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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1 # curl tutorial
2
3 ## Simple Usage
4
5 Get the main page from Netscape's web-server:
6
7 curl http://www.netscape.com/
8
9 Get the README file the user's home directory at funet's ftp-server:
10
11 curl ftp://ftp.funet.fi/README
12
13 Get a web page from a server using port 8000:
14
15 curl http://www.weirdserver.com:8000/
16
17 Get a directory listing of an FTP site:
18
19 curl ftp://cool.haxx.se/
20
21 Get the definition of curl from a dictionary:
22
23 curl dict://dict.org/m:curl
24
25 Fetch two documents at once:
26
27 curl ftp://cool.haxx.se/ http://www.weirdserver.com:8000/
28
29 Get a file off an FTPS server:
30
31 curl ftps://files.are.secure.com/secrets.txt
32
33 or use the more appropriate FTPS way to get the same file:
34
35 curl --ftp-ssl ftp://files.are.secure.com/secrets.txt
36
37 Get a file from an SSH server using SFTP:
38
39 curl -u username sftp://example.com/etc/issue
40
41 Get a file from an SSH server using SCP using a private key (not
42 password-protected) to authenticate:
43
44 curl -u username: --key ~/.ssh/id_rsa scp://example.com/~/file.txt
45
46 Get a file from an SSH server using SCP using a private key
47 (password-protected) to authenticate:
48
49 curl -u username: --key ~/.ssh/id_rsa --pass private_key_password
50 scp://example.com/~/file.txt
51
52 Get the main page from an IPv6 web server:
53
54 curl "http://[2001:1890:1112:1::20]/"
55
56 Get a file from an SMB server:
57
58 curl -u "domain\username:passwd" smb://server.example.com/share/file.txt
59
60 ## Download to a File
61
62 Get a web page and store in a local file with a specific name:
63
64 curl -o thatpage.html http://www.netscape.com/
65
66 Get a web page and store in a local file, make the local file get the name of
67 the remote document (if no file name part is specified in the URL, this will
68 fail):
69
70 curl -O http://www.netscape.com/index.html
71
72 Fetch two files and store them with their remote names:
73
74 curl -O www.haxx.se/index.html -O curl.haxx.se/download.html
75
76 ## Using Passwords
77
78 ### FTP
79
80 To ftp files using name+passwd, include them in the URL like:
81
82 curl ftp://name:passwd@machine.domain:port/full/path/to/file
83
84 or specify them with the -u flag like
85
86 curl -u name:passwd ftp://machine.domain:port/full/path/to/file
87
88 ### FTPS
89
90 It is just like for FTP, but you may also want to specify and use SSL-specific
91 options for certificates etc.
92
93 Note that using `FTPS://` as prefix is the "implicit" way as described in the
94 standards while the recommended "explicit" way is done by using FTP:// and the
95 `--ftp-ssl` option.
96
97 ### SFTP / SCP
98
99 This is similar to FTP, but you can use the `--key` option to specify a
100 private key to use instead of a password. Note that the private key may itself
101 be protected by a password that is unrelated to the login password of the
102 remote system; this password is specified using the `--pass` option.
103 Typically, curl will automatically extract the public key from the private key
104 file, but in cases where curl does not have the proper library support, a
105 matching public key file must be specified using the `--pubkey` option.
106
107 ### HTTP
108
109 Curl also supports user and password in HTTP URLs, thus you can pick a file
110 like:
111
112 curl http://name:passwd@machine.domain/full/path/to/file
113
114 or specify user and password separately like in
115
116 curl -u name:passwd http://machine.domain/full/path/to/file
117
118 HTTP offers many different methods of authentication and curl supports
119 several: Basic, Digest, NTLM and Negotiate (SPNEGO). Without telling which
120 method to use, curl defaults to Basic. You can also ask curl to pick the most
121 secure ones out of the ones that the server accepts for the given URL, by
122 using `--anyauth`.
123
124 **Note**! According to the URL specification, HTTP URLs can not contain a user
125 and password, so that style will not work when using curl via a proxy, even
126 though curl allows it at other times. When using a proxy, you _must_ use the
127 `-u` style for user and password.
128
129 ### HTTPS
130
131 Probably most commonly used with private certificates, as explained below.
132
133 ## Proxy
134
135 curl supports both HTTP and SOCKS proxy servers, with optional authentication.
136 It does not have special support for FTP proxy servers since there are no
137 standards for those, but it can still be made to work with many of them. You
138 can also use both HTTP and SOCKS proxies to transfer files to and from FTP
139 servers.
140
141 Get an ftp file using an HTTP proxy named my-proxy that uses port 888:
142
143 curl -x my-proxy:888 ftp://ftp.leachsite.com/README
144
145 Get a file from an HTTP server that requires user and password, using the
146 same proxy as above:
147
148 curl -u user:passwd -x my-proxy:888 http://www.get.this/
149
150 Some proxies require special authentication. Specify by using -U as above:
151
152 curl -U user:passwd -x my-proxy:888 http://www.get.this/
153
154 A comma-separated list of hosts and domains which do not use the proxy can be
155 specified as:
156
157 curl --noproxy localhost,get.this -x my-proxy:888 http://www.get.this/
158
159 If the proxy is specified with `--proxy1.0` instead of `--proxy` or `-x`, then
160 curl will use HTTP/1.0 instead of HTTP/1.1 for any `CONNECT` attempts.
161
162 curl also supports SOCKS4 and SOCKS5 proxies with `--socks4` and `--socks5`.
163
164 See also the environment variables Curl supports that offer further proxy
165 control.
166
167 Most FTP proxy servers are set up to appear as a normal FTP server from the
168 client's perspective, with special commands to select the remote FTP server.
169 curl supports the `-u`, `-Q` and `--ftp-account` options that can be used to
170 set up transfers through many FTP proxies. For example, a file can be uploaded
171 to a remote FTP server using a Blue Coat FTP proxy with the options:
172
173 curl -u "username@ftp.server Proxy-Username:Remote-Pass"
174 --ftp-account Proxy-Password --upload-file local-file
175 ftp://my-ftp.proxy.server:21/remote/upload/path/
176
177 See the manual for your FTP proxy to determine the form it expects to set up
178 transfers, and curl's `-v` option to see exactly what curl is sending.
179
180 ## Ranges
181
182 HTTP 1.1 introduced byte-ranges. Using this, a client can request to get only
183 one or more subparts of a specified document. Curl supports this with the `-r`
184 flag.
185
186 Get the first 100 bytes of a document:
187
188 curl -r 0-99 http://www.get.this/
189
190 Get the last 500 bytes of a document:
191
192 curl -r -500 http://www.get.this/
193
194 Curl also supports simple ranges for FTP files as well. Then you can only
195 specify start and stop position.
196
197 Get the first 100 bytes of a document using FTP:
198
199 curl -r 0-99 ftp://www.get.this/README
200
201 ## Uploading
202
203 ### FTP / FTPS / SFTP / SCP
204
205 Upload all data on stdin to a specified server:
206
207 curl -T - ftp://ftp.upload.com/myfile
208
209 Upload data from a specified file, login with user and password:
210
211 curl -T uploadfile -u user:passwd ftp://ftp.upload.com/myfile
212
213 Upload a local file to the remote site, and use the local file name at the
214 remote site too:
215
216 curl -T uploadfile -u user:passwd ftp://ftp.upload.com/
217
218 Upload a local file to get appended to the remote file:
219
220 curl -T localfile -a ftp://ftp.upload.com/remotefile
221
222 Curl also supports ftp upload through a proxy, but only if the proxy is
223 configured to allow that kind of tunneling. If it does, you can run curl in a
224 fashion similar to:
225
226 curl --proxytunnel -x proxy:port -T localfile ftp.upload.com
227
228 ### SMB / SMBS
229
230 curl -T file.txt -u "domain\username:passwd"
231 smb://server.example.com/share/
232
233 ### HTTP
234
235 Upload all data on stdin to a specified HTTP site:
236
237 curl -T - http://www.upload.com/myfile
238
239 Note that the HTTP server must have been configured to accept PUT before this
240 can be done successfully.
241
242 For other ways to do HTTP data upload, see the POST section below.
243
244 ## Verbose / Debug
245
246 If curl fails where it isn't supposed to, if the servers don't let you in, if
247 you can't understand the responses: use the `-v` flag to get verbose
248 fetching. Curl will output lots of info and what it sends and receives in
249 order to let the user see all client-server interaction (but it won't show you
250 the actual data).
251
252 curl -v ftp://ftp.upload.com/
253
254 To get even more details and information on what curl does, try using the
255 `--trace` or `--trace-ascii` options with a given file name to log to, like
256 this:
257
258 curl --trace trace.txt www.haxx.se
259
260
261 ## Detailed Information
262
263 Different protocols provide different ways of getting detailed information
264 about specific files/documents. To get curl to show detailed information about
265 a single file, you should use `-I`/`--head` option. It displays all available
266 info on a single file for HTTP and FTP. The HTTP information is a lot more
267 extensive.
268
269 For HTTP, you can get the header information (the same as `-I` would show)
270 shown before the data by using `-i`/`--include`. Curl understands the
271 `-D`/`--dump-header` option when getting files from both FTP and HTTP, and it
272 will then store the headers in the specified file.
273
274 Store the HTTP headers in a separate file (headers.txt in the example):
275
276 curl --dump-header headers.txt curl.haxx.se
277
278 Note that headers stored in a separate file can be very useful at a later time
279 if you want curl to use cookies sent by the server. More about that in the
280 cookies section.
281
282 ## POST (HTTP)
283
284 It's easy to post data using curl. This is done using the `-d <data>` option.
285 The post data must be urlencoded.
286
287 Post a simple "name" and "phone" guestbook.
288
289 curl -d "name=Rafael%20Sagula&phone=3320780" http://www.where.com/guest.cgi
290
291 How to post a form with curl, lesson #1:
292
293 Dig out all the `<input>` tags in the form that you want to fill in.
294
295 If there's a "normal" post, you use `-d` to post. `-d` takes a full "post
296 string", which is in the format
297
298 <variable1>=<data1>&<variable2>=<data2>&...
299
300 The 'variable' names are the names set with `"name="` in the `<input>` tags,
301 and the data is the contents you want to fill in for the inputs. The data
302 *must* be properly URL encoded. That means you replace space with + and that
303 you replace weird letters with %XX where XX is the hexadecimal representation
304 of the letter's ASCII code.
305
306 Example:
307
308 (page located at `http://www.formpost.com/getthis/`)
309
310 <form action="post.cgi" method="post">
311 <input name=user size=10>
312 <input name=pass type=password size=10>
313 <input name=id type=hidden value="blablabla">
314 <input name=ding value="submit">
315 </form>
316
317 We want to enter user 'foobar' with password '12345'.
318
319 To post to this, you enter a curl command line like:
320
321 curl -d "user=foobar&pass=12345&id=blablabla&ding=submit"
322 http://www.formpost.com/getthis/post.cgi
323
324 While `-d` uses the application/x-www-form-urlencoded mime-type, generally
325 understood by CGI's and similar, curl also supports the more capable
326 multipart/form-data type. This latter type supports things like file upload.
327
328 `-F` accepts parameters like `-F "name=contents"`. If you want the contents to
329 be read from a file, use `@filename` as contents. When specifying a file, you
330 can also specify the file content type by appending `;type=<mime type>` to the
331 file name. You can also post the contents of several files in one field. For
332 example, the field name 'coolfiles' is used to send three files, with
333 different content types using the following syntax:
334
335 curl -F "coolfiles=@fil1.gif;type=image/gif,fil2.txt,fil3.html"
336 http://www.post.com/postit.cgi
337
338 If the content-type is not specified, curl will try to guess from the file
339 extension (it only knows a few), or use the previously specified type (from an
340 earlier file if several files are specified in a list) or else it will use the
341 default type 'application/octet-stream'.
342
343 Emulate a fill-in form with `-F`. Let's say you fill in three fields in a
344 form. One field is a file name which to post, one field is your name and one
345 field is a file description. We want to post the file we have written named
346 "cooltext.txt". To let curl do the posting of this data instead of your
347 favourite browser, you have to read the HTML source of the form page and find
348 the names of the input fields. In our example, the input field names are
349 'file', 'yourname' and 'filedescription'.
350
351 curl -F "file=@cooltext.txt" -F "yourname=Daniel"
352 -F "filedescription=Cool text file with cool text inside"
353 http://www.post.com/postit.cgi
354
355 To send two files in one post you can do it in two ways:
356
357 Send multiple files in a single "field" with a single field name:
358
359 curl -F "pictures=@dog.gif,cat.gif" $URL
360
361 Send two fields with two field names
362
363 curl -F "docpicture=@dog.gif" -F "catpicture=@cat.gif" $URL
364
365 To send a field value literally without interpreting a leading `@` or `<`, or
366 an embedded `;type=`, use `--form-string` instead of `-F`. This is recommended
367 when the value is obtained from a user or some other unpredictable
368 source. Under these circumstances, using `-F` instead of `--form-string` could
369 allow a user to trick curl into uploading a file.
370
371 ## Referrer
372
373 An HTTP request has the option to include information about which address
374 referred it to the actual page. Curl allows you to specify the referrer to be
375 used on the command line. It is especially useful to fool or trick stupid
376 servers or CGI scripts that rely on that information being available or
377 contain certain data.
378
379 curl -e www.coolsite.com http://www.showme.com/
380
381 ## User Agent
382
383 An HTTP request has the option to include information about the browser that
384 generated the request. Curl allows it to be specified on the command line. It
385 is especially useful to fool or trick stupid servers or CGI scripts that only
386 accept certain browsers.
387
388 Example:
389
390 curl -A 'Mozilla/3.0 (Win95; I)' http://www.nationsbank.com/
391
392 Other common strings:
393
394 - `Mozilla/3.0 (Win95; I)` - Netscape Version 3 for Windows 95
395 - `Mozilla/3.04 (Win95; U)` - Netscape Version 3 for Windows 95
396 - `Mozilla/2.02 (OS/2; U)` - Netscape Version 2 for OS/2
397 - `Mozilla/4.04 [en] (X11; U; AIX 4.2; Nav)` - Netscape for AIX
398 - `Mozilla/4.05 [en] (X11; U; Linux 2.0.32 i586)` - Netscape for Linux
399
400 Note that Internet Explorer tries hard to be compatible in every way:
401
402 - `Mozilla/4.0 (compatible; MSIE 4.01; Windows 95)` - MSIE for W95
403
404 Mozilla is not the only possible User-Agent name:
405
406 - `Konqueror/1.0` - KDE File Manager desktop client
407 - `Lynx/2.7.1 libwww-FM/2.14` - Lynx command line browser
408
409 ## Cookies
410
411 Cookies are generally used by web servers to keep state information at the
412 client's side. The server sets cookies by sending a response line in the
413 headers that looks like `Set-Cookie: <data>` where the data part then
414 typically contains a set of `NAME=VALUE` pairs (separated by semicolons `;`
415 like `NAME1=VALUE1; NAME2=VALUE2;`). The server can also specify for what path
416 the "cookie" should be used for (by specifying `path=value`), when the cookie
417 should expire (`expire=DATE`), for what domain to use it (`domain=NAME`) and
418 if it should be used on secure connections only (`secure`).
419
420 If you've received a page from a server that contains a header like:
421
422 Set-Cookie: sessionid=boo123; path="/foo";
423
424 it means the server wants that first pair passed on when we get anything in a
425 path beginning with "/foo".
426
427 Example, get a page that wants my name passed in a cookie:
428
429 curl -b "name=Daniel" www.sillypage.com
430
431 Curl also has the ability to use previously received cookies in following
432 sessions. If you get cookies from a server and store them in a file in a
433 manner similar to:
434
435 curl --dump-header headers www.example.com
436
437 ... you can then in a second connect to that (or another) site, use the
438 cookies from the 'headers' file like:
439
440 curl -b headers www.example.com
441
442 While saving headers to a file is a working way to store cookies, it is
443 however error-prone and not the preferred way to do this. Instead, make curl
444 save the incoming cookies using the well-known netscape cookie format like
445 this:
446
447 curl -c cookies.txt www.example.com
448
449 Note that by specifying `-b` you enable the "cookie awareness" and with `-L`
450 you can make curl follow a location: (which often is used in combination with
451 cookies). So that if a site sends cookies and a location, you can use a
452 non-existing file to trigger the cookie awareness like:
453
454 curl -L -b empty.txt www.example.com
455
456 The file to read cookies from must be formatted using plain HTTP headers OR as
457 netscape's cookie file. Curl will determine what kind it is based on the file
458 contents. In the above command, curl will parse the header and store the
459 cookies received from www.example.com. curl will send to the server the
460 stored cookies which match the request as it follows the location. The file
461 "empty.txt" may be a nonexistent file.
462
463 To read and write cookies from a netscape cookie file, you can set both `-b`
464 and `-c` to use the same file:
465
466 curl -b cookies.txt -c cookies.txt www.example.com
467
468 ## Progress Meter
469
470 The progress meter exists to show a user that something actually is
471 happening. The different fields in the output have the following meaning:
472
473 % Total % Received % Xferd Average Speed Time Curr.
474 Dload Upload Total Current Left Speed
475 0 151M 0 38608 0 0 9406 0 4:41:43 0:00:04 4:41:39 9287
476
477 From left-to-right:
478
479 - % - percentage completed of the whole transfer
480 - Total - total size of the whole expected transfer
481 - % - percentage completed of the download
482 - Received - currently downloaded amount of bytes
483 - % - percentage completed of the upload
484 - Xferd - currently uploaded amount of bytes
485 - Average Speed Dload - the average transfer speed of the download
486 - Average Speed Upload - the average transfer speed of the upload
487 - Time Total - expected time to complete the operation
488 - Time Current - time passed since the invoke
489 - Time Left - expected time left to completion
490 - Curr.Speed - the average transfer speed the last 5 seconds (the first
491 5 seconds of a transfer is based on less time of course.)
492
493 The `-#` option will display a totally different progress bar that doesn't
494 need much explanation!
495
496 ## Speed Limit
497
498 Curl allows the user to set the transfer speed conditions that must be met to
499 let the transfer keep going. By using the switch `-y` and `-Y` you can make
500 curl abort transfers if the transfer speed is below the specified lowest limit
501 for a specified time.
502
503 To have curl abort the download if the speed is slower than 3000 bytes per
504 second for 1 minute, run:
505
506 curl -Y 3000 -y 60 www.far-away-site.com
507
508 This can very well be used in combination with the overall time limit, so
509 that the above operation must be completed in whole within 30 minutes:
510
511 curl -m 1800 -Y 3000 -y 60 www.far-away-site.com
512
513 Forcing curl not to transfer data faster than a given rate is also possible,
514 which might be useful if you're using a limited bandwidth connection and you
515 don't want your transfer to use all of it (sometimes referred to as
516 "bandwidth throttle").
517
518 Make curl transfer data no faster than 10 kilobytes per second:
519
520 curl --limit-rate 10K www.far-away-site.com
521
522 or
523
524 curl --limit-rate 10240 www.far-away-site.com
525
526 Or prevent curl from uploading data faster than 1 megabyte per second:
527
528 curl -T upload --limit-rate 1M ftp://uploadshereplease.com
529
530 When using the `--limit-rate` option, the transfer rate is regulated on a
531 per-second basis, which will cause the total transfer speed to become lower
532 than the given number. Sometimes of course substantially lower, if your
533 transfer stalls during periods.
534
535 ## Config File
536
537 Curl automatically tries to read the `.curlrc` file (or `_curlrc` file on
538 Microsoft Windows systems) from the user's home dir on startup.
539
540 The config file could be made up with normal command line switches, but you
541 can also specify the long options without the dashes to make it more
542 readable. You can separate the options and the parameter with spaces, or with
543 `=` or `:`. Comments can be used within the file. If the first letter on a
544 line is a `#`-symbol the rest of the line is treated as a comment.
545
546 If you want the parameter to contain spaces, you must enclose the entire
547 parameter within double quotes (`"`). Within those quotes, you specify a quote
548 as `\"`.
549
550 NOTE: You must specify options and their arguments on the same line.
551
552 Example, set default time out and proxy in a config file:
553
554 # We want a 30 minute timeout:
555 -m 1800
556 # ... and we use a proxy for all accesses:
557 proxy = proxy.our.domain.com:8080
558
559 White spaces ARE significant at the end of lines, but all white spaces leading
560 up to the first characters of each line are ignored.
561
562 Prevent curl from reading the default file by using -q as the first command
563 line parameter, like:
564
565 curl -q www.thatsite.com
566
567 Force curl to get and display a local help page in case it is invoked without
568 URL by making a config file similar to:
569
570 # default url to get
571 url = "http://help.with.curl.com/curlhelp.html"
572
573 You can specify another config file to be read by using the `-K`/`--config`
574 flag. If you set config file name to `-` it'll read the config from stdin,
575 which can be handy if you want to hide options from being visible in process
576 tables etc:
577
578 echo "user = user:passwd" | curl -K - http://that.secret.site.com
579
580 ## Extra Headers
581
582 When using curl in your own very special programs, you may end up needing
583 to pass on your own custom headers when getting a web page. You can do
584 this by using the `-H` flag.
585
586 Example, send the header `X-you-and-me: yes` to the server when getting a
587 page:
588
589 curl -H "X-you-and-me: yes" www.love.com
590
591 This can also be useful in case you want curl to send a different text in a
592 header than it normally does. The `-H` header you specify then replaces the
593 header curl would normally send. If you replace an internal header with an
594 empty one, you prevent that header from being sent. To prevent the `Host:`
595 header from being used:
596
597 curl -H "Host:" www.server.com
598
599 ## FTP and Path Names
600
601 Do note that when getting files with a `ftp://` URL, the given path is
602 relative the directory you enter. To get the file `README` from your home
603 directory at your ftp site, do:
604
605 curl ftp://user:passwd@my.site.com/README
606
607 But if you want the README file from the root directory of that very same
608 site, you need to specify the absolute file name:
609
610 curl ftp://user:passwd@my.site.com//README
611
612 (I.e with an extra slash in front of the file name.)
613
614 ## SFTP and SCP and Path Names
615
616 With sftp: and scp: URLs, the path name given is the absolute name on the
617 server. To access a file relative to the remote user's home directory, prefix
618 the file with `/~/` , such as:
619
620 curl -u $USER sftp://home.example.com/~/.bashrc
621
622 ## FTP and Firewalls
623
624 The FTP protocol requires one of the involved parties to open a second
625 connection as soon as data is about to get transferred. There are two ways to
626 do this.
627
628 The default way for curl is to issue the PASV command which causes the server
629 to open another port and await another connection performed by the
630 client. This is good if the client is behind a firewall that doesn't allow
631 incoming connections.
632
633 curl ftp.download.com
634
635 If the server, for example, is behind a firewall that doesn't allow
636 connections on ports other than 21 (or if it just doesn't support the `PASV`
637 command), the other way to do it is to use the `PORT` command and instruct the
638 server to connect to the client on the given IP number and port (as parameters
639 to the PORT command).
640
641 The `-P` flag to curl supports a few different options. Your machine may have
642 several IP-addresses and/or network interfaces and curl allows you to select
643 which of them to use. Default address can also be used:
644
645 curl -P - ftp.download.com
646
647 Download with `PORT` but use the IP address of our `le0` interface (this does
648 not work on windows):
649
650 curl -P le0 ftp.download.com
651
652 Download with `PORT` but use 192.168.0.10 as our IP address to use:
653
654 curl -P 192.168.0.10 ftp.download.com
655
656 ## Network Interface
657
658 Get a web page from a server using a specified port for the interface:
659
660 curl --interface eth0:1 http://www.netscape.com/
661
662 or
663
664 curl --interface 192.168.1.10 http://www.netscape.com/
665
666 ## HTTPS
667
668 Secure HTTP requires a TLS library to be installed and used when curl is
669 built. If that is done, curl is capable of retrieving and posting documents
670 using the HTTPS protocol.
671
672 Example:
673
674 curl https://www.secure-site.com
675
676 curl is also capable of using client certificates to get/post files from sites
677 that require valid certificates. The only drawback is that the certificate
678 needs to be in PEM-format. PEM is a standard and open format to store
679 certificates with, but it is not used by the most commonly used browsers. If
680 you want curl to use the certificates you use with your (favourite) browser,
681 you may need to download/compile a converter that can convert your browser's
682 formatted certificates to PEM formatted ones.
683
684 Example on how to automatically retrieve a document using a certificate with a
685 personal password:
686
687 curl -E /path/to/cert.pem:password https://secure.site.com/
688
689 If you neglect to specify the password on the command line, you will be
690 prompted for the correct password before any data can be received.
691
692 Many older HTTPS servers have problems with specific SSL or TLS versions,
693 which newer versions of OpenSSL etc use, therefore it is sometimes useful to
694 specify what SSL-version curl should use. Use -3, -2 or -1 to specify that
695 exact SSL version to use (for SSLv3, SSLv2 or TLSv1 respectively):
696
697 curl -2 https://secure.site.com/
698
699 Otherwise, curl will attempt to use a sensible TLS default version.
700
701 ## Resuming File Transfers
702
703 To continue a file transfer where it was previously aborted, curl supports
704 esume on HTTP(S) downloads as well as FTP uploads and downloads.
705
706 Continue downloading a document:
707
708 curl -C - -o file ftp://ftp.server.com/path/file
709
710 Continue uploading a document:
711
712 curl -C - -T file ftp://ftp.server.com/path/file
713
714 Continue downloading a document from a web server
715
716 curl -C - -o file http://www.server.com/
717
718 ## Time Conditions
719
720 HTTP allows a client to specify a time condition for the document it requests.
721 It is `If-Modified-Since` or `If-Unmodified-Since`. curl allows you to specify
722 them with the `-z`/`--time-cond` flag.
723
724 For example, you can easily make a download that only gets performed if the
725 remote file is newer than a local copy. It would be made like:
726
727 curl -z local.html http://remote.server.com/remote.html
728
729 Or you can download a file only if the local file is newer than the remote
730 one. Do this by prepending the date string with a `-`, as in:
731
732 curl -z -local.html http://remote.server.com/remote.html
733
734 You can specify a "free text" date as condition. Tell curl to only download
735 the file if it was updated since January 12, 2012:
736
737 curl -z "Jan 12 2012" http://remote.server.com/remote.html
738
739 Curl will then accept a wide range of date formats. You always make the date
740 check the other way around by prepending it with a dash (`-`).
741
742 ## DICT
743
744 For fun try
745
746 curl dict://dict.org/m:curl
747 curl dict://dict.org/d:heisenbug:jargon
748 curl dict://dict.org/d:daniel:web1913
749
750 Aliases for 'm' are 'match' and 'find', and aliases for 'd' are 'define' and
751 'lookup'. For example,
752
753 curl dict://dict.org/find:curl
754
755 Commands that break the URL description of the RFC (but not the DICT
756 protocol) are
757
758 curl dict://dict.org/show:db
759 curl dict://dict.org/show:strat
760
761 Authentication support is still missing
762
763 ## LDAP
764
765 If you have installed the OpenLDAP library, curl can take advantage of it and
766 offer `ldap://` support. On Windows, curl will use WinLDAP from Platform SDK
767 by default.
768
769 Default protocol version used by curl is LDAPv3. LDAPv2 will be used as
770 fallback mechanism in case if LDAPv3 will fail to connect.
771
772 LDAP is a complex thing and writing an LDAP query is not an easy task. I do
773 advise you to dig up the syntax description for that elsewhere. One such place
774 might be: [RFC 2255, The LDAP URL
775 Format](https://curl.haxx.se/rfc/rfc2255.txt)
776
777 To show you an example, this is how I can get all people from my local LDAP
778 server that has a certain sub-domain in their email address:
779
780 curl -B "ldap://ldap.frontec.se/o=frontec??sub?mail=*sth.frontec.se"
781
782 If I want the same info in HTML format, I can get it by not using the `-B`
783 (enforce ASCII) flag.
784
785 You also can use authentication when accessing LDAP catalog:
786
787 curl -u user:passwd "ldap://ldap.frontec.se/o=frontec??sub?mail=*"
788 curl "ldap://user:passwd@ldap.frontec.se/o=frontec??sub?mail=*"
789
790 By default, if user and password provided, OpenLDAP/WinLDAP will use basic
791 authentication. On Windows you can control this behavior by providing one of
792 `--basic`, `--ntlm` or `--digest` option in curl command line
793
794 curl --ntlm "ldap://user:passwd@ldap.frontec.se/o=frontec??sub?mail=*"
795
796 On Windows, if no user/password specified, auto-negotiation mechanism will be
797 used with current logon credentials (SSPI/SPNEGO).
798
799 ## Environment Variables
800
801 Curl reads and understands the following environment variables:
802
803 http_proxy, HTTPS_PROXY, FTP_PROXY
804
805 They should be set for protocol-specific proxies. General proxy should be set
806 with
807
808 ALL_PROXY
809
810 A comma-separated list of host names that shouldn't go through any proxy is
811 set in (only an asterisk, `*` matches all hosts)
812
813 NO_PROXY
814
815 If the host name matches one of these strings, or the host is within the
816 domain of one of these strings, transactions with that node will not be
817 proxied. When a domain is used, it needs to start with a period. A user can
818 specify that both www.example.com and foo.example.com should not use a proxy
819 by setting `NO_PROXY` to `.example.com`. By including the full name you can
820 exclude specific host names, so to make `www.example.com` not use a proxy but
821 still have `foo.example.com` do it, set `NO_PROXY` to `www.example.com`.
822
823 The usage of the `-x`/`--proxy` flag overrides the environment variables.
824
825 ## Netrc
826
827 Unix introduced the `.netrc` concept a long time ago. It is a way for a user
828 to specify name and password for commonly visited FTP sites in a file so that
829 you don't have to type them in each time you visit those sites. You realize
830 this is a big security risk if someone else gets hold of your passwords, so
831 therefore most unix programs won't read this file unless it is only readable
832 by yourself (curl doesn't care though).
833
834 Curl supports `.netrc` files if told to (using the `-n`/`--netrc` and
835 `--netrc-optional` options). This is not restricted to just FTP, so curl can
836 use it for all protocols where authentication is used.
837
838 A very simple `.netrc` file could look something like:
839
840 machine curl.haxx.se login iamdaniel password mysecret
841
842 ## Custom Output
843
844 To better allow script programmers to get to know about the progress of curl,
845 the `-w`/`--write-out` option was introduced. Using this, you can specify what
846 information from the previous transfer you want to extract.
847
848 To display the amount of bytes downloaded together with some text and an
849 ending newline:
850
851 curl -w 'We downloaded %{size_download} bytes\n' www.download.com
852
853 ## Kerberos FTP Transfer
854
855 Curl supports kerberos4 and kerberos5/GSSAPI for FTP transfers. You need the
856 kerberos package installed and used at curl build time for it to be available.
857
858 First, get the krb-ticket the normal way, like with the kinit/kauth tool.
859 Then use curl in way similar to:
860
861 curl --krb private ftp://krb4site.com -u username:fakepwd
862
863 There's no use for a password on the `-u` switch, but a blank one will make
864 curl ask for one and you already entered the real password to kinit/kauth.
865
866 ## TELNET
867
868 The curl telnet support is basic and very easy to use. Curl passes all data
869 passed to it on stdin to the remote server. Connect to a remote telnet server
870 using a command line similar to:
871
872 curl telnet://remote.server.com
873
874 And enter the data to pass to the server on stdin. The result will be sent to
875 stdout or to the file you specify with `-o`.
876
877 You might want the `-N`/`--no-buffer` option to switch off the buffered output
878 for slow connections or similar.
879
880 Pass options to the telnet protocol negotiation, by using the `-t` option. To
881 tell the server we use a vt100 terminal, try something like:
882
883 curl -tTTYPE=vt100 telnet://remote.server.com
884
885 Other interesting options for it `-t` include:
886
887 - `XDISPLOC=<X display>` Sets the X display location.
888 - `NEW_ENV=<var,val>` Sets an environment variable.
889
890 NOTE: The telnet protocol does not specify any way to login with a specified
891 user and password so curl can't do that automatically. To do that, you need to
892 track when the login prompt is received and send the username and password
893 accordingly.
894
895 ## Persistent Connections
896
897 Specifying multiple files on a single command line will make curl transfer all
898 of them, one after the other in the specified order.
899
900 libcurl will attempt to use persistent connections for the transfers so that
901 the second transfer to the same host can use the same connection that was
902 already initiated and was left open in the previous transfer. This greatly
903 decreases connection time for all but the first transfer and it makes a far
904 better use of the network.
905
906 Note that curl cannot use persistent connections for transfers that are used
907 in subsequence curl invokes. Try to stuff as many URLs as possible on the same
908 command line if they are using the same host, as that'll make the transfers
909 faster. If you use an HTTP proxy for file transfers, practically all transfers
910 will be persistent.
911
912 ## Multiple Transfers With A Single Command Line
913
914 As is mentioned above, you can download multiple files with one command line
915 by simply adding more URLs. If you want those to get saved to a local file
916 instead of just printed to stdout, you need to add one save option for each
917 URL you specify. Note that this also goes for the `-O` option (but not
918 `--remote-name-all`).
919
920 For example: get two files and use `-O` for the first and a custom file
921 name for the second:
922
923 curl -O http://url.com/file.txt ftp://ftp.com/moo.exe -o moo.jpg
924
925 You can also upload multiple files in a similar fashion:
926
927 curl -T local1 ftp://ftp.com/moo.exe -T local2 ftp://ftp.com/moo2.txt
928
929 ## IPv6
930
931 curl will connect to a server with IPv6 when a host lookup returns an IPv6
932 address and fall back to IPv4 if the connection fails. The `--ipv4` and
933 `--ipv6` options can specify which address to use when both are
934 available. IPv6 addresses can also be specified directly in URLs using the
935 syntax:
936
937 http://[2001:1890:1112:1::20]/overview.html
938
939 When this style is used, the `-g` option must be given to stop curl from
940 interpreting the square brackets as special globbing characters. Link local
941 and site local addresses including a scope identifier, such as `fe80::1234%1`,
942 may also be used, but the scope portion must be numeric or match an existing
943 network interface on Linux and the percent character must be URL escaped. The
944 previous example in an SFTP URL might look like:
945
946 sftp://[fe80::1234%251]/
947
948 IPv6 addresses provided other than in URLs (e.g. to the `--proxy`,
949 `--interface` or `--ftp-port` options) should not be URL encoded.
950
951 ## Metalink
952
953 Curl supports Metalink (both version 3 and 4 (RFC 5854) are supported), a way
954 to list multiple URIs and hashes for a file. Curl will make use of the mirrors
955 listed within for failover if there are errors (such as the file or server not
956 being available). It will also verify the hash of the file after the download
957 completes. The Metalink file itself is downloaded and processed in memory and
958 not stored in the local file system.
959
960 Example to use a remote Metalink file:
961
962 curl --metalink http://www.example.com/example.metalink
963
964 To use a Metalink file in the local file system, use FILE protocol
965 (`file://`):
966
967 curl --metalink file://example.metalink
968
969 Please note that if FILE protocol is disabled, there is no way to use a local
970 Metalink file at the time of this writing. Also note that if `--metalink` and
971 `--include` are used together, `--include` will be ignored. This is because
972 including headers in the response will break Metalink parser and if the
973 headers are included in the file described in Metalink file, hash check will
974 fail.
975
976 ## Mailing Lists
977
978 For your convenience, we have several open mailing lists to discuss curl, its
979 development and things relevant to this. Get all info at
980 https://curl.haxx.se/mail/.
981
982 Please direct curl questions, feature requests and trouble reports to one of
983 these mailing lists instead of mailing any individual.
984
985 Available lists include:
986
987 ### curl-users
988
989 Users of the command line tool. How to use it, what doesn't work, new
990 features, related tools, questions, news, installations, compilations,
991 running, porting etc.
992
993 ### curl-library
994
995 Developers using or developing libcurl. Bugs, extensions, improvements.
996
997 ### curl-announce
998
999 Low-traffic. Only receives announcements of new public versions. At worst,
1000 that makes something like one or two mails per month, but usually only one
1001 mail every second month.
1002
1003 ### curl-and-php
1004
1005 Using the curl functions in PHP. Everything curl with a PHP angle. Or PHP with
1006 a curl angle.
1007
1008 ### curl-and-python
1009
1010 Python hackers using curl with or without the python binding pycurl.
1011