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1LATEST VERSION
2
3  You always find news about what's going on as well as the latest versions
4  from the curl web pages, located at:
5
6        https://curl.haxx.se
7
8SIMPLE USAGE
9
10  Get the main page from Netscape's web-server:
11
12        curl http://www.netscape.com/
13
14  Get the README file the user's home directory at funet's ftp-server:
15
16        curl ftp://ftp.funet.fi/README
17
18  Get a web page from a server using port 8000:
19
20        curl http://www.weirdserver.com:8000/
21
22  Get a directory listing of an FTP site:
23
24        curl ftp://cool.haxx.se/
25
26  Get the definition of curl from a dictionary:
27
28        curl dict://dict.org/m:curl
29
30  Fetch two documents at once:
31
32        curl ftp://cool.haxx.se/ http://www.weirdserver.com:8000/
33
34  Get a file off an FTPS server:
35
36        curl ftps://files.are.secure.com/secrets.txt
37
38  or use the more appropriate FTPS way to get the same file:
39
40        curl --ftp-ssl ftp://files.are.secure.com/secrets.txt
41
42  Get a file from an SSH server using SFTP:
43
44        curl -u username sftp://example.com/etc/issue
45
46  Get a file from an SSH server using SCP using a private key
47  (not password-protected) to authenticate:
48
49        curl -u username: --key ~/.ssh/id_rsa \
50             scp://example.com/~/file.txt
51
52  Get a file from an SSH server using SCP using a private key
53  (password-protected) to authenticate:
54
55        curl -u username: --key ~/.ssh/id_rsa --pass private_key_password \
56             scp://example.com/~/file.txt
57
58  Get the main page from an IPv6 web server:
59
60        curl "http://[2001:1890:1112:1::20]/"
61
62  Get a file from an SMB server:
63
64        curl -u "domain\username:passwd" smb://server.example.com/share/file.txt
65
66DOWNLOAD TO A FILE
67
68  Get a web page and store in a local file with a specific name:
69
70        curl -o thatpage.html http://www.netscape.com/
71
72  Get a web page and store in a local file, make the local file get the name
73  of the remote document (if no file name part is specified in the URL, this
74  will fail):
75
76        curl -O http://www.netscape.com/index.html
77
78  Fetch two files and store them with their remote names:
79
80        curl -O www.haxx.se/index.html -O curl.haxx.se/download.html
81
82USING PASSWORDS
83
84 FTP
85
86   To ftp files using name+passwd, include them in the URL like:
87
88        curl ftp://name:passwd@machine.domain:port/full/path/to/file
89
90   or specify them with the -u flag like
91
92        curl -u name:passwd ftp://machine.domain:port/full/path/to/file
93
94 FTPS
95
96   It is just like for FTP, but you may also want to specify and use
97   SSL-specific options for certificates etc.
98
99   Note that using FTPS:// as prefix is the "implicit" way as described in the
100   standards while the recommended "explicit" way is done by using FTP:// and
101   the --ftp-ssl option.
102
103 SFTP / SCP
104
105   This is similar to FTP, but you can use the --key option to specify a
106   private key to use instead of a password. Note that the private key may
107   itself be protected by a password that is unrelated to the login password
108   of the remote system; this password is specified using the --pass option.
109   Typically, curl will automatically extract the public key from the private
110   key file, but in cases where curl does not have the proper library support,
111   a matching public key file must be specified using the --pubkey option.
112
113 HTTP
114
115   Curl also supports user and password in HTTP URLs, thus you can pick a file
116   like:
117
118        curl http://name:passwd@machine.domain/full/path/to/file
119
120   or specify user and password separately like in
121
122        curl -u name:passwd http://machine.domain/full/path/to/file
123
124   HTTP offers many different methods of authentication and curl supports
125   several: Basic, Digest, NTLM and Negotiate (SPNEGO). Without telling which
126   method to use, curl defaults to Basic. You can also ask curl to pick the
127   most secure ones out of the ones that the server accepts for the given URL,
128   by using --anyauth.
129
130   NOTE! According to the URL specification, HTTP URLs can not contain a user
131   and password, so that style will not work when using curl via a proxy, even
132   though curl allows it at other times. When using a proxy, you _must_ use
133   the -u style for user and password.
134
135 HTTPS
136
137   Probably most commonly used with private certificates, as explained below.
138
139PROXY
140
141 curl supports both HTTP and SOCKS proxy servers, with optional authentication.
142 It does not have special support for FTP proxy servers since there are no
143 standards for those, but it can still be made to work with many of them. You
144 can also use both HTTP and SOCKS proxies to transfer files to and from FTP
145 servers.
146
147 Get an ftp file using an HTTP proxy named my-proxy that uses port 888:
148
149        curl -x my-proxy:888 ftp://ftp.leachsite.com/README
150
151 Get a file from an HTTP server that requires user and password, using the
152 same proxy as above:
153
154        curl -u user:passwd -x my-proxy:888 http://www.get.this/
155
156 Some proxies require special authentication. Specify by using -U as above:
157
158        curl -U user:passwd -x my-proxy:888 http://www.get.this/
159
160 A comma-separated list of hosts and domains which do not use the proxy can
161 be specified as:
162
163        curl --noproxy localhost,get.this -x my-proxy:888 http://www.get.this/
164
165 If the proxy is specified with --proxy1.0 instead of --proxy or -x, then
166 curl will use HTTP/1.0 instead of HTTP/1.1 for any CONNECT attempts.
167
168 curl also supports SOCKS4 and SOCKS5 proxies with --socks4 and --socks5.
169
170 See also the environment variables Curl supports that offer further proxy
171 control.
172
173 Most FTP proxy servers are set up to appear as a normal FTP server from the
174 client's perspective, with special commands to select the remote FTP server.
175 curl supports the -u, -Q and --ftp-account options that can be used to
176 set up transfers through many FTP proxies. For example, a file can be
177 uploaded to a remote FTP server using a Blue Coat FTP proxy with the
178 options:
179
180   curl -u "Remote-FTP-Username@remote.ftp.server Proxy-Username:Remote-Pass" \
181    --ftp-account Proxy-Password --upload-file local-file \
182    ftp://my-ftp.proxy.server:21/remote/upload/path/
183
184 See the manual for your FTP proxy to determine the form it expects to set up
185 transfers, and curl's -v option to see exactly what curl is sending.
186
187RANGES
188
189  HTTP 1.1 introduced byte-ranges. Using this, a client can request
190  to get only one or more subparts of a specified document. Curl supports
191  this with the -r flag.
192
193  Get the first 100 bytes of a document:
194
195        curl -r 0-99 http://www.get.this/
196
197  Get the last 500 bytes of a document:
198
199        curl -r -500 http://www.get.this/
200
201  Curl also supports simple ranges for FTP files as well. Then you can only
202  specify start and stop position.
203
204  Get the first 100 bytes of a document using FTP:
205
206        curl -r 0-99 ftp://www.get.this/README
207
208UPLOADING
209
210 FTP / FTPS / SFTP / SCP
211
212  Upload all data on stdin to a specified server:
213
214        curl -T - ftp://ftp.upload.com/myfile
215
216  Upload data from a specified file, login with user and password:
217
218        curl -T uploadfile -u user:passwd ftp://ftp.upload.com/myfile
219
220  Upload a local file to the remote site, and use the local file name at the remote
221  site too:
222
223        curl -T uploadfile -u user:passwd ftp://ftp.upload.com/
224
225  Upload a local file to get appended to the remote file:
226
227        curl -T localfile -a ftp://ftp.upload.com/remotefile
228
229  Curl also supports ftp upload through a proxy, but only if the proxy is
230  configured to allow that kind of tunneling. If it does, you can run curl in
231  a fashion similar to:
232
233        curl --proxytunnel -x proxy:port -T localfile ftp.upload.com
234
235SMB / SMBS
236
237        curl -T file.txt -u "domain\username:passwd"
238         smb://server.example.com/share/
239
240 HTTP
241
242  Upload all data on stdin to a specified HTTP site:
243
244        curl -T - http://www.upload.com/myfile
245
246  Note that the HTTP server must have been configured to accept PUT before
247  this can be done successfully.
248
249  For other ways to do HTTP data upload, see the POST section below.
250
251VERBOSE / DEBUG
252
253  If curl fails where it isn't supposed to, if the servers don't let you in,
254  if you can't understand the responses: use the -v flag to get verbose
255  fetching. Curl will output lots of info and what it sends and receives in
256  order to let the user see all client-server interaction (but it won't show
257  you the actual data).
258
259        curl -v ftp://ftp.upload.com/
260
261  To get even more details and information on what curl does, try using the
262  --trace or --trace-ascii options with a given file name to log to, like
263  this:
264
265        curl --trace trace.txt www.haxx.se
266
267
268DETAILED INFORMATION
269
270  Different protocols provide different ways of getting detailed information
271  about specific files/documents. To get curl to show detailed information
272  about a single file, you should use -I/--head option. It displays all
273  available info on a single file for HTTP and FTP. The HTTP information is a
274  lot more extensive.
275
276  For HTTP, you can get the header information (the same as -I would show)
277  shown before the data by using -i/--include. Curl understands the
278  -D/--dump-header option when getting files from both FTP and HTTP, and it
279  will then store the headers in the specified file.
280
281  Store the HTTP headers in a separate file (headers.txt in the example):
282
283        curl --dump-header headers.txt curl.haxx.se
284
285  Note that headers stored in a separate file can be very useful at a later
286  time if you want curl to use cookies sent by the server. More about that in
287  the cookies section.
288
289POST (HTTP)
290
291  It's easy to post data using curl. This is done using the -d <data>
292  option.  The post data must be urlencoded.
293
294  Post a simple "name" and "phone" guestbook.
295
296        curl -d "name=Rafael%20Sagula&phone=3320780" \
297                http://www.where.com/guest.cgi
298
299  How to post a form with curl, lesson #1:
300
301  Dig out all the <input> tags in the form that you want to fill in. (There's
302  a perl program called formfind.pl on the curl site that helps with this).
303
304  If there's a "normal" post, you use -d to post. -d takes a full "post
305  string", which is in the format
306
307        <variable1>=<data1>&<variable2>=<data2>&...
308
309  The 'variable' names are the names set with "name=" in the <input> tags, and
310  the data is the contents you want to fill in for the inputs. The data *must*
311  be properly URL encoded. That means you replace space with + and that you
312  replace weird letters with %XX where XX is the hexadecimal representation of
313  the letter's ASCII code.
314
315  Example:
316
317  (page located at http://www.formpost.com/getthis/
318
319        <form action="post.cgi" method="post">
320        <input name=user size=10>
321        <input name=pass type=password size=10>
322        <input name=id type=hidden value="blablabla">
323        <input name=ding value="submit">
324        </form>
325
326  We want to enter user 'foobar' with password '12345'.
327
328  To post to this, you enter a curl command line like:
329
330        curl -d "user=foobar&pass=12345&id=blablabla&ding=submit"  (continues)
331          http://www.formpost.com/getthis/post.cgi
332
333
334  While -d uses the application/x-www-form-urlencoded mime-type, generally
335  understood by CGI's and similar, curl also supports the more capable
336  multipart/form-data type. This latter type supports things like file upload.
337
338  -F accepts parameters like -F "name=contents". If you want the contents to
339  be read from a file, use <@filename> as contents. When specifying a file,
340  you can also specify the file content type by appending ';type=<mime type>'
341  to the file name. You can also post the contents of several files in one
342  field.  For example, the field name 'coolfiles' is used to send three files,
343  with different content types using the following syntax:
344
345        curl -F "coolfiles=@fil1.gif;type=image/gif,fil2.txt,fil3.html" \
346        http://www.post.com/postit.cgi
347
348  If the content-type is not specified, curl will try to guess from the file
349  extension (it only knows a few), or use the previously specified type (from
350  an earlier file if several files are specified in a list) or else it will
351  use the default type 'application/octet-stream'.
352
353  Emulate a fill-in form with -F. Let's say you fill in three fields in a
354  form. One field is a file name which to post, one field is your name and one
355  field is a file description. We want to post the file we have written named
356  "cooltext.txt". To let curl do the posting of this data instead of your
357  favourite browser, you have to read the HTML source of the form page and
358  find the names of the input fields. In our example, the input field names
359  are 'file', 'yourname' and 'filedescription'.
360
361        curl -F "file=@cooltext.txt" -F "yourname=Daniel" \
362             -F "filedescription=Cool text file with cool text inside" \
363             http://www.post.com/postit.cgi
364
365  To send two files in one post you can do it in two ways:
366
367  1. Send multiple files in a single "field" with a single field name:
368
369        curl -F "pictures=@dog.gif,cat.gif"
370
371  2. Send two fields with two field names:
372
373        curl -F "docpicture=@dog.gif" -F "catpicture=@cat.gif"
374
375  To send a field value literally without interpreting a leading '@'
376  or '<', or an embedded ';type=', use --form-string instead of
377  -F. This is recommended when the value is obtained from a user or
378  some other unpredictable source. Under these circumstances, using
379  -F instead of --form-string would allow a user to trick curl into
380  uploading a file.
381
382REFERRER
383
384  An HTTP request has the option to include information about which address
385  referred it to the actual page.  Curl allows you to specify the
386  referrer to be used on the command line. It is especially useful to
387  fool or trick stupid servers or CGI scripts that rely on that information
388  being available or contain certain data.
389
390        curl -e www.coolsite.com http://www.showme.com/
391
392  NOTE: The Referer: [sic] field is defined in the HTTP spec to be a full URL.
393
394USER AGENT
395
396  An HTTP request has the option to include information about the browser
397  that generated the request. Curl allows it to be specified on the command
398  line. It is especially useful to fool or trick stupid servers or CGI
399  scripts that only accept certain browsers.
400
401  Example:
402
403  curl -A 'Mozilla/3.0 (Win95; I)' http://www.nationsbank.com/
404
405  Other common strings:
406    'Mozilla/3.0 (Win95; I)'     Netscape Version 3 for Windows 95
407    'Mozilla/3.04 (Win95; U)'    Netscape Version 3 for Windows 95
408    'Mozilla/2.02 (OS/2; U)'     Netscape Version 2 for OS/2
409    'Mozilla/4.04 [en] (X11; U; AIX 4.2; Nav)'           NS for AIX
410    'Mozilla/4.05 [en] (X11; U; Linux 2.0.32 i586)'      NS for Linux
411
412  Note that Internet Explorer tries hard to be compatible in every way:
413    'Mozilla/4.0 (compatible; MSIE 4.01; Windows 95)'    MSIE for W95
414
415  Mozilla is not the only possible User-Agent name:
416    'Konqueror/1.0'             KDE File Manager desktop client
417    'Lynx/2.7.1 libwww-FM/2.14' Lynx command line browser
418
419COOKIES
420
421  Cookies are generally used by web servers to keep state information at the
422  client's side. The server sets cookies by sending a response line in the
423  headers that looks like 'Set-Cookie: <data>' where the data part then
424  typically contains a set of NAME=VALUE pairs (separated by semicolons ';'
425  like "NAME1=VALUE1; NAME2=VALUE2;"). The server can also specify for what
426  path the "cookie" should be used for (by specifying "path=value"), when the
427  cookie should expire ("expire=DATE"), for what domain to use it
428  ("domain=NAME") and if it should be used on secure connections only
429  ("secure").
430
431  If you've received a page from a server that contains a header like:
432        Set-Cookie: sessionid=boo123; path="/foo";
433
434  it means the server wants that first pair passed on when we get anything in
435  a path beginning with "/foo".
436
437  Example, get a page that wants my name passed in a cookie:
438
439        curl -b "name=Daniel" www.sillypage.com
440
441  Curl also has the ability to use previously received cookies in following
442  sessions. If you get cookies from a server and store them in a file in a
443  manner similar to:
444
445        curl --dump-header headers www.example.com
446
447  ... you can then in a second connect to that (or another) site, use the
448  cookies from the 'headers' file like:
449
450        curl -b headers www.example.com
451
452  While saving headers to a file is a working way to store cookies, it is
453  however error-prone and not the preferred way to do this. Instead, make curl
454  save the incoming cookies using the well-known netscape cookie format like
455  this:
456
457        curl -c cookies.txt www.example.com
458
459  Note that by specifying -b you enable the "cookie awareness" and with -L
460  you can make curl follow a location: (which often is used in combination
461  with cookies). So that if a site sends cookies and a location, you can
462  use a non-existing file to trigger the cookie awareness like:
463
464        curl -L -b empty.txt www.example.com
465
466  The file to read cookies from must be formatted using plain HTTP headers OR
467  as netscape's cookie file. Curl will determine what kind it is based on the
468  file contents.  In the above command, curl will parse the header and store
469  the cookies received from www.example.com.  curl will send to the server the
470  stored cookies which match the request as it follows the location.  The
471  file "empty.txt" may be a nonexistent file.
472
473  To read and write cookies from a netscape cookie file, you can set both -b
474  and -c to use the same file:
475
476        curl -b cookies.txt -c cookies.txt www.example.com
477
478PROGRESS METER
479
480  The progress meter exists to show a user that something actually is
481  happening. The different fields in the output have the following meaning:
482
483  % Total    % Received % Xferd  Average Speed          Time             Curr.
484                                 Dload  Upload Total    Current  Left    Speed
485  0  151M    0 38608    0     0   9406      0  4:41:43  0:00:04  4:41:39  9287
486
487  From left-to-right:
488   %             - percentage completed of the whole transfer
489   Total         - total size of the whole expected transfer
490   %             - percentage completed of the download
491   Received      - currently downloaded amount of bytes
492   %             - percentage completed of the upload
493   Xferd         - currently uploaded amount of bytes
494   Average Speed
495   Dload         - the average transfer speed of the download
496   Average Speed
497   Upload        - the average transfer speed of the upload
498   Time Total    - expected time to complete the operation
499   Time Current  - time passed since the invoke
500   Time Left     - expected time left to completion
501   Curr.Speed    - the average transfer speed the last 5 seconds (the first
502                   5 seconds of a transfer is based on less time of course.)
503
504  The -# option will display a totally different progress bar that doesn't
505  need much explanation!
506
507SPEED LIMIT
508
509  Curl allows the user to set the transfer speed conditions that must be met
510  to let the transfer keep going. By using the switch -y and -Y you
511  can make curl abort transfers if the transfer speed is below the specified
512  lowest limit for a specified time.
513
514  To have curl abort the download if the speed is slower than 3000 bytes per
515  second for 1 minute, run:
516
517        curl -Y 3000 -y 60 www.far-away-site.com
518
519  This can very well be used in combination with the overall time limit, so
520  that the above operation must be completed in whole within 30 minutes:
521
522        curl -m 1800 -Y 3000 -y 60 www.far-away-site.com
523
524  Forcing curl not to transfer data faster than a given rate is also possible,
525  which might be useful if you're using a limited bandwidth connection and you
526  don't want your transfer to use all of it (sometimes referred to as
527  "bandwidth throttle").
528
529  Make curl transfer data no faster than 10 kilobytes per second:
530
531        curl --limit-rate 10K www.far-away-site.com
532
533    or
534
535        curl --limit-rate 10240 www.far-away-site.com
536
537  Or prevent curl from uploading data faster than 1 megabyte per second:
538
539        curl -T upload --limit-rate 1M ftp://uploadshereplease.com
540
541  When using the --limit-rate option, the transfer rate is regulated on a
542  per-second basis, which will cause the total transfer speed to become lower
543  than the given number. Sometimes of course substantially lower, if your
544  transfer stalls during periods.
545
546CONFIG FILE
547
548  Curl automatically tries to read the .curlrc file (or _curlrc file on win32
549  systems) from the user's home dir on startup.
550
551  The config file could be made up with normal command line switches, but you
552  can also specify the long options without the dashes to make it more
553  readable. You can separate the options and the parameter with spaces, or
554  with = or :. Comments can be used within the file. If the first letter on a
555  line is a '#'-symbol the rest of the line is treated as a comment.
556
557  If you want the parameter to contain spaces, you must enclose the entire
558  parameter within double quotes ("). Within those quotes, you specify a
559  quote as \".
560
561  NOTE: You must specify options and their arguments on the same line.
562
563  Example, set default time out and proxy in a config file:
564
565        # We want a 30 minute timeout:
566        -m 1800
567        # ... and we use a proxy for all accesses:
568        proxy = proxy.our.domain.com:8080
569
570  White spaces ARE significant at the end of lines, but all white spaces
571  leading up to the first characters of each line are ignored.
572
573  Prevent curl from reading the default file by using -q as the first command
574  line parameter, like:
575
576        curl -q www.thatsite.com
577
578  Force curl to get and display a local help page in case it is invoked
579  without URL by making a config file similar to:
580
581        # default url to get
582        url = "http://help.with.curl.com/curlhelp.html"
583
584  You can specify another config file to be read by using the -K/--config
585  flag. If you set config file name to "-" it'll read the config from stdin,
586  which can be handy if you want to hide options from being visible in process
587  tables etc:
588
589        echo "user = user:passwd" | curl -K - http://that.secret.site.com
590
591EXTRA HEADERS
592
593  When using curl in your own very special programs, you may end up needing
594  to pass on your own custom headers when getting a web page. You can do
595  this by using the -H flag.
596
597  Example, send the header "X-you-and-me: yes" to the server when getting a
598  page:
599
600        curl -H "X-you-and-me: yes" www.love.com
601
602  This can also be useful in case you want curl to send a different text in a
603  header than it normally does. The -H header you specify then replaces the
604  header curl would normally send. If you replace an internal header with an
605  empty one, you prevent that header from being sent. To prevent the Host:
606  header from being used:
607
608        curl -H "Host:" www.server.com
609
610FTP and PATH NAMES
611
612  Do note that when getting files with the ftp:// URL, the given path is
613  relative the directory you enter. To get the file 'README' from your home
614  directory at your ftp site, do:
615
616        curl ftp://user:passwd@my.site.com/README
617
618  But if you want the README file from the root directory of that very same
619  site, you need to specify the absolute file name:
620
621        curl ftp://user:passwd@my.site.com//README
622
623  (I.e with an extra slash in front of the file name.)
624
625SFTP and SCP and PATH NAMES
626
627  With sftp: and scp: URLs, the path name given is the absolute name on the
628  server. To access a file relative to the remote user's home directory,
629  prefix the file with /~/ , such as:
630
631        curl -u $USER sftp://home.example.com/~/.bashrc
632
633FTP and firewalls
634
635  The FTP protocol requires one of the involved parties to open a second
636  connection as soon as data is about to get transferred. There are two ways to
637  do this.
638
639  The default way for curl is to issue the PASV command which causes the
640  server to open another port and await another connection performed by the
641  client. This is good if the client is behind a firewall that doesn't allow
642  incoming connections.
643
644        curl ftp.download.com
645
646  If the server, for example, is behind a firewall that doesn't allow connections
647  on ports other than 21 (or if it just doesn't support the PASV command), the
648  other way to do it is to use the PORT command and instruct the server to
649  connect to the client on the given IP number and port (as parameters to the
650  PORT command).
651
652  The -P flag to curl supports a few different options. Your machine may have
653  several IP-addresses and/or network interfaces and curl allows you to select
654  which of them to use. Default address can also be used:
655
656        curl -P - ftp.download.com
657
658  Download with PORT but use the IP address of our 'le0' interface (this does
659  not work on windows):
660
661        curl -P le0 ftp.download.com
662
663  Download with PORT but use 192.168.0.10 as our IP address to use:
664
665        curl -P 192.168.0.10 ftp.download.com
666
667NETWORK INTERFACE
668
669  Get a web page from a server using a specified port for the interface:
670
671        curl --interface eth0:1 http://www.netscape.com/
672
673  or
674
675        curl --interface 192.168.1.10 http://www.netscape.com/
676
677HTTPS
678
679  Secure HTTP requires SSL libraries to be installed and used when curl is
680  built. If that is done, curl is capable of retrieving and posting documents
681  using the HTTPS protocol.
682
683  Example:
684
685        curl https://www.secure-site.com
686
687  Curl is also capable of using your personal certificates to get/post files
688  from sites that require valid certificates. The only drawback is that the
689  certificate needs to be in PEM-format. PEM is a standard and open format to
690  store certificates with, but it is not used by the most commonly used
691  browsers (Netscape and MSIE both use the so called PKCS#12 format). If you
692  want curl to use the certificates you use with your (favourite) browser, you
693  may need to download/compile a converter that can convert your browser's
694  formatted certificates to PEM formatted ones. This kind of converter is
695  included in recent versions of OpenSSL, and for older versions Dr Stephen
696  N. Henson has written a patch for SSLeay that adds this functionality. You
697  can get his patch (that requires an SSLeay installation) from his site at:
698  http://www.drh-consultancy.demon.co.uk/
699
700  Example on how to automatically retrieve a document using a certificate with
701  a personal password:
702
703        curl -E /path/to/cert.pem:password https://secure.site.com/
704
705  If you neglect to specify the password on the command line, you will be
706  prompted for the correct password before any data can be received.
707
708  Many older SSL-servers have problems with SSLv3 or TLS, which newer versions
709  of OpenSSL etc use, therefore it is sometimes useful to specify what
710  SSL-version curl should use. Use -3, -2 or -1 to specify that exact SSL
711  version to use (for SSLv3, SSLv2 or TLSv1 respectively):
712
713        curl -2 https://secure.site.com/
714
715  Otherwise, curl will first attempt to use v3 and then v2.
716
717  To use OpenSSL to convert your favourite browser's certificate into a PEM
718  formatted one that curl can use, do something like this:
719
720    In Netscape, you start with hitting the 'Security' menu button.
721
722    Select 'certificates->yours' and then pick a certificate in the list
723
724    Press the 'Export' button
725
726    enter your PIN code for the certs
727
728    select a proper place to save it
729
730    Run the 'openssl' application to convert the certificate. If you cd to the
731    openssl installation, you can do it like:
732
733     # ./apps/openssl pkcs12 -in [file you saved] -clcerts -out [PEMfile]
734
735    In Firefox, select Options, then Advanced, then the Encryption tab,
736    View Certificates. This opens the Certificate Manager, where you can
737    Export. Be sure to select PEM for the Save as type.
738
739    In Internet Explorer, select Internet Options, then the Content tab, then
740    Certificates. Then you can Export, and depending on the format you may
741    need to convert to PEM.
742
743    In Chrome, select Settings, then Show Advanced Settings. Under HTTPS/SSL
744    select Manage Certificates.
745
746RESUMING FILE TRANSFERS
747
748 To continue a file transfer where it was previously aborted, curl supports
749 resume on HTTP(S) downloads as well as FTP uploads and downloads.
750
751 Continue downloading a document:
752
753        curl -C - -o file ftp://ftp.server.com/path/file
754
755 Continue uploading a document(*1):
756
757        curl -C - -T file ftp://ftp.server.com/path/file
758
759 Continue downloading a document from a web server(*2):
760
761        curl -C - -o file http://www.server.com/
762
763 (*1) = This requires that the FTP server supports the non-standard command
764        SIZE. If it doesn't, curl will say so.
765
766 (*2) = This requires that the web server supports at least HTTP/1.1. If it
767        doesn't, curl will say so.
768
769TIME CONDITIONS
770
771 HTTP allows a client to specify a time condition for the document it
772 requests. It is If-Modified-Since or If-Unmodified-Since. Curl allows you to
773 specify them with the -z/--time-cond flag.
774
775 For example, you can easily make a download that only gets performed if the
776 remote file is newer than a local copy. It would be made like:
777
778        curl -z local.html http://remote.server.com/remote.html
779
780 Or you can download a file only if the local file is newer than the remote
781 one. Do this by prepending the date string with a '-', as in:
782
783        curl -z -local.html http://remote.server.com/remote.html
784
785 You can specify a "free text" date as condition. Tell curl to only download
786 the file if it was updated since January 12, 2012:
787
788        curl -z "Jan 12 2012" http://remote.server.com/remote.html
789
790 Curl will then accept a wide range of date formats. You always make the date
791 check the other way around by prepending it with a dash '-'.
792
793DICT
794
795  For fun try
796
797        curl dict://dict.org/m:curl
798        curl dict://dict.org/d:heisenbug:jargon
799        curl dict://dict.org/d:daniel:web1913
800
801  Aliases for 'm' are 'match' and 'find', and aliases for 'd' are 'define'
802  and 'lookup'. For example,
803
804        curl dict://dict.org/find:curl
805
806  Commands that break the URL description of the RFC (but not the DICT
807  protocol) are
808
809        curl dict://dict.org/show:db
810        curl dict://dict.org/show:strat
811
812  Authentication is still missing (but this is not required by the RFC)
813
814LDAP
815
816  If you have installed the OpenLDAP library, curl can take advantage of it
817  and offer ldap:// support.
818
819  LDAP is a complex thing and writing an LDAP query is not an easy task. I do
820  advise you to dig up the syntax description for that elsewhere. Two places
821  that might suit you are:
822
823  Netscape's "Netscape Directory SDK 3.0 for C Programmer's Guide Chapter 10:
824  Working with LDAP URLs":
825  http://developer.netscape.com/docs/manuals/dirsdk/csdk30/url.htm
826
827  RFC 2255, "The LDAP URL Format" https://curl.haxx.se/rfc/rfc2255.txt
828
829  To show you an example, this is how I can get all people from my local LDAP
830  server that has a certain sub-domain in their email address:
831
832        curl -B "ldap://ldap.frontec.se/o=frontec??sub?mail=*sth.frontec.se"
833
834  If I want the same info in HTML format, I can get it by not using the -B
835  (enforce ASCII) flag.
836
837ENVIRONMENT VARIABLES
838
839  Curl reads and understands the following environment variables:
840
841        http_proxy, HTTPS_PROXY, FTP_PROXY
842
843  They should be set for protocol-specific proxies. General proxy should be
844  set with
845
846        ALL_PROXY
847
848  A comma-separated list of host names that shouldn't go through any proxy is
849  set in (only an asterisk, '*' matches all hosts)
850
851        NO_PROXY
852
853  If the host name matches one of these strings, or the host is within the
854  domain of one of these strings, transactions with that node will not be
855  proxied.
856
857
858  The usage of the -x/--proxy flag overrides the environment variables.
859
860NETRC
861
862  Unix introduced the .netrc concept a long time ago. It is a way for a user
863  to specify name and password for commonly visited FTP sites in a file so
864  that you don't have to type them in each time you visit those sites. You
865  realize this is a big security risk if someone else gets hold of your
866  passwords, so therefore most unix programs won't read this file unless it is
867  only readable by yourself (curl doesn't care though).
868
869  Curl supports .netrc files if told to (using the -n/--netrc and
870  --netrc-optional options). This is not restricted to just FTP,
871  so curl can use it for all protocols where authentication is used.
872
873  A very simple .netrc file could look something like:
874
875        machine curl.haxx.se login iamdaniel password mysecret
876
877CUSTOM OUTPUT
878
879  To better allow script programmers to get to know about the progress of
880  curl, the -w/--write-out option was introduced. Using this, you can specify
881  what information from the previous transfer you want to extract.
882
883  To display the amount of bytes downloaded together with some text and an
884  ending newline:
885
886        curl -w 'We downloaded %{size_download} bytes\n' www.download.com
887
888KERBEROS FTP TRANSFER
889
890  Curl supports kerberos4 and kerberos5/GSSAPI for FTP transfers. You need
891  the kerberos package installed and used at curl build time for it to be
892  available.
893
894  First, get the krb-ticket the normal way, like with the kinit/kauth tool.
895  Then use curl in way similar to:
896
897        curl --krb private ftp://krb4site.com -u username:fakepwd
898
899  There's no use for a password on the -u switch, but a blank one will make
900  curl ask for one and you already entered the real password to kinit/kauth.
901
902TELNET
903
904  The curl telnet support is basic and very easy to use. Curl passes all data
905  passed to it on stdin to the remote server. Connect to a remote telnet
906  server using a command line similar to:
907
908        curl telnet://remote.server.com
909
910  And enter the data to pass to the server on stdin. The result will be sent
911  to stdout or to the file you specify with -o.
912
913  You might want the -N/--no-buffer option to switch off the buffered output
914  for slow connections or similar.
915
916  Pass options to the telnet protocol negotiation, by using the -t option. To
917  tell the server we use a vt100 terminal, try something like:
918
919        curl -tTTYPE=vt100 telnet://remote.server.com
920
921  Other interesting options for it -t include:
922
923   - XDISPLOC=<X display> Sets the X display location.
924
925   - NEW_ENV=<var,val> Sets an environment variable.
926
927  NOTE: The telnet protocol does not specify any way to login with a specified
928  user and password so curl can't do that automatically. To do that, you need
929  to track when the login prompt is received and send the username and
930  password accordingly.
931
932PERSISTENT CONNECTIONS
933
934  Specifying multiple files on a single command line will make curl transfer
935  all of them, one after the other in the specified order.
936
937  libcurl will attempt to use persistent connections for the transfers so that
938  the second transfer to the same host can use the same connection that was
939  already initiated and was left open in the previous transfer. This greatly
940  decreases connection time for all but the first transfer and it makes a far
941  better use of the network.
942
943  Note that curl cannot use persistent connections for transfers that are used
944  in subsequence curl invokes. Try to stuff as many URLs as possible on the
945  same command line if they are using the same host, as that'll make the
946  transfers faster. If you use an HTTP proxy for file transfers, practically
947  all transfers will be persistent.
948
949MULTIPLE TRANSFERS WITH A SINGLE COMMAND LINE
950
951  As is mentioned above, you can download multiple files with one command line
952  by simply adding more URLs. If you want those to get saved to a local file
953  instead of just printed to stdout, you need to add one save option for each
954  URL you specify. Note that this also goes for the -O option (but not
955  --remote-name-all).
956
957  For example: get two files and use -O for the first and a custom file
958  name for the second:
959
960    curl -O http://url.com/file.txt ftp://ftp.com/moo.exe -o moo.jpg
961
962  You can also upload multiple files in a similar fashion:
963
964    curl -T local1 ftp://ftp.com/moo.exe -T local2 ftp://ftp.com/moo2.txt
965
966IPv6
967
968  curl will connect to a server with IPv6 when a host lookup returns an IPv6
969  address and fall back to IPv4 if the connection fails. The --ipv4 and --ipv6
970  options can specify which address to use when both are available. IPv6
971  addresses can also be specified directly in URLs using the syntax:
972
973    http://[2001:1890:1112:1::20]/overview.html
974
975  When this style is used, the -g option must be given to stop curl from
976  interpreting the square brackets as special globbing characters.  Link local
977  and site local addresses including a scope identifier, such as fe80::1234%1,
978  may also be used, but the scope portion must be numeric or match an existing
979  network interface on Linux and the percent character must be URL escaped. The
980  previous example in an SFTP URL might look like:
981
982    sftp://[fe80::1234%251]/
983
984  IPv6 addresses provided other than in URLs (e.g. to the --proxy, --interface
985  or --ftp-port options) should not be URL encoded.
986
987METALINK
988
989  Curl supports Metalink (both version 3 and 4 (RFC 5854) are supported), a way
990  to list multiple URIs and hashes for a file. Curl will make use of the mirrors
991  listed within for failover if there are errors (such as the file or server not
992  being available). It will also verify the hash of the file after the download
993  completes. The Metalink file itself is downloaded and processed in memory and
994  not stored in the local file system.
995
996  Example to use a remote Metalink file:
997
998    curl --metalink http://www.example.com/example.metalink
999
1000  To use a Metalink file in the local file system, use FILE protocol (file://):
1001
1002    curl --metalink file://example.metalink
1003
1004  Please note that if FILE protocol is disabled, there is no way to use a local
1005  Metalink file at the time of this writing. Also note that if --metalink and
1006  --include are used together, --include will be ignored. This is because including
1007  headers in the response will break Metalink parser and if the headers are included
1008  in the file described in Metalink file, hash check will fail.
1009
1010MAILING LISTS
1011
1012  For your convenience, we have several open mailing lists to discuss curl,
1013  its development and things relevant to this. Get all info at
1014  https://curl.haxx.se/mail/. Some of the lists available are:
1015
1016  curl-users
1017
1018    Users of the command line tool. How to use it, what doesn't work, new
1019    features, related tools, questions, news, installations, compilations,
1020    running, porting etc.
1021
1022  curl-library
1023
1024    Developers using or developing libcurl. Bugs, extensions, improvements.
1025
1026  curl-announce
1027
1028    Low-traffic. Only receives announcements of new public versions. At worst,
1029    that makes something like one or two mails per month, but usually only one
1030    mail every second month.
1031
1032  curl-and-php
1033
1034    Using the curl functions in PHP. Everything curl with a PHP angle. Or PHP
1035    with a curl angle.
1036
1037  curl-and-python
1038
1039    Python hackers using curl with or without the python binding pycurl.
1040
1041  Please direct curl questions, feature requests and trouble reports to one of
1042  these mailing lists instead of mailing any individual.
1043