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BUGS
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BUGS
Curl has grown substantially from that day, several years ago, when I
started fiddling with it. When I write this, there are 16500 lines of source
code, and by the time you read this it has probably grown even more.
Of course there are lots of bugs left. And lots of misfeatures.
To help us make curl the stable and solid product we want it to be, we need
bug reports and bug fixes. If you can't fix a bug yourself and submit a fix
for it, try to report an as detailed report as possible to the curl mailing
list to allow one of us to have a go at a solution. You should also post
your bug/problem at curl's bug tracking system over at
http://sourceforge.net/bugs/?group_id=976
When reporting a bug, you should include information that will help us
understand what's wrong, what's expected and how to repeat it. You therefore
need to supply your operating system's name and version number (uname -a
under a unix is fine), what version of curl you're using (curl -v is fine),
what URL you were working with and anything else you think matters.
If curl crashed, causing a core dump (in unix), there is hardly any use to
send that huge file to anyone of us. Unless we have an exact same system
setup as you, we can't do much with it. What we instead ask of you is to get
a stack trace and send that (much smaller) output to us instead!
The address and how to subscribe to the mailing list is detailed in the
README.curl file.
HOW TO GET A STACK TRACE with a common unix debugger
====================================================
First, you must make sure that you compile all sources with -g and that you
don't 'strip' the final executable.
Run the program until it bangs.
Run your debugger on the core file, like '<debugger> curl core'. <debugger>
should be replaced with the name of your debugger, in most cases that will
be 'gdb', but 'dbx' and others also occur.
When the debugger has finished loading the core file and presents you a
prompt, you can give the compiler instructions. Enter 'where' (without the
quotes) and press return.
The list that is presented is the stack trace. If everything worked, it is
supposed to contain the chain of functions that were called when curl
crashed.

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CONTRIBUTE
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CONTRIBUTE
To Think About When Contributing Source Code
This document is intended to offer some guidelines that can be useful to
keep in mind when you decide to write a contribution to the project. This
concerns new features as well as corrections to existing flaws or bugs.
Naming
Try using a non-confusing naming scheme for your new functions and variable
names. It doesn't necessarily have to mean that you should use the same as
in other places of the code, just that the names should be logical,
understandable and be named according to what they're used for.
Indenting
Please try using the same indenting levels and bracing method as all the
other code already does. It makes the source code a lot easier to follow if
all of it is written using the same style. I don't ask you to like it, I
just ask you to follow the tradition! ;-)
Commenting
Comment your source code extensively. I don't see myself as a very good
source commenter, but I try to become one. Commented code is quality code
and enables future modifications much more. Uncommented code much more risk
being completely replaced when someone wants to extend things, since other
persons' source code can get quite hard to read.
General Style
Keep your functions small. If they're small you avoid a lot of mistakes and
you don't accidentally mix up variables.
Non-clobbering All Over
When you write new functionality or fix bugs, it is important that you
don't fiddle all over the source files and functions. Remember that it is
likely that other people have done changes in the same source files as you
have and possibly even in the same functions. If you bring completely new
functionality, try writing it in a new source file. If you fix bugs, try to
fix one bug at a time and send them as separate patches.
Separate Patches Doing Different Things
It is annoying when you get a huge patch from someone that is said to fix 511
odd problems, but discussions and opinions don't agree with 510 of them - or
509 of them were already fixed in a different way. Then the patcher needs to
extract the single interesting patch from somewhere within the huge pile of
source, and that gives a lot of extra work. Preferably, all fixes that
correct different problems should be in their own patch with an attached
description exactly what they correct so that all patches can be selectively
applied by the maintainer or other interested parties.
Document
Writing docs is dead boring and one of the big problems with many open
source projects. Someone's gotta do it. It makes it a lot easier if you
submit a small description of your fix or your new features with every
contribution so that it can be swiftly added to the package documentation.
Write Access to CVS Repository
If you are a frequent contributor, or have another good reason, you can of
course get write access to the CVS repository and then you'll be able to
check-in all your changes straight into the CVS tree instead of sending all
changes by mail as patches. Just ask if this is what you'd want.

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FAQ
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FAQ
Problems connecting to SSL servers.
===================================
It took a very long time before I could sort out why curl had problems
to connect to certain SSL servers when using SSLeay or OpenSSL v0.9+.
The error sometimes showed up similar to:
16570:error:1407D071:SSL routines:SSL2_READ:bad mac decode:s2_pkt.c:233:
It turned out to be because many older SSL servers don't deal with SSLv3
requests properly. To correct this problem, tell curl to select SSLv2 from
the command line (-2/--sslv2).
I have also seen examples where the remote server didn't like the SSLv2
request and instead you had to force curl to use SSLv3 with -3/--sslv3.
Does curl support resume?
=========================
Yes. Both ways on FTP, download ways on HTTP.
Is libcurl thread safe?
=======================
Yes, as far as curl's own code goes. It does use system calls that often
aren't thread safe in most environments, such as gethostbyname().
I am very interested in once and for all getting some kind of report or
README file from those who have used libcurl in a threaded environment,
since I haven't and I get this question more and more frequently!
Why doesn't my posting using -F work?
=====================================
You can't simply use -F or -d at your choice. The web server that will
receive your post assumes one of the formats. If the form you're trying to
"fake" sets the type to 'multipart/form-data', than and only then you must
use the -F type. In all the most common cases, you should use -d which then
causes a posting with the type 'application/x-www-form-urlencoded'.
Does curl support custom FTP commands?
======================================
Yes it does, you can tell curl to perform optional commands both before
and/or after a file transfer. Study the -Q/--quote option.
Since curl is used for file transfers, you don't use curl to just perform
ftp commands without transfering anything. Therefore you must always specify
a URL to transfer to/from even when doing custom FTP commands.
Does curl work with other SSL libraries?
========================================
Curl has been written to use OpenSSL, although I doubt there would be much
problems using a different library. I just don't know any other free one and
that has limited my possibilities to develop against anything else.
If anyone does "port" curl to use a commercial SSL library, I am of course
very interested in getting the patch!
configre doesn't find OpenSSL even when it is installed
=======================================================
Platforms: Solaris (native cc compiler) and HPUX (native cc compiler)
When configuring curl, I specify --with-ssl. OpenSSL is installed in
/usr/local/ssl Configure reports SSL in /usr/local/ssl, but fails to find
CRYPTO_lock in -lcrypto
Cause: The cc for this test places the -L/usr/local/ssl/lib AFTER -lcrypto,
so ld can't find the library. This is due to a bug in the GNU autoconf tool.
Workaround: Specifying "LDFLAGS=-L/usr/local/ssl/lib" in front of ./configure
places the -L/usr/local/ssl/lib early enough in the command line to make
things work
Submitted by: Bob Allison <allisonb@users.sourceforge.net>

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FEATURES
Misc
- full URL syntax
- custom maximum download time
- custom least download speed acceptable
- custom output result after completion
- multiple URLs
- guesses protocol from host name unless specified
- uses .netrc
- progress bar/time specs while downloading
- PROXY environment variables support
- config file support
- compiles on win32
HTTP
- GET
- PUT
- HEAD
- POST
- multipart POST
- authentication
- resume
- follow redirects
- custom HTTP request
- cookie get/send
- understands the netscape cookie file
- custom headers (that can replace internally generated headers)
- custom user-agent string
- custom referer string
- range
- proxy authentication
- time conditions
- via http-proxy
HTTPS (*1)
- (all the HTTP features)
- using certificates
- via http-proxy
FTP
- download
- authentication
- PORT or PASV
- single file size information (compare to HTTP HEAD)
- 'type=' URL support
- dir listing
- dir listing names-only
- upload
- upload append
- upload via http-proxy as HTTP PUT
- download resume
- upload resume
- QUOT commands (before and/or after the transfer)
- simple "range" support
- via http-proxy
TELNET
- connection negotiation
- stdin/stdout I/O
LDAP (*2)
- full LDAP URL support
DICT
- extended DICT URL support
GOPHER
- GET
- via http-proxy
FILE
- URL support
*1 = requires OpenSSL
*2 = requires OpenLDAP

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INSTALL
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How To Compile
Curl has been compiled and built on numerous different operating systems. The
way to proceed is mainly divided in two different ways: the unix way or the
windows way.
If you're using Windows (95, 98, NT) or OS/2, you should continue reading from
the Win32 header below. All other systems should be capable of being installed
as described in the the UNIX header.
PORTS
=====
Just to show off, this is a probably incomplete list of known hardware and
operating systems that curl has been compiled for:
- Ultrix
- SINIX-Z v5
Alpha DEC OSF 4
HP-PA HP-UX 10.X 11.X
MIPS IRIX 6.2, 6.5
Power AIX 4.2, 4.3.1
PowerPC Darwin 1.0
PowerPC Mac OS X
Sparc Solaris 2.4, 2.5, 2.5.1, 2.6, 7
Sparc SunOS 4.1.*
i386 BeOS
i386 FreeBSD
i386 Linux 1.3, 2.0, 2.2
i386 NetBSD
i386 OS/2
i386 OpenBSD
i386 Solaris 2.7
i386 Windows 95, 98, NT
m68k AmigaOS 3
m68k OpenBSD
UNIX
====
The configure script *always* tries to find a working SSL library unless
explicitly told not to. If you have OpenSSL installed in the default
search path for your compiler/linker, you don't need to do anything
special.
If you have OpenSSL installed in /usr/local/ssl, you can run configure
like:
./configure --with-ssl
If you have OpenSSL installed somewhere else (for example, /opt/OpenSSL,)
you can run configure like this:
./configure --with-ssl=/opt/OpenSSL
If you insist on forcing a build *without* SSL support, even though you may
have it installed in your system, you can run configure like this:
./configure --without-ssl
If you have OpenSSL installed, but with the libraries in one place and the
header files somewhere else, you'll have to set the LDFLAGS and CPPFLAGS
environment variables prior to running configure. Something like this
should work:
(with the Bourne shell and its clones):
CPPFLAGS="-I/path/to/ssl/include" LDFLAGS="-L/path/to/ssl/lib" \
./configure
(with csh, tcsh and their clones):
env CPPFLAGS="-I/path/to/ssl/include" LDFLAGS="-L/path/to/ssl/lib" \
./configure
If your SSL library was compiled with rsaref (usually for use in
the United States), you may also need to set:
LIBS=-lRSAglue -lrsaref
(from Doug Kaufman <dkaufman@rahul.net>)
Without SSL support, just run:
./configure
Then run:
make
Use the executable `curl` in src/ directory.
'make install' copies the curl file to /usr/local/bin/ (or $prefix/bin
if you used the --prefix option to configure) and copies the curl.1
man page to a suitable place too.
KNOWN PROBLEMS
If you happen to have autoconf installed, but a version older than
2.12 you will get into trouble. Then you can still build curl by
issuing these commands: (from Ralph Beckmann <rabe@uni-paderborn.de>)
./configure [...]
cd lib; make; cd ..
cd src; make; cd ..
cp src/curl elsewhere/bin/
OPTIONS
Remember, to force configure to use the standard cc compiler if both
cc and gcc are present, run configure like
CC=cc ./configure
or
env Cc=cc ./configure
Win32
=====
Without SSL:
MingW32 (GCC-2.95) style
------------------------
Run the 'mingw32.bat' file to get the proper environment variables
set, then run 'make -f Makefile.m32' in the lib/ dir and then
'make -f Makefile.m32' in the src/ dir.
If you have any problems linking libraries or finding header files,
be sure to look at the provided "Makefile.m32" files for the proper
paths, and adjust as necessary.
Cygwin style
------------
Almost identical to the unix installation. Run the configure script
in the curl root with 'sh configure'. Make sure you have the sh
executable in /bin/ or you'll see the configure fail towards the
end.
Run 'make'
Microsoft command line style
----------------------------
Run the 'vcvars32.bat' file to get the proper environment variables
set, then run 'nmake -f Makefile.vc6' in the lib/ dir and then
'nmake -f Makefile.vc6' in the src/ dir.
IDE-style
-------------------------
If you use VC++, Borland or similar compilers. Include all lib source
files in a static lib "project" (all .c and .h files that is).
(you should name it libcurl or similar)
Make the sources in the src/ drawer be a "win32 console application"
project. Name it curl.
With VC++, add 'wsock32.lib' to the link libs when you build curl!
Borland seems to do that itself magically. Of course you have to
make sure it links with the libcurl too!
For VC++ 6, there's an included Makefile.vc6 that should be possible
to use out-of-the-box.
Microsoft note: add /Zm200 to the compiler options, as the hugehelp.c
won't compile otherwise due to "too long puts string" or something
like that!
With SSL:
MingW32 (GCC-2.95) style
------------------------
Run the 'mingw32.bat' file to get the proper environment variables
set, then run 'make -f Makefile.m32 SSL=1' in the lib/ dir and then
'make -f Makefile.m32 SSL=1' in the src/ dir.
If you have any problems linking libraries or finding header files,
be sure to look at the provided "Makefile.m32" files for the proper
paths, and adjust as necessary.
Cygwin style
------------
Haven't done, nor got any reports on how to do. It should although be
identical to the unix setup for the same purpose. See above.
Microsoft command line style
----------------------------
Run the 'vcvars32.bat' file to get the proper environment variables
set, then run 'nmake -f Makefile.vc6 release-ssl' in the lib/ dir and
then 'nmake -f Makefile.vc6' in the src/ dir.
Microsoft / Borland style
-------------------------
If you have OpenSSL, and want curl to take advantage of it, edit your
project properties to use the SSL include path, link with the SSL libs
and define the USE_SSLEAY symbol.
IBM OS/2
========
Building under OS/2 is not much different from building under unix.
You need:
- emx 0.9d
- GNU make
- GNU patch
- ksh
- GNU bison
- GNU file utilities
- GNU sed
- autoconf 2.13
If you want to build with OpenSSL or OpenLDAP support, you'll need to
download those libraries, too. Dirk Ohme has done some work to port SSL
libraries under OS/2, but it looks like he doesn't care about emx. You'll
find his patches on: http://come.to/Dirk.Ohme
If during the linking you get an error about _errno being an undefined
symbol referenced from the text segment, you need to add -D__ST_MT_ERRNO__
in your definitions.
If everything seems to work fine but there's no curl.exe, you need to add
-Zexe to your linker flags.
If you're getting huge binaries, probably your makefiles have the -g in
CFLAGS.
OpenSSL
=======
You'll find OpenSSL information at:
http://www.openssl.org
MingW32/Cygwin
==============
You'll find MingW32 and Cygwin information at:
http://www.xraylith.wisc.edu/~khan/software/gnu-win32/index.html
OpenLDAP
========
You'll find OpenLDAP information at:
http://www.openldap.org
You need to install it with shared libraries, which is enabled when running
the ldap configure script with "--enable-shared". With my linux 2.0.36
kernel I also had to disable using threads (with --without-threads),
because the configure script couldn't figure out my system.

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INTERNALS
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INTERNALS
The project is kind of split in two. The library and the client. The client
part uses the library, but the library is meant to be designed to allow other
applications to use it.
Thus, the largest amount of code and complexity is in the library part.
Windows vs Unix
===============
There are a few differences in how to program curl the unix way compared to
the Windows way. The four most notable details are:
1. Different function names for close(), read(), write()
2. Windows requires a couple of init calls
3. The file descriptors for network communication and file operations are
not easily interchangable as in unix
4. When writing data to stdout, Windows makes end-of-lines the DOS way, thus
destroying binary data, although you do want that conversion if it is
text coming through... (sigh)
In curl, (1) and (2) are done with defines and macros, so that the source
looks the same at all places except for the header file that defines them.
(3) is simply avoided by not trying any funny tricks on file descriptors.
(4) is left alone, giving windows users problems when they pipe binary data
through stdout...
Inside the source code, I do make an effort to avoid '#ifdef WIN32'. All
conditionals that deal with features *should* instead be in the format
'#ifdef HAVE_THAT_WEIRD_FUNCTION'. Since Windows can't run configure scripts,
I maintain two config-win32.h files (one in / and one in src/) that are
supposed to look exactly as a config.h file would have looked like on a
Windows machine!
Library
=======
There is a few entry points to the library, namely each publicly defined
function that libcurl offers to applications. All of those functions are
rather small and easy-to-follow, accept the one single and do-it-all named
curl_urlget() (entry point in lib/url.c).
curl_urlget() takes a variable amount of arguments, and they must all be
passed in pairs, the parameter-ID and the parameter-value. The list of
arguments must be ended with a end-of-arguments parameter-ID.
The function then continues to analyze the URL, get the different components
and connects to the remote host. This may involve using a proxy and/or using
SSL. The GetHost() function in lib/hostip.c is used for looking up host
names.
When connected, the proper function is called. The functions are named after
the protocols they handle. ftp(), http(), dict(), etc. They all reside in
their respective files (ftp.c, http.c and dict.c).
The protocol-specific functions deal with protocol-specific negotiations and
setup. They have access to the sendf() (from lib/sendf.c) function to send
printf-style formatted data to the remote host and when they're ready to make
the actual file transfer they call the Transfer() function (in
lib/download.c) to do the transfer. All printf()-style functions use the
supplied clones in lib/mprintf.c.
While transfering, the progress functions in lib/progress.c are called at a
frequent interval. The speedcheck functions in lib/speedcheck.c are also used
to verify that the transfer is as fast as required.
When the operation is done, the writeout() function in lib/writeout.c may be
called to report about the operation as specified previously in the arguments
to curl_urlget().
HTTP(S)
HTTP offers a lot and is the protocol in curl that uses the most lines of
code. There is a special file (lib/formdata.c) that offers all the multipart
post functions.
base64-functions for user+password stuff is in (lib/base64.c) and all
functions for parsing and sending cookies are found in
(lib/cookie.c).
HTTPS uses in almost every means the same procedure as HTTP, with only two
exceptions: the connect procedure is different and the function used
FTP
The if2ip() function can be used for getting the IP number of a specified
network interface, and it resides in lib/if2ip.c
TELNET
Telnet is implemented in lib/telnet.c.
FILE
The file:// protocol is dealt with in lib/file.c.
LDAP
Everything LDAP is in lib/ldap.c.
GENERAL
URL encoding and decoding, called escaping and unescaping in the source code,
is found in lib/escape.c.
While transfering data in Transfer() a few functions might get
used. get_date() in lib/getdate.c is for HTTP date comparisons.
lib/getenv.c is for reading environment variables in a neat platform
independent way. That's used in the client, but also in lib/url.c when
checking the PROXY variables.
lib/netrc.c keeps the .netrc parser
lib/timeval.c features replacement functions for systems that don't have
A function named curl_version() that returns the full curl version string is
found in lib/version.c.
Client
======
main() resides in src/main.c together with most of the client
code. src/hugehelp.c is automatically generated by the mkhelp.pl perl script
to display the complete "manual" and the src/urlglob.c file holds the
functions used for the multiple-URL support.
The client mostly mess around to setup its config struct properly, then it
calls the curl_urlget() function in the library and when it gets back control
it checks status and exits.

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LATEST VERSION
You always find news about what's going on as well as the latest versions
from the curl web pages, located at:
http://curl.haxx.nu
SIMPLE USAGE
Get the main page from netscape's web-server:
curl http://www.netscape.com/
Get the root README file from funet's ftp-server:
curl ftp://ftp.funet.fi/README
Get a gopher document from funet's gopher server:
curl gopher://gopher.funet.fi
Get a web page from a server using port 8000:
curl http://www.weirdserver.com:8000/
Get a list of the root directory of an FTP site:
curl ftp://ftp.fts.frontec.se/
Get the definition of curl from a dictionary:
curl dict://dict.org/m:curl
DOWNLOAD TO A FILE
Get a web page and store in a local file:
curl -o thatpage.html http://www.netscape.com/
Get a web page and store in a local file, make the local file get the name
of the remote document (if no file name part is specified in the URL, this
will fail):
curl -O http://www.netscape.com/index.html
USING PASSWORDS
FTP
To ftp files using name+passwd, include them in the URL like:
curl ftp://name:passwd@machine.domain:port/full/path/to/file
or specify them with the -u flag like
curl -u name:passwd ftp://machine.domain:port/full/path/to/file
HTTP
The HTTP URL doesn't support user and password in the URL string. Curl
does support that anyway to provide a ftp-style interface and thus you can
pick a file like:
curl http://name:passwd@machine.domain/full/path/to/file
or specify user and password separately like in
curl -u name:passwd http://machine.domain/full/path/to/file
NOTE! Since HTTP URLs don't support user and password, you can't use that
style when using Curl via a proxy. You _must_ use the -u style fetch
during such circumstances.
HTTPS
Probably most commonly used with private certificates, as explained below.
GOPHER
Curl features no password support for gopher.
PROXY
Get an ftp file using a proxy named my-proxy that uses port 888:
curl -x my-proxy:888 ftp://ftp.leachsite.com/README
Get a file from a HTTP server that requires user and password, using the
same proxy as above:
curl -u user:passwd -x my-proxy:888 http://www.get.this/
Some proxies require special authentication. Specify by using -U as above:
curl -U user:passwd -x my-proxy:888 http://www.get.this/
See also the environment variables Curl support that offer further proxy
control.
RANGES
With HTTP 1.1 byte-ranges were introduced. Using this, a client can request
to get only one or more subparts of a specified document. Curl supports
this with the -r flag.
Get the first 100 bytes of a document:
curl -r 0-99 http://www.get.this/
Get the last 500 bytes of a document:
curl -r -500 http://www.get.this/
Curl also supports simple ranges for FTP files as well. Then you can only
specify start and stop position.
Get the first 100 bytes of a document using FTP:
curl -r 0-99 ftp://www.get.this/README
UPLOADING
FTP
Upload all data on stdin to a specified ftp site:
curl -t ftp://ftp.upload.com/myfile
Upload data from a specified file, login with user and password:
curl -T uploadfile -u user:passwd ftp://ftp.upload.com/myfile
Upload a local file to the remote site, and use the local file name remote
too:
curl -T uploadfile -u user:passwd ftp://ftp.upload.com/
Upload a local file to get appended to the remote file using ftp:
curl -T localfile -a ftp://ftp.upload.com/remotefile
NOTE: Curl does not support ftp upload through a proxy! The reason for this
is simply that proxies are seldomly configured to allow this and that no
author has supplied code that makes it possible!
HTTP
Upload all data on stdin to a specified http site:
curl -t http://www.upload.com/myfile
Note that the http server must've been configured to accept PUT before this
can be done successfully.
For other ways to do http data upload, see the POST section below.
VERBOSE / DEBUG
If curl fails where it isn't supposed to, if the servers don't let you
in, if you can't understand the responses: use the -v flag to get VERBOSE
fetching. Curl will output lots of info and all data it sends and
receives in order to let the user see all client-server interaction.
curl -v ftp://ftp.upload.com/
DETAILED INFORMATION
Different protocols provide different ways of getting detailed information
about specific files/documents. To get curl to show detailed information
about a single file, you should use -I/--head option. It displays all
available info on a single file for HTTP and FTP. The HTTP information is a
lot more extensive.
For HTTP, you can get the header information (the same as -I would show)
shown before the data by using -i/--include. Curl understands the
-D/--dump-header option when getting files from both FTP and HTTP, and it
will then store the headers in the specified file.
Store the HTTP headers in a separate file:
curl --dump-header headers.txt curl.haxx.nu
Note that headers stored in a separate file can be very useful at a later
time if you want curl to use cookies sent by the server. More about that in
the cookies section.
POST (HTTP)
It's easy to post data using curl. This is done using the -d <data>
option. The post data must be urlencoded.
Post a simple "name" and "phone" guestbook.
curl -d "name=Rafael%20Sagula&phone=3320780" \
http://www.where.com/guest.cgi
How to post a form with curl, lesson #1:
Dig out all the <input> tags in the form that you want to fill in. (There's
a perl program called formfind.pl on the curl site that helps with this).
If there's a "normal" post, you use -d to post. -d takes a full "post
string", which is in the format
<variable1>=<data1>&<variable2>=<data2>&...
The 'variable' names are the names set with "name=" in the <input> tags, and
the data is the contents you want to fill in for the inputs. The data *must*
be properly URL encoded. That means you replace space with + and that you
write weird letters with %XX where XX is the hexadecimal representation of
the letter's ASCII code.
Example:
(page located at http://www.formpost.com/getthis/
<form action="post.cgi" method="post">
<input name=user size=10>
<input name=pass type=password size=10>
<input name=id type=hidden value="blablabla">
<input name=ding value="submit">
</form>
We want to enter user 'foobar' with password '12345'.
To post to this, you enter a curl command line like:
curl -d "user=foobar&pass=12345&id=blablabla&dig=submit" (continues)
http://www.formpost.com/getthis/post.cgi
While -d uses the application/x-www-form-urlencoded mime-type, generally
understood by CGI's and similar, curl also supports the more capable
multipart/form-data type. This latter type supports things like file upload.
-F accepts parameters like -F "name=contents". If you want the contents to
be read from a file, use <@filename> as contents. When specifying a file,
you can also specify which content type the file is, by appending
';type=<mime type>' to the file name. You can also post contents of several
files in one field. So that the field name 'coolfiles' can be sent three
files with different content types in a manner similar to:
curl -F "coolfiles=@fil1.gif;type=image/gif,fil2.txt,fil3.html" \
http://www.post.com/postit.cgi
If content-type is not specified, curl will try to guess from the extension
(it only knows a few), or use the previously specified type (from an earlier
file if several files are specified in a list) or finally using the default
type 'text/plain'.
Emulate a fill-in form with -F. Let's say you fill in three fields in a
form. One field is a file name which to post, one field is your name and one
field is a file description. We want to post the file we have written named
"cooltext.txt". To let curl do the posting of this data instead of your
favourite browser, you have to check out the HTML of the form page to get to
know the names of the input fields. In our example, the input field names are
'file', 'yourname' and 'filedescription'.
curl -F "file=@cooltext.txt" -F "yourname=Daniel" \
-F "filedescription=Cool text file with cool text inside" \
http://www.post.com/postit.cgi
So, to send two files in one post you can do it in two ways:
1. Send multiple files in a single "field" with a single field name:
curl -F "pictures=@dog.gif,cat.gif"
2. Send two fields with two field names:
curl -F "docpicture=@dog.gif" -F "catpicture=@cat.gif"
REFERER
A HTTP request has the option to include information about which address
that referred to actual page, and curl allows the user to specify that
referrer to get specified on the command line. It is especially useful to
fool or trick stupid servers or CGI scripts that rely on that information
being available or contain certain data.
curl -e www.coolsite.com http://www.showme.com/
USER AGENT
A HTTP request has the option to include information about the browser
that generated the request. Curl allows it to be specified on the command
line. It is especially useful to fool or trick stupid servers or CGI
scripts that only accept certain browsers.
Example:
curl -A 'Mozilla/3.0 (Win95; I)' http://www.nationsbank.com/
Other common strings:
'Mozilla/3.0 (Win95; I)' Netscape Version 3 for Windows 95
'Mozilla/3.04 (Win95; U)' Netscape Version 3 for Windows 95
'Mozilla/2.02 (OS/2; U)' Netscape Version 2 for OS/2
'Mozilla/4.04 [en] (X11; U; AIX 4.2; Nav)' NS for AIX
'Mozilla/4.05 [en] (X11; U; Linux 2.0.32 i586)' NS for Linux
Note that Internet Explorer tries hard to be compatible in every way:
'Mozilla/4.0 (compatible; MSIE 4.01; Windows 95)' MSIE for W95
Mozilla is not the only possible User-Agent name:
'Konqueror/1.0' KDE File Manager desktop client
'Lynx/2.7.1 libwww-FM/2.14' Lynx command line browser
COOKIES
Cookies are generally used by web servers to keep state information at the
client's side. The server sets cookies by sending a response line in the
headers that looks like 'Set-Cookie: <data>' where the data part then
typically contains a set of NAME=VALUE pairs (separated by semicolons ';'
like "NAME1=VALUE1; NAME2=VALUE2;"). The server can also specify for what
path the "cookie" should be used for (by specifying "path=value"), when the
cookie should expire ("expire=DATE"), for what domain to use it
("domain=NAME") and if it should be used on secure connections only
("secure").
If you've received a page from a server that contains a header like:
Set-Cookie: sessionid=boo123; path="/foo";
it means the server wants that first pair passed on when we get anything in
a path beginning with "/foo".
Example, get a page that wants my name passed in a cookie:
curl -b "name=Daniel" www.sillypage.com
Curl also has the ability to use previously received cookies in following
sessions. If you get cookies from a server and store them in a file in a
manner similar to:
curl --dump-header headers www.example.com
... you can then in a second connect to that (or another) site, use the
cookies from the 'headers' file like:
curl -b headers www.example.com
Note that by specifying -b you enable the "cookie awareness" and with -L
you can make curl follow a location: (which often is used in combination
with cookies). So that if a site sends cookies and a location, you can
use a non-existing file to trig the cookie awareness like:
curl -L -b empty-file www.example.com
The file to read cookies from must be formatted using plain HTTP headers OR
as netscape's cookie file. Curl will determine what kind it is based on the
file contents.
PROGRESS METER
The progress meter exists to show a user that something actually is
happening. The different fields in the output have the following meaning:
% Total % Received % Xferd Average Speed Time Curr.
Dload Upload Total Current Left Speed
0 151M 0 38608 0 0 9406 0 4:41:43 0:00:04 4:41:39 9287
From left-to-right:
% - percentage completed of the whole transfer
Total - total size of the whole expected transfer
% - percentage completed of the download
Received - currently downloaded amount of bytes
% - percentage completed of the upload
Xferd - currently uploaded amount of bytes
Average Speed
Dload - the average transfer speed of the download
Average Speed
Upload - the average transfer speed of the upload
Time Total - expected time to complete the operation
Time Current - time passed since the invoke
Time Left - expected time left to completetion
Curr.Speed - the average transfer speed the last 5 seconds (the first
5 seconds of a transfer is based on less time of course.)
The -# option will display a totally different progress bar that doesn't
need much explanation!
SPEED LIMIT
Curl offers the user to set conditions regarding transfer speed that must
be met to let the transfer keep going. By using the switch -y and -Y you
can make curl abort transfers if the transfer speed doesn't exceed your
given lowest limit for a specified time.
To let curl abandon downloading this page if its slower than 3000 bytes per
second for 1 minute, run:
curl -y 3000 -Y 60 www.far-away-site.com
This can very well be used in combination with the overall time limit, so
that the above operatioin must be completed in whole within 30 minutes:
curl -m 1800 -y 3000 -Y 60 www.far-away-site.com
CONFIG FILE
Curl automatically tries to read the .curlrc file (or _curlrc file on win32
systems) from the user's home dir on startup. The config file should be
made up with normal command line switches. Comments can be used within the
file. If the first letter on a line is a '#'-letter the rest of the line
is treated as a comment.
Example, set default time out and proxy in a config file:
# We want a 30 minute timeout:
-m 1800
# ... and we use a proxy for all accesses:
-x proxy.our.domain.com:8080
White spaces ARE significant at the end of lines, but all white spaces
leading up to the first characters of each line are ignored.
Prevent curl from reading the default file by using -q as the first command
line parameter, like:
curl -q www.thatsite.com
Force curl to get and display a local help page in case it is invoked
without URL by making a config file similar to:
# default url to get
http://help.with.curl.com/curlhelp.html
You can specify another config file to be read by using the -K/--config
flag. If you set config file name to "-" it'll read the config from stdin,
which can be handy if you want to hide options from being visible in process
tables etc:
echo "-u user:passwd" | curl -K - http://that.secret.site.com
EXTRA HEADERS
When using curl in your own very special programs, you may end up needing
to pass on your own custom headers when getting a web page. You can do
this by using the -H flag.
Example, send the header "X-you-and-me: yes" to the server when getting a
page:
curl -H "X-you-and-me: yes" www.love.com
This can also be useful in case you want curl to send a different text in
a header than it normally does. The -H header you specify then replaces the
header curl would normally send.
FTP and PATH NAMES
Do note that when getting files with the ftp:// URL, the given path is
relative the directory you enter. To get the file 'README' from your home
directory at your ftp site, do:
curl ftp://user:passwd@my.site.com/README
But if you want the README file from the root directory of that very same
site, you need to specify the absolute file name:
curl ftp://user:passwd@my.site.com//README
(I.e with an extra slash in front of the file name.)
FTP and firewalls
The FTP protocol requires one of the involved parties to open a second
connction as soon as data is about to get transfered. There are two ways to
do this.
The default way for curl is to issue the PASV command which causes the
server to open another port and await another connection performed by the
client. This is good if the client is behind a firewall that don't allow
incoming connections.
curl ftp.download.com
If the server for example, is behind a firewall that don't allow connections
on other ports than 21 (or if it just doesn't support the PASV command), the
other way to do it is to use the PORT command and instruct the server to
connect to the client on the given (as parameters to the PORT command) IP
number and port.
The -P flag to curl allows for different options. Your machine may have
several IP-addresses and/or network interfaces and curl allows you to select
which of them to use. Default address can also be used:
curl -P - ftp.download.com
Download with PORT but use the IP address of our 'le0' interface:
curl -P le0 ftp.download.com
Download with PORT but use 192.168.0.10 as our IP address to use:
curl -P 192.168.0.10 ftp.download.com
HTTPS
Secure HTTP requires SSL libraries to be installed and used when curl is
built. If that is done, curl is capable of retrieving and posting documents
using the HTTPS procotol.
Example:
curl https://www.secure-site.com
Curl is also capable of using your personal certificates to get/post files
from sites that require valid certificates. The only drawback is that the
certificate needs to be in PEM-format. PEM is a standard and open format to
store certificates with, but it is not used by the most commonly used
browsers (Netscape and MSEI both use the so called PKCS#12 format). If you
want curl to use the certificates you use with your (favourite) browser, you
may need to download/compile a converter that can convert your browser's
formatted certificates to PEM formatted ones. This kind of converter is
included in recent versions of OpenSSL, and for older versions Dr Stephen
N. Henson has written a patch for SSLeay that adds this functionality. You
can get his patch (that requires an SSLeay installation) from his site at:
http://www.drh-consultancy.demon.co.uk/
Example on how to automatically retrieve a document using a certificate with
a personal password:
curl -E /path/to/cert.pem:password https://secure.site.com/
If you neglect to specify the password on the command line, you will be
prompted for the correct password before any data can be received.
Many older SSL-servers have problems with SSLv3 or TLS, that newer versions
of OpenSSL etc is using, therefore it is sometimes useful to specify what
SSL-version curl should use. Use -3 or -2 to specify that exact SSL version
to use:
curl -2 https://secure.site.com/
Otherwise, curl will first attempt to use v3 and then v2.
RESUMING FILE TRANSFERS
To continue a file transfer where it was previously aborted, curl supports
resume on http(s) downloads as well as ftp uploads and downloads.
Continue downloading a document:
curl -c -o file ftp://ftp.server.com/path/file
Continue uploading a document(*1):
curl -c -T file ftp://ftp.server.com/path/file
Continue downloading a document from a web server(*2):
curl -c -o file http://www.server.com/
(*1) = This requires that the ftp server supports the non-standard command
SIZE. If it doesn't, curl will say so.
(*2) = This requires that the wb server supports at least HTTP/1.1. If it
doesn't, curl will say so.
TIME CONDITIONS
HTTP allows a client to specify a time condition for the document it
requests. It is If-Modified-Since or If-Unmodified-Since. Curl allow you to
specify them with the -z/--time-cond flag.
For example, you can easily make a download that only gets performed if the
remote file is newer than a local copy. It would be made like:
curl -z local.html http://remote.server.com/remote.html
Or you can download a file only if the local file is newer than the remote
one. Do this by prepending the date string with a '-', as in:
curl -z -local.html http://remote.server.com/remote.html
You can specify a "free text" date as condition. Tell curl to only download
the file if it was updated since yesterday:
curl -z yesterday http://remote.server.com/remote.html
Curl will then accept a wide range of date formats. You always make the date
check the other way around by prepending it with a dash '-'.
DICT
For fun try
curl dict://dict.org/m:curl
curl dict://dict.org/d:heisenbug:jargon
curl dict://dict.org/d:daniel:web1913
Aliases for 'm' are 'match' and 'find', and aliases for 'd' are 'define'
and 'lookup'. For example,
curl dict://dict.org/find:curl
Commands that break the URL description of the RFC (but not the DICT
protocol) are
curl dict://dict.org/show:db
curl dict://dict.org/show:strat
Authentication is still missing (but this is not required by the RFC)
LDAP
If you have installed the OpenLDAP library, curl can take advantage of it
and offer ldap:// support.
LDAP is a complex thing and writing an LDAP query is not an easy task. I do
advice you to dig up the syntax description for that elsewhere, RFC 1959 if
no other place is better.
To show you an example, this is now I can get all people from my local LDAP
server that has a certain sub-domain in their email address:
curl -B "ldap://ldap.frontec.se/o=frontec??sub?mail=*sth.frontec.se"
If I want the same info in HTML format, I can get it by not using the -B
(enforce ASCII) flag.
ENVIRONMENT VARIABLES
Curl reads and understands the following environment variables:
HTTP_PROXY, HTTPS_PROXY, FTP_PROXY, GOPHER_PROXY
They should be set for protocol-specific proxies. General proxy should be
set with
ALL_PROXY
A comma-separated list of host names that shouldn't go through any proxy is
set in (only an asterisk, '*' matches all hosts)
NO_PROXY
If a tail substring of the domain-path for a host matches one of these
strings, transactions with that node will not be proxied.
The usage of the -x/--proxy flag overrides the environment variables.
NETRC
Unix introduced the .netrc concept a long time ago. It is a way for a user
to specify name and password for commonly visited ftp sites in a file so
that you don't have to type them in each time you visit those sites. You
realize this is a big security risk if someone else gets hold of your
passwords, so therefor most unix programs won't read this file unless it is
only readable by yourself (curl doesn't care though).
Curl supports .netrc files if told so (using the -n/--netrc option). This is
not restricted to only ftp, but curl can use it for all protocols where
authentication is used.
A very simple .netrc file could look something like:
machine curl.haxx.nu login iamdaniel password mysecret
CUSTOM OUTPUT
To better allow script programmers to get to know about the progress of
curl, the -w/--write-out option was introduced. Using this, you can specify
what information from the previous transfer you want to extract.
To display the amount of bytes downloaded together with some text and an
ending newline:
curl -w 'We downloaded %{size_download} bytes\n' www.download.com
MAILING LIST
We have an open mailing list to discuss curl, its development and things
relevant to this.
To subscribe, mail curl-request@contactor.se with "subscribe <your email
address>" in the body.
To post to the list, mail curl@contactor.se.
To unsubcribe, mail curl-request@contactor.se with "unsubscribe <your
subscribed email address>" in the body.

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How To Use Libcurl In Your Program:
(by Ralph Beckmann <rabe@uni-paderborn.de>)
NOTE: If you plan to use libcurl.a in Threads under Linux, do not use the old
gcc-2.7.x because the function 'gethostbyname' seems not to be thread-safe,
that is to say an unavoidable SEGMENTATION FAULT might occur.
1. a) In a C-Program:
#include "curl.h"
b) In a C++-Program:
extern "C" {
#include "curl.h"
}
2. char *url="http://www.domain.com";
curl_urlget (URGTAG_URL, url,
URGTAG_FLAGS, CONF_NOPROGRESS,
URGTAG_ERRORBUFFER, errorBuffer,
URGTAG_WRITEFUNCTION, (size_t (*)(void *, int, int, FILE
*))handle_data,
URGTAG_TIMEOUT, 30, /* or anything You want */
...
URGTAG_DONE);
3. size_t handle_data (const void *ptr, size_t size, size_t nitems,
FILE *stream)
{
(void)stream; /* stop complaining using g++ -Wall */
if ((int)nitems <= 0) {
return (size_t)0;
}
fprintf(stdout, (char *)ptr); /* or do anything else with it */
return nitems;
}
4. Compile Your Program with -I$(CURL_DIR)/include
5. Link Your Program together with $(CURL_DIR)/lib/libcurl.a
Small Example of How To Use libcurl
----------------------------------------------------------------------
/* Full example that uses libcurl.a to fetch web pages. */
/* curlthreads.c */
/* - Test-Program by Ralph Beckmann for using curl in POSIX-Threads */
/* Change *url1 and *url2 to textual long and slow non-FRAMESET websites! */
/*
1. Compile with gcc or g++ as $(CC):
$(CC) -c -Wall -pedantic curlthreads.c -I$(CURL_DIR)/include
2. Link with:
- Linux:
$(CC) -o curlthreads curlthreads.o $(CURL_DIR)/lib/libcurl.a -lpthread
-lm
- Solaris:
$(CC) -o curlthreads curlthreads.o $(CURL_DIR)/lib/libcurl.a -lpthread
-lm -lsocket -lnsl
*/
#include <pthread.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#include "curl.h"
}
#else
#include "curl.h"
#endif
size_t storedata (const void *ptr, size_t size, size_t nitems, FILE *stream) {
(void)ptr; (void)stream; /* just to stop g++ -Wall complaining */
fprintf(stdout, "Thread #%i reads %i Bytes.\n",
(int)pthread_self(), (int)(nitems*size));
return (nitems);
}
void *urlfetcher(void *url) {
curl_urlget (URGTAG_URL, url,
URGTAG_FLAGS, CONF_NOPROGRESS | CONF_FAILONERROR,
URGTAG_WRITEFUNCTION, (size_t (*)(void *, int, int, FILE
*))storedata,
URGTAG_DONE);
return NULL;
}
int main(void) {
char *url1="www.sun.com";
char *url2="www.microsoft.com";
pthread_t thread_id1, thread_id2;
pthread_create(&thread_id1, NULL, urlfetcher, (void *)url1);
pthread_create(&thread_id2, NULL, urlfetcher, (void *)url2);
pthread_join(thread_id1, NULL);
pthread_join(thread_id2, NULL);
fprintf(stdout, "Ready.\n");
return 0;
}

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This document has been introduced in order to let you find documents that
specify standards used by curl, software that extends curl and web pages with
"competing" utilities.
Standards
RFC 959 - Defines how FTP works
RFC 1738 - Uniform Resource Locators
RFC 1777 - defines the LDAP protocol
RFC 1808 - Relative Uniform Resource Locators
RFC 1867 - Form-based File Upload in HTML
RFC 1950 - ZLIB Compressed Data Format Specification
RFC 1951 - DEFLATE Compressed Data Format Specification
RFC 1952 - gzip compression format
RFC 1959 - LDAP URL syntax
RFC 2045-2049 - Everything you need to know about MIME! (needed for form
based upload)
RFC 2068 - HTTP 1.1 (obsoleted by RFC 2616)
RFC 2109 - HTTP State Management Mechanism (cookie stuff)
- Also, read Netscape's specification at
http://www.netscape.com/newsref/std/cookie_spec.html
RFC 2183 - "The Content-Disposition Header Field"
RFC 2229 - "A Dictionary Server Protocol"
RFC 2231 - "MIME Parameter Value and Encoded Word Extensions:
Character Sets, Languages, and Continuations"
RFC 2388 - "Returning Values from Forms: multipart/form-data"
Use this as an addition to the 1867
RFC 2396 - "Uniform Resource Identifiers: Generic Syntax and Semantics"
This one obsoletes 1738, but since 1738 is often mentioned I've left it
in this list.
RFC 2428 - "FTP Extensions for IPv6 and NATs"
This should be considered when introducing IPv6 awareness.
RFC 2616 - HTTP 1.1
RFC 2617 - HTTP Authentication
Compilers
MingW32 - http://www.xraylith.wisc.edu/~khan/software/gnu-win32/index.html
Software
OpenSSL - http://www.openssl.org
OpenLDAP - http://www.openldap.org
zlib - http://www.cdrom.com/pub/infozip/zlib/
Competitors
wget - ftp://prep.ai.mit.edu/pub/gnu/
snarf - http://www.xach.com/snarf/
lynx - http://lynx.browser.org/ (well at least when -dump is used)
swebget - http://www.uni-hildesheim.de/~smol0075/swebget/
fetch - ?

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TODO
Ok, this is what I wanna do with Curl. Please tell me what you think, and
please don't hesitate to contribute and send me patches that improve this
product! (Yes, you may add things not mentioned here, these are just a
few teasers...)
* rtsp:// support -- "Real Time Streaming Protocol"
RFC 2326
* "Content-Encoding: compress/gzip/zlib"
HTTP 1.1 clearly defines how to get and decode compressed documents. There
is the zlib that is pretty good at decompressing stuff. This work was
started in October 1999 but halted again since it proved more work than we
thought. It is still a good idea to implement though.
* HTTP Pipelining/persistant connections
- We should introduce HTTP "pipelining". Curl could be able to request for
several HTTP documents in one connect. It would be the beginning for
supporing more advanced functions in the future, like web site
mirroring. This will require that the urlget() function supports several
documents from a single HTTP server, which it doesn't today.
- When curl supports fetching several documents from the same server using
pipelining, I'd like to offer that function to the command line. Anyone has
a good idea how? The current way of specifying one URL with the output sent
to the stdout or a file gets in the way. Imagine a syntax that supports
"additional documents from the same server" in a way similar to:
curl <main URL> --more-doc <path> --more-doc <path>
where --more-doc specifies another document on the same server. Where are
the output files gonna be put and how should they be named? Should each
"--more-doc" parameter require a local file name to store the result in?
Like "--more-file" as in:
curl <URL> --more-doc <path> --more-file <file>
* RFC2617 compliance, "Digest Access Authentication"
A valid test page seem to exist at:
http://hopf.math.nwu.edu/testpage/digest/
And some friendly person's server source code is available at
http://hopf.math.nwu.edu/digestauth/index.html
Then there's the Apache mod_digest source code too of course. It seems as
if Netscape doesn't support this, and not many servers do. Although this is
a lot better authentication method than the more common "Basic". Basic
sends the password in cleartext over the network, this "Digest" method uses
a challange-response protocol which increases security quite a lot.
* Different FTP Upload Through Web Proxy
I don't know any web proxies that allow CONNECT through on port 21, but
that would be the best way to do ftp upload. All we would need to do would
be to 'CONNECT <host>:<port> HTTP/1.0\r\n\r\n' and then do business as
usual. I least I think so. It would be fun if someone tried this...
* Multiple Proxies?
Is there anyone that actually uses serial-proxies? I mean, send CONNECT to
the first proxy to connect to the second proxy to which you send CONNECT to
connect to the remote host (or even more iterations). Is there anyone
wanting curl to support it? (Not that it would be hard, just confusing...)
* Other proxies
Ftp-kind proxy, Socks5, whatever kind of proxies are there?
* IPv6 Awareness
Where ever it would fit. I am not that into v6 yet to fully grasp what we
would need to do, but letting the autoconf search for v6-versions of a few
functions and then use them instead is of course the first thing to do...
RFC 2428 "FTP Extensions for IPv6 and NATs" will be interesting. PORT
should be replaced with EPRT for IPv6, and EPSV instead of PASV.
* An automatic RPM package maker
Please, write me a script that makes it. It'd make my day.
* SSL for more protocols, like SSL-FTP...
(http://search.ietf.org/internet-drafts/draft-murray-auth-ftp-ssl-05.txt)
* HTTP POST resume using Range:
* Make curl capable of verifying the server's certificate when connecting
with HTTPS://.
* Make the timeout work as expected!

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.\" You can view this file with:
.\" nroff -man curl.1
.\" Written by Daniel Stenberg
.\"
.TH curl 1 "13 March 2000" "Curl 6.5" "Curl Manual"
.SH NAME
curl \- get a URL with FTP, TELNET, LDAP, GOPHER, DICT, FILE, HTTP or
HTTPS syntax.
.SH SYNOPSIS
.B curl [options]
.I url
.SH DESCRIPTION
.B curl
is a client to get documents/files from servers, using any of the
supported protocols. The command is designed to work without user
interaction or any kind of interactivity.
curl offers a busload of useful tricks like proxy support, user
authentication, ftp upload, HTTP post, SSL (https:) connections, cookies, file
transfer resume and more.
.SH URL
The URL syntax is protocol dependent. You'll find a detailed description in
RFC 2396.
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
It is possible to specify up to 9 sets or series for a URL, but no nesting is
supported at the moment:
http://www.any.org/archive[1996-1999]/volume[1-4]part{a,b,c,index}.html
.SH OPTIONS
.IP "-a/--append"
(FTP)
When used in a 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.
.IP "-A/--user-agent <agent string>"
(HTTP)
Specify the User-Agent string to send to the HTTP server. Some badly done CGIs
fail if its not 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
-H/--header flag of course.
.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 -L/--location option. The file format of the file
to read cookies from should be plain HTTP headers or the netscape cookie file
format.
.B NOTE
that the file specified with -b/--cookie is only used as input. No cookies
will be stored in the file. To store cookies, save the HTTP headers to a file
using -D/--dump-header!
.IP "-B/--ftp-ascii"
(FTP/LDAP)
Use ASCII transfer when getting an FTP file or LDAP info. For FTP, this can
also be enforced by using an URL that ends with ";type=A".
.IP "-c/--continue"
Continue/Resume a previous file transfer. This instructs curl to
continue appending data on the file where it was previously left,
possibly because of a broken connection to the server. There must be
a named physical file to append to for this to work.
Note: Upload resume is depening on a command named SIZE not always
present in all ftp servers! Upload resume is for FTP only.
HTTP resume is only possible with HTTP/1.1 or later servers.
.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 transfered
to the destination.
If used with uploads, the ftp server command SIZE will not be used by
curl. Upload resume is for FTP only.
HTTP resume is only possible with HTTP/1.1 or later servers.
.IP "-d/--data <data>"
(HTTP)
Sends the specified data in a POST request to the HTTP server. Note
that the data is sent exactly as specified with no extra processing.
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 -F.
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.
.IP "-D/--dump-header <file>"
(HTTP/FTP)
Write the HTTP headers to this file. Write the FTP file info to this
file if -I/--head is used.
This option is handy to use when you want to store the cookies that a HTTP
site sends to you. The cookies could then be read in a second curl invoke by
using the -b/--cookie option!
.IP "-e/--referer <URL>"
(HTTP)
Sends the "Referer Page" information to the HTTP server. Some badly
done CGIs fail if it's not set. This can also be set with the -H/--header
flag of course.
.IP "-E/--cert <certificate[:password]>"
(HTTPS)
Tells curl to use the specified certificate file when getting a file
with HTTPS. The certificate must be in PEM format.
If the optional password isn't specified, it will be queried for on
the terminal. Note that this certificate is the private key and the private
certificate concatenated!
.IP "-f/--fail"
(HTTP)
Fail silently (no output at all) on server errors. This is mostly done
like this to better enable scripts etc to better deal with failed
attempts. In normal cases when a HTTP server fails to deliver a
document, it returns a HTML document stating so (which often also
describes why and more). This flag will prevent curl from
outputting that and fail silently instead.
.IP "-F/--form <name=content>"
(HTTP)
This lets curl emulate a filled in form in which a user has pressed
the submit button. This causes curl to POST data using the
content-type multipart/form-data according to RFC1867. This enables
uploading of binary files etc. To force the 'content' part to be
read from a file, prefix the file name with an @ sign. Example, to
send your password file to the server, where 'password' is the
name of the form-field to which /etc/passwd will be the input:
.B curl
-F password=@/etc/passwd www.mypasswords.com
To read the file's content from stdin insted of a file, use - where the file
name should've been.
.IP "-h/--help"
Usage help.
.IP "-H/--header <header>"
(HTTP)
Extra header to use when getting a web page. You may specify any number of
extra headers. Note that if you should add a custom header that has the same
name as one of the internal ones curl would use, your externally set header
will be used instead of the internal one. This allows you to make even
trickier stuff than curl would normally do. You should not replace internally
set headers without knowing perfectly well what you're doing.
.IP "-i/--include"
(HTTP)
Include the HTTP-header in the output. The HTTP-header includes things
like server-name, date of the document, HTTP-version and more...
.IP "-I/--head"
(HTTP/FTP)
Fetch the HTTP-header only! HTTP-servers feature the command HEAD
which this uses to get nothing but the header of a document. When used
on a FTP file, curl displays the file size only.
.IP "-K/--config <config file>"
Specify which config file to read curl arguments from. The config
file is a text file in which command line arguments can be written
which then will be used as if they were written on the actual command
line. If the first column of a config line is a '#' character, the
rest of the line will be treated as a comment.
Specify the filename as '-' to make curl read the file from stdin.
.IP "-l/--list-only"
(FTP)
When listing an FTP directory, this switch forces a name-only view.
Especially useful if you want to machine-parse the contents of an FTP
directory since the normal directory view doesn't use a standard look
or format.
.IP "-L/--location"
(HTTP/HTTPS)
If the server reports that the requested page has a different location
(indicated with the header line Location:) this flag will let curl
attempt to reattempt the get on the new place. If used together with
-i or -I, headers from all requested pages will be shown.
.IP "-m/--max-time <seconds>"
Maximum time in seconds that you allow the whole operation to take.
This is useful for preventing your batch jobs from hanging for hours
due to slow networks or links going down.
This doesn't work properly in win32 systems.
.IP "-M/--manual"
Manual. Display the huge help text.
.IP "-n/--netrc"
Makes curl scan the
.I .netrc
file in the user's home directory for login name and password. This is
typically used for ftp on unix. If used with http, curl will enable user
authentication. See
.BR netrc(5)
for details on the file format. Curl will not complain if that file
hasn't the right permissions (it should not be world nor group
readable). The environment variable "HOME" is used to find the home
directory.
A quick and very simple example of how to setup a
.I .netrc
to allow curl to ftp to the machine host.domain.com with user name
'myself' and password 'secret' should look similar to:
.B "machine host.domain.com login myself password secret"
.IP "-N/--no-buffer"
Disables the buffering of the output stream. In normal work situations, curl
will use a standard buffered output stream that will have the effect that it
will output the data in chunks, not necessarily exactly when the data arrives.
Using this option will disable that buffering.
.IP "-o/--output <file>"
Write output to <file> instead of stdout. If you are using {} or [] to fetch
multiple documents, you can use '#' followed by a number in the <file>
specifier. That variable will be replaced with the current string for the URL
being fetched. Like in:
curl http://{one,two}.site.com -o "file_#1.txt"
or use several variables like:
curl http://{site,host}.host[1-5].com -o "#1_#2"
.IP "-O/--remote-name"
Write output to a local file named like the remote file we get. (Only
the file part of the remote file is used, the path is cut off.)
.IP "-P/--ftpport <address>"
(FTP)
Reverses the initiator/listener roles when connecting with ftp. This
switch makes Curl use the PORT command instead of PASV. In
practice, PORT tells the server to connect to the client's specified
address and port, while PASV asks the server for an ip address and
port to connect to. <address> should be one of:
.RS
.TP 12
.B interface
i.e "eth0" to specify which interface's IP address you want to use (Unix only)
.TP
.B "IP address"
i.e "192.168.10.1" to specify exact IP number
.TP
.B "host name"
i.e "my.host.domain" to specify machine
.TP
.B "-"
(any single-letter string) to make it pick the machine's default
.RE
.IP "-q"
If used as the first parameter on the command line, the
.I $HOME/.curlrc
file will not be read and used as a config file.
.IP "-Q/--quote <comand>"
(FTP) Send an arbitrary command to the remote FTP server, by using the QUOTE
command of the server. Not all servers support this command, and the set of
QUOTE commands are server specific! Quote commands are sent BEFORE the
transfer is taking place. To make commands take place after a successful
transfer, prefix them with a dash '-'. You may specify any amount of commands
to be run before and after the transfer. If the server returns failure for one
of the commands, the entire operation will be aborted.
.IP "-r/--range <range>"
(HTTP/FTP)
Retrieve a byte range (i.e a partial document) from a HTTP/1.1 or FTP
server. Ranges can be specified in a number of ways.
.RS
.TP 10
.B 0-499
specifies the first 500 bytes
.TP
.B 500-999
specifies the second 500 bytes
.TP
.B -500
specifies the last 500 bytes
.TP
.B 9500
specifies the bytes from offset 9500 and forward
.TP
.B 0-0,-1
specifies the first and last byte only(*)(H)
.TP
.B 500-700,600-799
specifies 300 bytes from offset 500(H)
.TP
.B 100-199,500-599
specifies two separate 100 bytes ranges(*)(H)
.RE
(*) = NOTE that this will cause the server to reply with a multipart
response!
You should also be aware that many HTTP/1.1 servers do not have this feature
enabled, so that when you attempt to get a range, you'll instead get the whole
document.
FTP range downloads only support the simple syntax 'start-stop' (optionally
with one of the numbers omitted). It depends on the non-RFC command SIZE.
.IP "-s/--silent"
Silent mode. Don't show progress meter or error messages. Makes
Curl mute.
.IP "-S/--show-error"
When used with -s it makes curl show error message if it fails.
.IP "-t/--upload"
Transfer the stdin data to the specified file. Curl will read
everything from stdin until EOF and store with the supplied name. If
this is used on a http(s) server, the PUT command will be used.
.IP "-T/--upload-file <file>"
Like -t, but this transfers the specified local file. If there is no
file part in the specified URL, Curl will append the local file
name. NOTE that you must use a trailing / on the last directory to
really prove to Curl that there is no file name or curl will
think that your last directory name is the remote file name to
use. That will most likely cause the upload operation to fail. If
this is used on a http(s) server, the PUT command will be used.
.IP "-u/--user <user:password>"
Specify user and password to use when fetching. See README.curl for detailed
examples of how to use this. If no password is specified, curl will
ask for it interactively.
.IP "-U/--proxy-user <user:password>"
Specify user and password to use for Proxy authentication. If no
password is specified, curl will ask for it interactively.
.IP "-v/--verbose"
Makes the fetching more verbose/talkative. Mostly usable for
debugging. Lines starting with '>' means data sent by curl, '<'
means data received by curl that is hidden in normal cases and lines
starting with '*' means additional info provided by curl.
.IP "-V/--version"
Displays the full version of curl, libcurl and other 3rd party libraries
linked with the executable.
.IP "-w/--write-out <format>"
Defines what to display after a completed and successful operation. The format
is a string that may contain plain text mixed with any number of variables. The
string can be specified as "string", to get read from a particular file you
specify it "@filename" and to tell curl to read the format from stdin you
write "@-".
The variables present in the output format will be substituted by the value or
text that curl thinks fit, as described below. All variables are specified
like %{variable_name} and to output a normal % you just write them like
%%. You can output a newline by using \\n, a carrige return with \\r and a tab
space with \\t.
.B NOTE:
The %-letter is a special letter in the win32-environment, where all
occurrences of % must be doubled when using this option.
Available variables are at this point:
.RS
.TP 15
.B url_effective
The URL that was fetched last. This is mostly meaningful if you've told curl
to follow location: headers.
.TP
.B http_code
The numerical code that was found in the last retrieved HTTP(S) page.
.TP
.B time_total
The total time, in seconds, that the full operation lasted. The time will be
displayed with millisecond resolution.
.TP
.B time_namelookup
The time, in seconds, it took from the start until the name resolving was
completed.
.TP
.B time_connect
The time, in seconds, it took from the start until the connect to the remote
host (or proxy) was completed.
.TP
.B time_pretransfer
The time, in seconds, it took from the start until the file transfer is just
about to begin. This includes all pre-transfer commands and negotiations that
are specific to the particular protocol(s) involved.
.TP
.B size_download
The total amount of bytes that were downloaded.
.TP
.B size_upload
The total amount of bytes that were uploaded.
.TP
.B speed_download
The average download speed that curl measured for the complete download.
.TP
.B speed_upload
The average upload speed that curl measured for the complete download.
.RE
.IP "-x/--proxy <proxyhost[:port]>"
Use specified proxy. If the port number is not specified, it is assumed at
port 1080.
.IP "-X/--request <command>"
(HTTP)
Specifies a custom request to use when communicating with the HTTP server.
The specified request will be used instead of the standard GET. Read the
HTTP 1.1 specification for details and explanations.
(FTP)
Specifies a custom FTP command to use instead of LIST when doing file lists
with ftp.
.IP "-y/--speed-time <time>"
If a download is slower than speed-limit bytes per second during a speed-time
period, the download gets aborted. If speed-time is used, the default
speed-limit will be 1 unless set with -y.
.IP "-Y/--speed-limit <speed>"
If a download is slower than this given speed, in bytes per second, for
speed-time seconds it gets aborted. speed-time is set with -Y and is 30 if
not set.
.IP "-z/--time-cond <date expression>"
(HTTP)
Request to get a file that has been modified later than the given time and
date, or one that has been modified before that time. The date expression can
be all sorts of date strings or if it doesn't match any internal ones, it
tries to get the time from a given file name instead! See the
.BR "GNU date(1)"
man page for date expression details.
Start the date expression with a dash (-) to make it request for a document
that is older than the given date/time, default is a document that is newer
than the specified date/time.
.IP "-3/--sslv3"
(HTTPS)
Forces curl to use SSL version 3 when negotiating with a remote SSL server.
.IP "-2/--sslv2"
(HTTPS)
Forces curl to use SSL version 2 when negotiating with a remote SSL server.
.IP "-#/--progress-bar"
Make curl display progress information as a progress bar instead of the
default statistics.
.IP "--crlf"
(FTP) Convert LF to CRLF in upload. Useful for MVS (OS/390).
.IP "--stderr <file>"
Redirect all writes to stderr to the specified file instead. If the file name
is a plain '-', it is instead written to stdout. This option has no point when
you're using a shell with decent redirecting capabilities.
.SH FILES
.I ~/.curlrc
.RS
Default config file.
.SH ENVIRONMENT
.IP "HTTP_PROXY [protocol://]<host>[:port]"
Sets proxy server to use for HTTP.
.IP "HTTPS_PROXY [protocol://]<host>[:port]"
Sets proxy server to use for HTTPS.
.IP "FTP_PROXY [protocol://]<host>[:port]"
Sets proxy server to use for FTP.
.IP "GOPHER_PROXY [protocol://]<host>[:port]"
Sets proxy server to use for GOPHER.
.IP "ALL_PROXY [protocol://]<host>[:port]"
Sets proxy server to use if no protocol-specific proxy is set.
.IP "NO_PROXY <comma-separated list of hosts>"
list of host names that shouldn't go through any proxy. If set to a
asterisk '*' only, it matches all hosts.
.IP "COLUMNS <integer>"
The width of the terminal. This variable only affects curl when the
--progress-bar option is used.
.SH EXIT CODES
There exists a bunch of different error codes and their corresponding error
messages that may appear during bad conditions. At the time of this writing,
the exit codes are:
.IP 1
Unsupported protocol. This build of curl has no support for this protocol.
.IP 2
Failed to initialize.
.IP 3
URL malformat. The syntax was not correct.
.IP 4
URL user malformatted. The user-part of the URL syntax was not correct.
.IP 5
Couldn't resolve proxy. The given proxy host could not be resolved.
.IP 6
Couldn't resolve host. The given remote host was not resolved.
.IP 7
Failed to connect to host.
.IP 8
FTP weird server reply. The server sent data curl couldn't parse.
.IP 9
FTP access denied. The server denied login.
.IP 10
FTP user/password incorrect. Either one or both were not accepted by the
server.
.IP 11
FTP weird PASS reply. Curl couldn't parse the reply sent to the PASS request.
.IP 12
FTP weird USER reply. Curl couldn't parse the reply sent to the USER request.
.IP 13
FTP weird PASV reply, Curl couldn't parse the reply sent to the PASV request.
.IP 14
FTP weird 227 formay. Curl couldn't parse the 227-line the server sent.
.IP 15
FTP can't get host. Couldn't resolve the host IP we got in the 227-line.
.IP 16
FTP can't reconnect. Couldn't connect to the host we got in the 227-line.
.IP 17
FTP couldn't set binary. Couldn't change transfer method to binary.
.IP 18
Partial file. Only a part of the file was transfered.
.IP 19
FTP couldn't RETR file. The RETR command failed.
.IP 20
FTP write error. The transfer was reported bad by the server.
.IP 21
FTP quote error. A quote command returned error from the server.
.IP 22
HTTP not found. The requested page was not found. This return code only
appears if --fail is used.
.IP 23
Write error. Curl couldn't write data to a local filesystem or similar.
.IP 24
Malformat user. User name badly specified.
.IP 25
FTP couldn't STOR file. The server denied the STOR operation.
.IP 26
Read error. Various reading problems.
.IP 27
Out of memory. A memory allocation request failed.
.IP 28
Operation timeout. The specified time-out period was reached according to the
conditions.
.IP 29
FTP couldn't set ASCII. The server returned an unknown reply.
.IP 30
FTP PORT failed. The PORT command failed.
.IP 31
FTP couldn't use REST. The REST command failed.
.IP 32
FTP couldn't use SIZE. The SIZE command failed. The command is an extension
to the original FTP spec RFC 959.
.IP 33
HTTP range error. The range "command" didn't work.
.IP 34
HTTP post error. Internal post-request generation error.
.IP 35
SSL connect error. The SSL handshaking failed.
.IP 36
FTP bad download resume. Couldn't continue an earlier aborted download.
.IP 37
FILE couldn't read file. Failed to open the file. Permissions?
.IP 38
LDAP cannot bind. LDAP bind operation failed.
.IP 39
LDAP search failed.
.IP 40
Library not found. The LDAP library was not found.
.IP 41
Function not found. A required LDAP function was not found.
.IP XX
There will appear more error codes here in future releases. The existing ones
are meant to never change.
.SH BUGS
If you do find any (or have other suggestions), mail Daniel Stenberg
<Daniel.Stenberg@haxx.nu>.
.SH AUTHORS / CONTRIBUTORS
- Daniel Stenberg <Daniel.Stenberg@haxx.nu>
- Rafael Sagula <sagula@inf.ufrgs.br>
- Sampo Kellomaki <sampo@iki.fi>
- Linas Vepstas <linas@linas.org>
- Bjorn Reese <breese@mail1.stofanet.dk>
- Johan Anderson <johan@homemail.com>
- Kjell Ericson <Kjell.Ericson@haxx,nu>
- Troy Engel <tengel@sonic.net>
- Ryan Nelson <ryan@inch.com>
- Bjorn Stenberg <Bjorn.Stenberg@haxx.nu>
- Angus Mackay <amackay@gus.ml.org>
- Eric Young <eay@cryptsoft.com>
- Simon Dick <simond@totally.irrelevant.org>
- Oren Tirosh <oren@monty.hishome.net>
- Steven G. Johnson <stevenj@alum.mit.edu>
- Gilbert Ramirez Jr. <gram@verdict.uthscsa.edu>
- Andrés García <ornalux@redestb.es>
- Douglas E. Wegscheid <wegscd@whirlpool.com>
- Mark Butler <butlerm@xmission.com>
- Eric Thelin <eric@generation-i.com>
- Marc Boucher <marc@mbsi.ca>
- Greg Onufer <Greg.Onufer@Eng.Sun.COM>
- Doug Kaufman <dkaufman@rahul.net>
- David Eriksson <david@2good.com>
- Ralph Beckmann <rabe@uni-paderborn.de>
- T. Yamada <tai@imasy.or.jp>
- Lars J. Aas <larsa@sim.no>
- Jörn Hartroth <Joern.Hartroth@telekom.de>
- Matthew Clarke <clamat@van.maves.ca>
- Linus Nielsen <Linus.Nielsen@haxx.nu>
- Felix von Leitner <felix@convergence.de>
- Dan Zitter <dzitter@zitter.net>
- Jongki Suwandi <Jongki.Suwandi@eng.sun.com>
- Chris Maltby <chris@aurema.com>
- Ron Zapp <rzapper@yahoo.com>
- Paul Marquis <pmarquis@iname.com>
- Ellis Pritchard <ellis@citria.com>
- Damien Adant <dams@usa.net>
- Chris <cbayliss@csc.come>
- Marco G. Salvagno <mgs@whiz.cjb.net>
.SH WWW
http://curl.haxx.nu
.SH FTP
ftp://ftp.sunet.se/pub/www/utilities/curl/
.SH "SEE ALSO"
.BR ftp (1),
.BR wget (1),
.BR snarf (1)