curl_formadd(3) libcurl Manual curl_formadd(3)
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 rfc1867-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. lastitem
is set after each 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 func-tion. function.
tion. All list-data will be allocated by the function itself. You must call curl_formfree(3) 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 as usual.
First, there are some basics you need to understand about multipart/formdata posts. Each part con-sists consists
sists 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 proper-ties properties
ties 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 CURL-FORM_BUFFERLENGTH CURLFORM_BUFFERLENGTH
FORM_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 null
terminated, or if you'd like it to contain zero bytes, you must set its length with CURL-FORM_NAMELENGTH. CURLFORM_NAMELENGTH.
FORM_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 null 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 func-tion function
tion 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 null terminated, or if you'd like it to con-tain contain
tain zero bytes, you must set its length with CURLFORM_CONTENTSLENGTH.
CURLFORM_CONTENTSLENGTH
followed by a long giving the length of the contents.
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 CURL-FORM_FILE CURLFORM_FILE
FORM_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_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 automati-cally automatically
cally 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
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 as <curl/curl.h> defines.
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)
libcurl 7.9.8 24 June 2002 curl_formadd(3)
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