curl.1

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

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.TH curl 1 "21 Sep 2007" "Curl 7.17.1" "Curl Manual"
.SH NAME
curl \- transfer a URL
.SH SYNOPSIS
.B curl [options]
.I [URL...]
.SH DESCRIPTION
.B curl
is a tool to transfer data from or to a server, using one of the supported
protocols (HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP or
FILE).  The command is designed to work without user interaction.

curl offers a busload of useful tricks like proxy support, user
authentication, ftp upload, HTTP post, SSL connections, cookies, file transfer
resume and more. As you will see below, the number of features will make your
head spin!

curl is powered by libcurl for all transfer-related features. See
.BR libcurl (3)
for details.
.SH URL
The URL syntax is protocol dependent. You'll find a detailed description in
RFC 3986.

You can specify multiple URLs or parts of URLs by writing part sets within
braces as in:

 http://site.{one,two,three}.com

or you can get sequences of alphanumeric series by using [] as in:

 ftp://ftp.numericals.com/file[1-100].txt
 ftp://ftp.numericals.com/file[001-100].txt    (with leading zeros)
 ftp://ftp.letters.com/file[a-z].txt

No nesting of the sequences is supported at the moment, but you can use
several ones next to each other:

 http://any.org/archive[1996-1999]/vol[1-4]/part{a,b,c}.html

You can specify any amount of URLs on the command line. They will be fetched
in a sequential manner in the specified order.

Since curl 7.15.1 you can also specify step counter for the ranges, so that
you can get every Nth number or letter:

 http://www.numericals.com/file[1-100:10].txt
 http://www.letters.com/file[a-z:2].txt

If you specify URL without protocol:// prefix, curl will attempt to guess what
protocol you might want. It will then default to HTTP but try other protocols
based on often-used host name prefixes. For example, for host names starting
with "ftp." curl will assume you want to speak FTP.

Curl will attempt to re-use connections for multiple file transfers, so that
getting many files from the same server will not do multiple connects /
handshakes. This improves speed. Of course this is only done on files
specified on a single command line and cannot be used between separate curl
invokes.
.SH "PROGRESS METER"
curl normally displays a progress meter during operations, indicating amount
of transfered data, transfer speeds and estimated time left etc.

However, since curl displays data to the terminal by default, if you invoke
curl to do an operation and it is about to write data to the terminal, it
\fIdisables\fP the progress meter as otherwise it would mess up the output
mixing progress meter and response data.

If you want a progress meter for HTTP POST or PUT requests, you need to
redirect the response output to a file, using shell redirect (>), -o [file] or
similar.

It is not the same case for FTP upload as that operation is not spitting out
any response data to the terminal.

If you prefer a progress "bar" instead of the regular meter, \fI-#\fP is your
friend.
.SH OPTIONS
.IP "-a/--append"
(FTP) When used in an FTP upload, this will tell curl to append to the target
file instead of overwriting it. If the file doesn't exist, it will be created.

If this option is used twice, the second one will disable append mode again.
.IP "-A/--user-agent <agent string>"
(HTTP) Specify the User-Agent string to send to the HTTP server. Some badly
done CGIs fail if this field isn't set to "Mozilla/4.0". To encode blanks in
the string, surround the string with single quote marks. This can also be set
with the \fI-H/--header\fP option of course.

If this option is set more than once, the last one will be the one that's
used.
.IP "--anyauth"
(HTTP) Tells curl to figure out authentication method by itself, and use the
most secure one the remote site claims it supports. This is done by first
doing a request and checking the response-headers, thus inducing an extra
network round-trip. This is used instead of setting a specific authentication
method, which you can do with \fI--basic\fP, \fI--digest\fP, \fI--ntlm\fP, and
\fI--negotiate\fP.

Note that using --anyauth is not recommended if you do uploads from stdin,
since it may require data to be sent twice and then the client must be able to
rewind. If the need should arise when uploading from stdin, the upload
operation will fail.

If this option is used several times, the following occurrences make no
difference.
.IP "-b/--cookie <name=data>"
(HTTP)
Pass the data to the HTTP server as a cookie. It is supposedly the
data previously received from the server in a "Set-Cookie:" line.
The data should be in the format "NAME1=VALUE1; NAME2=VALUE2".

If no '=' letter is used in the line, it is treated as a filename to use to
read previously stored cookie lines from, which should be used in this session
if they match. Using this method also activates the "cookie parser" which will
make curl record incoming cookies too, which may be handy if you're using this
in combination with the \fI-L/--location\fP option. The file format of the
file to read cookies from should be plain HTTP headers or the Netscape/Mozilla
cookie file format.

\fBNOTE\fP that the file specified with \fI-b/--cookie\fP is only used as
input. No cookies will be stored in the file. To store cookies, use the
\fI-c/--cookie-jar\fP option or you could even save the HTTP headers to a file
using \fI-D/--dump-header\fP!

If this option is set more than once, the last one will be the one that's
used.
.IP "-B/--use-ascii"
Enable ASCII transfer when using FTP or LDAP. For FTP, this can also be
enforced by using an URL that ends with ";type=A". This option causes data
sent to stdout to be in text mode for win32 systems.

If this option is used twice, the second one will disable ASCII usage.
.IP "--basic"
(HTTP) Tells curl to use HTTP Basic authentication. This is the default and
this option is usually pointless, unless you use it to override a previously
set option that sets a different authentication method (such as \fI--ntlm\fP,
\fI--digest\fP and \fI--negotiate\fP).

If this option is used several times, the following occurrences make no
difference.
.IP "--ciphers <list of ciphers>"
(SSL) Specifies which ciphers to use in the connection. The list of ciphers
must be using valid ciphers. Read up on SSL cipher list details on this URL:
\fIhttp://www.openssl.org/docs/apps/ciphers.html\fP

NSS ciphers are done differently than OpenSSL and GnuTLS. The full list of
NSS ciphers is in the NSSCipherSuite entry at this URL:
\fIhttp://directory.fedora.redhat.com/docs/mod_nss.html#Directives\fP

If this option is used several times, the last one will override the others.
.IP "--compressed"
(HTTP) Request a compressed response using one of the algorithms libcurl
supports, and return the uncompressed document.  If this option is used and
the server sends an unsupported encoding, Curl will report an error.

If this option is used several times, each occurrence will toggle it on/off.
.IP "--connect-timeout <seconds>"
Maximum time in seconds that you allow the connection to the server to take.
This only limits the connection phase, once curl has connected this option is
of no more use. See also the \fI-m/--max-time\fP option.

If this option is used several times, the last one will be used.
.IP "-c/--cookie-jar <file name>"
Specify to which file you want curl to write all cookies after a completed
operation. Curl writes all cookies previously read from a specified file as
well as all cookies received from remote server(s). If no cookies are known,
no file will be written. The file will be written using the Netscape cookie
file format. If you set the file name to a single dash, "-", the cookies will
be written to stdout.

.B NOTE
If the cookie jar can't be created or written to, the whole curl operation
won't fail or even report an error clearly. Using -v will get a warning
displayed, but that is the only visible feedback you get about this possibly
lethal situation.

If this option is used several times, the last specified file name will be
used.
.IP "-C/--continue-at <offset>"
Continue/Resume a previous file transfer at the given offset. The given offset
is the exact number of bytes that will be skipped counted from the beginning
of the source file before it is transferred to the destination.  If used with
uploads, the ftp server command SIZE will not be used by curl.

Use "-C -" to tell curl to automatically find out where/how to resume the
transfer. It then uses the given output/input files to figure that out.

If this option is used several times, the last one will be used.
.IP "--create-dirs"
When used in conjunction with the -o option, curl will create the necessary
local directory hierarchy as needed. This option creates the dirs mentioned
with the -o option, nothing else. If the -o file name uses no dir or if the
dirs it mentions already exist, no dir will be created.

To create remote directories when using FTP or SFTP, try 
\fI--ftp-create-dirs\fP.
.IP "--crlf"
(FTP) Convert LF to CRLF in upload. Useful for MVS (OS/390).

If this option is used several times, the following occurrences make no
difference.
.IP "-d/--data <data>"
(HTTP) Sends the specified data in a POST request to the HTTP server, in a way
that can emulate as if a user has filled in a HTML form and pressed the submit
button. Note that the data is sent exactly as specified with no extra
processing (with all newlines cut off).  The data is expected to be
\&"url-encoded". This will cause curl to pass the data to the server using the
content-type application/x-www-form-urlencoded. Compare to \fI-F/--form\fP. If
this option is used more than once on the same command line, the data pieces
specified will be merged together with a separating &-letter. Thus, using '-d
name=daniel -d skill=lousy' would generate a post chunk that looks like
\&'name=daniel&skill=lousy'.

If you start the data with the letter @, the rest should be a file name to
read the data from, or - if you want curl to read the data from stdin.  The
contents of the file must already be url-encoded. Multiple files can also be
specified. Posting data from a file named 'foobar' would thus be done with
\fI--data\fP @foobar".

To post data purely binary, you should instead use the \fI--data-binary\fP
option.

\fI-d/--data\fP is the same as \fI--data-ascii\fP.

If this option is used several times, the ones following the first will
append data.
.IP "--data-ascii <data>"
(HTTP) This is an alias for the \fI-d/--data\fP option.

If this option is used several times, the ones following the first will
append data.
.IP "--data-binary <data>"
(HTTP) This posts data in a similar manner as \fI--data-ascii\fP does,
although when using this option the entire context of the posted data is kept
as-is. If you want to post a binary file without the strip-newlines feature of
the \fI--data-ascii\fP option, this is for you.

If this option is used several times, the ones following the first will
append data.
.IP "--digest"
(HTTP) Enables HTTP Digest authentication. This is a authentication that
prevents the password from being sent over the wire in clear text. Use this in
combination with the normal \fI-u/--user\fP option to set user name and
password. See also \fI--ntlm\fP, \fI--negotiate\fP and \fI--anyauth\fP for
related options.

If this option is used several times, the following occurrences make no
difference.
.IP "--disable-eprt"
(FTP) Tell curl to disable the use of the EPRT and LPRT commands when doing
active FTP transfers. Curl will normally always first attempt to use EPRT,
then LPRT before using PORT, but with this option, it will use PORT right
away. EPRT and LPRT are extensions to the original FTP protocol, may not work
on all servers but enable more functionality in a better way than the
traditional PORT command.

If this option is used several times, each occurrence will toggle this on/off.
.IP "--disable-epsv"
(FTP) Tell curl to disable the use of the EPSV command when doing passive FTP
transfers. Curl will normally always first attempt to use EPSV before PASV,
but with this option, it will not try using EPSV.

If this option is used several times, each occurrence will toggle this on/off.
.IP "-D/--dump-header <file>"
Write the protocol headers to the specified file.

This option is handy to use when you want to store the headers that a HTTP
site sends to you. Cookies from the headers could then be read in a second
curl invoke by using the \fI-b/--cookie\fP option! The \fI-c/--cookie-jar\fP
option is however a better way to store cookies.

When used on FTP, the ftp server response lines are considered being "headers"
and thus are saved there.