NAME¶
curl_formadd - add a section to a multipart/formdata HTTP POST
SYNOPSIS¶
#include <curl/curl.h>
CURLFORMcode curl_formadd(struct curl_httppost ** firstitem,
struct curl_httppost ** lastitem, ...);
DESCRIPTION¶
curl_formadd() is used to append sections when building a multipart/formdata
HTTP POST (sometimes referred to as RFC2388-style posts). Append one section
at a time until you've added all the sections you want included and then you
pass the
firstitem pointer as parameter to
CURLOPT_HTTPPOST(3).
lastitem is set after each
curl_formadd(3) call and on repeated
invokes it should be left as set to allow repeated invokes to find the end of
the list faster.
After the
lastitem pointer follow the real arguments.
The pointers
firstitem and
lastitem should both be pointing to
NULL in the first call to this function. All list-data will be allocated by
the function itself. You must call
curl_formfree(3) on the
firstitem after the form post has been done to free the resources.
Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue"
header. You can disable this header with
CURLOPT_HTTPHEADER(3) as
usual.
First, there are some basics you need to understand about multipart/formdata
posts. Each part consists of at least a NAME and a CONTENTS part. If the part
is made for file upload, there are also a stored CONTENT-TYPE and a FILENAME.
Below, we'll discuss what options you use to set these properties in the parts
you want to add to your post.
The options listed first are for making normal parts. The options from
CURLFORM_FILE through
CURLFORM_BUFFERLENGTH are for file upload
parts.
OPTIONS¶
- CURLFORM_COPYNAME
- followed by a string which provides the name of this part. libcurl
copies the string so your application doesn't need to keep it around after
this function call. If the name isn't NUL-terminated, or if you'd like it
to contain zero bytes, you must set its length with
CURLFORM_NAMELENGTH. The copied data will be freed by
curl_formfree(3).
- CURLFORM_PTRNAME
- followed by a string which provides the name of this part. libcurl
will use the pointer and refer to the data in your application, so you
must make sure it remains until curl no longer needs it. If the name isn't
NUL-terminated, or if you'd like it to contain zero bytes, you must set
its length with CURLFORM_NAMELENGTH.
- CURLFORM_COPYCONTENTS
- followed by a pointer to the contents of this part, the actual data to
send away. libcurl copies the provided data, so your application doesn't
need to keep it around after this function call. If the data isn't null
terminated, or if you'd like it to contain zero bytes, you must set the
length of the name with CURLFORM_CONTENTSLENGTH. The copied data
will be freed by curl_formfree(3).
- CURLFORM_PTRCONTENTS
- followed by a pointer to the contents of this part, the actual data to
send away. libcurl will use the pointer and refer to the data in your
application, so you must make sure it remains until curl no longer needs
it. If the data isn't NUL-terminated, or if you'd like it to contain zero
bytes, you must set its length with CURLFORM_CONTENTSLENGTH.
- CURLFORM_CONTENTSLENGTH
- followed by a long giving the length of the contents. Note that for
CURLFORM_STREAM contents, this option is mandatory.
If you pass a 0 (zero) for this option, libcurl will instead do a strlen()
on the contents to figure out the size. If you really want to send a zero
byte content then you must make sure strlen() on the data pointer returns
zero.
- CURLFORM_FILECONTENT
- followed by a filename, causes that file to be read and its contents used
as data in this part. This part does not automatically become a
file upload part simply because its data was read from a file.
- CURLFORM_FILE
- followed by a filename, makes this part a file upload part. It sets the
filename field to the basename of the provided filename, it reads
the contents of the file and passes them as data and sets the content-type
if the given file match one of the internally known file extensions. For
CURLFORM_FILE the user may send one or more files in one part by
providing multiple CURLFORM_FILE arguments each followed by the
filename (and each CURLFORM_FILE is allowed to have a
CURLFORM_CONTENTTYPE).
- CURLFORM_CONTENTTYPE
- is used in combination with CURLFORM_FILE. Followed by a pointer to
a string which provides the content-type for this part, possibly instead
of an internally chosen one.
- CURLFORM_FILENAME
- is used in combination with CURLFORM_FILE. Followed by a pointer to
a string, it tells libcurl to use the given string as the filename
in the file upload part instead of the actual file name.
- CURLFORM_BUFFER
- is used for custom file upload parts without use of CURLFORM_FILE.
It tells libcurl that the file contents are already present in a buffer.
The parameter is a string which provides the filename field in the
content header.
- CURLFORM_BUFFERPTR
- is used in combination with CURLFORM_BUFFER. The parameter is a
pointer to the buffer to be uploaded. This buffer must not be freed until
after curl_easy_cleanup(3) is called. You must also use
CURLFORM_BUFFERLENGTH to set the number of bytes in the
buffer.
- CURLFORM_BUFFERLENGTH
- is used in combination with CURLFORM_BUFFER. The parameter is a
long which gives the length of the buffer.
- CURLFORM_STREAM
- Tells libcurl to use the CURLOPT_READFUNCTION(3) callback to get
data. The parameter you pass to CURLFORM_STREAM is the pointer
passed on to the read callback's fourth argument. If you want the part to
look like a file upload one, set the CURLFORM_FILENAME parameter as
well. Note that when using CURLFORM_STREAM,
CURLFORM_CONTENTSLENGTH must also be set with the total expected
length of the part. (Option added in libcurl 7.18.2)
- CURLFORM_ARRAY
- Another possibility to send options to curl_formadd() is the
CURLFORM_ARRAY option, that passes a struct curl_forms array
pointer as its value. Each curl_forms structure element has a
CURLformoption and a char pointer. The final element in the array must be
a CURLFORM_END. All available options can be used in an array, except the
CURLFORM_ARRAY option itself! The last argument in such an array must
always be CURLFORM_END.
- CURLFORM_CONTENTHEADER
- specifies extra headers for the form POST section. This takes a curl_slist
prepared in the usual way using curl_slist_append and appends the
list of headers to those libcurl automatically generates. The list must
exist while the POST occurs, if you free it before the post completes you
may experience problems.
When you've passed the HttpPost pointer to curl_easy_setopt(3) (using
the CURLOPT_HTTPPOST(3) option), you must not free the list until
after you've called curl_easy_cleanup(3) for the curl handle.
See example below.
RETURN VALUE¶
0 means everything was ok, non-zero means an error occurred corresponding to a
CURL_FORMADD_* constant defined in
<curl/curl.h>
EXAMPLE¶
struct curl_httppost* post = NULL;
struct curl_httppost* last = NULL;
char namebuffer[] = "name buffer";
long namelength = strlen(namebuffer);
char buffer[] = "test buffer";
char htmlbuffer[] = "<HTML>test buffer</HTML>";
long htmlbufferlength = strlen(htmlbuffer);
struct curl_forms forms[3];
char file1[] = "my-face.jpg";
char file2[] = "your-face.jpg";
/* add null character into htmlbuffer, to demonstrate that
transfers of buffers containing null characters actually work
*/
htmlbuffer[8] = '\0';
/* Add simple name/content section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "name",
CURLFORM_COPYCONTENTS, "content", CURLFORM_END);
/* Add simple name/content/contenttype section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "htmlcode",
CURLFORM_COPYCONTENTS, "<HTML></HTML>",
CURLFORM_CONTENTTYPE, "text/html", CURLFORM_END);
/* Add name/ptrcontent section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "name_for_ptrcontent",
CURLFORM_PTRCONTENTS, buffer, CURLFORM_END);
/* Add ptrname/ptrcontent section */
curl_formadd(&post, &last, CURLFORM_PTRNAME, namebuffer,
CURLFORM_PTRCONTENTS, buffer, CURLFORM_NAMELENGTH,
namelength, CURLFORM_END);
/* Add name/ptrcontent/contenttype section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "html_code_with_hole",
CURLFORM_PTRCONTENTS, htmlbuffer,
CURLFORM_CONTENTSLENGTH, htmlbufferlength,
CURLFORM_CONTENTTYPE, "text/html", CURLFORM_END);
/* Add simple file section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "picture",
CURLFORM_FILE, "my-face.jpg", CURLFORM_END);
/* Add file/contenttype section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "picture",
CURLFORM_FILE, "my-face.jpg",
CURLFORM_CONTENTTYPE, "image/jpeg", CURLFORM_END);
/* Add two file section */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "pictures",
CURLFORM_FILE, "my-face.jpg",
CURLFORM_FILE, "your-face.jpg", CURLFORM_END);
/* Add two file section using CURLFORM_ARRAY */
forms[0].option = CURLFORM_FILE;
forms[0].value = file1;
forms[1].option = CURLFORM_FILE;
forms[1].value = file2;
forms[2].option = CURLFORM_END;
/* Add a buffer to upload */
curl_formadd(&post, &last,
CURLFORM_COPYNAME, "name",
CURLFORM_BUFFER, "data",
CURLFORM_BUFFERPTR, record,
CURLFORM_BUFFERLENGTH, record_length,
CURLFORM_END);
/* no option needed for the end marker */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "pictures",
CURLFORM_ARRAY, forms, CURLFORM_END);
/* Add the content of a file as a normal post text value */
curl_formadd(&post, &last, CURLFORM_COPYNAME, "filecontent",
CURLFORM_FILECONTENT, ".bashrc", CURLFORM_END);
/* Set the form info */
curl_easy_setopt(curl, CURLOPT_HTTPPOST, post);
SEE ALSO¶
curl_easy_setopt(3),
curl_formfree(3)