for you, like this:
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curl --data-urlencode "name=I am Daniel" www.example.com
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curl --data-urlencode "name=I am Daniel" http://www.example.com
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4.3 File Upload POST
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@@ -160,7 +177,7 @@ Date: May 28, 2008
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To post to a form like this with curl, you enter a command line like:
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curl -F upload=@localfilename -F press=OK [URL]
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curl --form upload=@localfilename --form press=OK [URL]
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4.4 Hidden Fields
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@@ -181,7 +198,7 @@ Date: May 28, 2008
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To post this with curl, you won't have to think about if the fields are
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hidden or not. To curl they're all the same:
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curl -d "birthyear=1905&press=OK&person=daniel" [URL]
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curl --data "birthyear=1905&press=OK&person=daniel" [URL]
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4.5 Figure Out What A POST Looks Like
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@@ -204,7 +221,7 @@ Date: May 28, 2008
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Put a file to a HTTP server with curl:
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curl -T uploadfile www.uploadhttp.com/receive.cgi
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curl --upload-file uploadfile http://www.example.com/receive.cgi
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6. HTTP Authentication
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@@ -217,18 +234,18 @@ Date: May 28, 2008
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To tell curl to use a user and password for authentication:
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curl -u name:password www.secrets.com
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curl --user name:password http://www.example.com
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The site might require a different authentication method (check the headers
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returned by the server), and then --ntlm, --digest, --negotiate or even
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--anyauth might be options that suit you.
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Sometimes your HTTP access is only available through the use of a HTTP
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proxy. This seems to be especially common at various companies. A HTTP proxy
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may require its own user and password to allow the client to get through to
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the Internet. To specify those with curl, run something like:
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curl -U proxyuser:proxypassword curl.haxx.se
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curl --proxy-user proxyuser:proxypassword curl.haxx.se
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If your proxy requires the authentication to be done using the NTLM method,
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use --proxy-ntlm, if it requires Digest use --proxy-digest.
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@@ -257,7 +274,7 @@ Date: May 28, 2008
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Use curl to set the referer field with:
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curl -e http://curl.haxx.se daniel.haxx.se
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curl --referer http://www.example.come http://www.example.com
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8. User Agent
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@@ -273,13 +290,13 @@ Date: May 28, 2008
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is time to set the User Agent field to fool the server into thinking you're
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one of those browsers.
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To make curl look like Internet Explorer on a Windows 2000 box:
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To make curl look like Internet Explorer 5 on a Windows 2000 box:
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curl -A "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)" [URL]
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curl --user-agent "Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)" [URL]
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Or why not look like you're using Netscape 4.73 on a Linux (PIII) box:
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Or why not look like you're using Netscape 4.73 on an old Linux box:
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curl -A "Mozilla/4.73 [en] (X11; U; Linux 2.2.15 i686)" [URL]
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curl --user-agent "Mozilla/4.73 [en] (X11; U; Linux 2.2.15 i686)" [URL]
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9. Redirects
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@@ -292,13 +309,14 @@ Date: May 28, 2008
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such pages in the same manner it display all HTTP replies. It does however
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feature an option that will make it attempt to follow the Location: pointers.
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To tell curl to follow a Location:
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curl -L www.sitethatredirects.com
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To tell curl to follow a Location:
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curl --location http://www.example.com
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If you use curl to POST to a site that immediately redirects you to another
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page, you can safely use -L and -d/-F together. Curl will only use POST in
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the first request, and then revert to GET in the following operations.
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page, you can safely use --location (-L) and --data/--form together. Curl will
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only use POST in the first request, and then revert to GET in the following
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operations.
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10. Cookies
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@@ -320,16 +338,16 @@ Date: May 28, 2008
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The simplest way to send a few cookies to the server when getting a page with
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curl is to add them on the command line like:
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curl -b "name=Daniel" www.cookiesite.com
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curl --cookie "name=Daniel" http://www.example.com
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Cookies are sent as common HTTP headers. This is practical as it allows curl
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to record cookies simply by recording headers. Record cookies with curl by
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using the -D option like:
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using the --dump-header (-D) option like:
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curl -D headers_and_cookies www.cookiesite.com
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curl --dump-header headers_and_cookies http://www.example.com
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(Take note that the -c option described below is a better way to store
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cookies.)
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(Take note that the --cookie-jar option described below is a better way to
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store cookies.)
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Curl has a full blown cookie parsing engine built-in that comes to use if you
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want to reconnect to a server and use cookies that were stored from a
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@@ -337,24 +355,25 @@ Date: May 28, 2008
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believing you had a previous connection). To use previously stored cookies,
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you run curl like:
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curl -b stored_cookies_in_file www.cookiesite.com
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curl --cookie stored_cookies_in_file http://www.example.com
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Curl's "cookie engine" gets enabled when you use the -b option. If you only
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want curl to understand received cookies, use -b with a file that doesn't
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exist. Example, if you want to let curl understand cookies from a page and
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follow a location (and thus possibly send back cookies it received), you can
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invoke it like:
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Curl's "cookie engine" gets enabled when you use the --cookie option. If you
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only want curl to understand received cookies, use --cookie with a file that
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doesn't exist. Example, if you want to let curl understand cookies from a
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page and follow a location (and thus possibly send back cookies it received),
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you can invoke it like:
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curl -b nada -L www.cookiesite.com
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curl --cookie nada --location http://www.example.com
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Curl has the ability to read and write cookie files that use the same file
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format that Netscape and Mozilla do. It is a convenient way to share cookies
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between browsers and automatic scripts. The -b switch automatically detects
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if a given file is such a cookie file and parses it, and by using the
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-c/--cookie-jar option you'll make curl write a new cookie file at the end of
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an operation:
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between browsers and automatic scripts. The --cookie (-b) switch
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automatically detects if a given file is such a cookie file and parses it,
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and by using the --cookie-jar (-c) option you'll make curl write a new cookie
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file at the end of an operation:
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curl -b cookies.txt -c newcookies.txt www.cookiesite.com
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curl --cookie cookies.txt --cookie-jar newcookies.txt \
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http://www.example.com
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11. HTTPS
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@@ -370,7 +389,7 @@ Date: May 28, 2008
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Curl supports encrypted fetches thanks to the freely available OpenSSL
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libraries. To get a page from a HTTPS server, simply run curl like:
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curl https://that.secure.server.com
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curl https://secure.example.com
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11.1 Certificates
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@@ -381,13 +400,13 @@ Date: May 28, 2008
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can be specified on the command line or if not, entered interactively when
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curl queries for it. Use a certificate with curl on a HTTPS server like:
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curl -E mycert.pem https://that.secure.server.com
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curl --cert mycert.pem https://secure.example.com
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curl also tries to verify that the server is who it claims to be, by
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verifying the server's certificate against a locally stored CA cert
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bundle. Failing the verification will cause curl to deny the connection. You
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must then use -k in case you want to tell curl to ignore that the server
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can't be verified.
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must then use --insecure (-k) in case you want to tell curl to ignore that
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the server can't be verified.
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More about server certificate verification and ca cert bundles can be read
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in the SSLCERTS document, available online here:
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@@ -402,17 +421,18 @@ Date: May 28, 2008
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For example, you can change the POST request to a PROPFIND and send the data
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as "Content-Type: text/xml" (instead of the default Content-Type) like this:
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curl -d "<xml>" -H "Content-Type: text/xml" -X PROPFIND url.com
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curl --data "<xml>" --header "Content-Type: text/xml" \
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--request PROPFIND url.com
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You can delete a default header by providing one without content. Like you
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can ruin the request by chopping off the Host: header:
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curl -H "Host:" http://mysite.com
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curl --header "Host:" http://www.example.com
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You can add headers the same way. Your server may want a "Destination:"
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header, and you can add it:
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curl -H "Destination: http://moo.com/nowhere" http://url.com
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curl --header "Destination: http://nowhere" http://example.com
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13. Web Login
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@@ -443,7 +463,6 @@ Date: May 28, 2008
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to do a proper login POST. Remember that the contents need to be URL encoded
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when sent in a normal POST.
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14. Debug
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Many times when you run curl on a site, you'll notice that the site doesn't
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@@ -456,8 +475,8 @@ Date: May 28, 2008
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* Use the --trace-ascii option to store fully detailed logs of the requests
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for easier analyzing and better understanding
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* Make sure you check for and use cookies when needed (both reading with -b
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and writing with -c)
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* Make sure you check for and use cookies when needed (both reading with
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--cookie and writing with --cookie-jar)
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* Set user-agent to one like a recent popular browser does
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@@ -479,12 +498,10 @@ Date: May 28, 2008
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RFC 2616 is a must to read if you want in-depth understanding of the HTTP
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protocol.
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RFC 2396 explains the URL syntax.
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RFC 3986 explains the URL syntax.
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RFC 2109 defines how cookies are supposed to work.
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RFC 1867 defines the HTTP post upload format.
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http://www.openssl.org is the home of the OpenSSL project
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http://curl.haxx.se is the home of the cURL project
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