curl_formadd

Section: libcurl Manual (3)
Updated: 1 Match 2002
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NAME

curl_formadd - add a section to a multipart/formdata HTTP POST

SYNOPSIS

#include <curl/curl.h>

int curl_formadd(struct HttpPost ** firstitem, struct HttpPost ** lastitem, ...);

DESCRIPTION

curl_formadd() is used to append sections when building a multipart/formdata HTTP POST (sometimes refered 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. (If the following description confuses you, jump directly to the examples):

CURLFORM_COPYNAME or CURLFORM_PTRNAME followed by a string is used for the name of the section. Optionally one may use CURLFORM_NAMELENGTH to specify the length of the name (allowing null characters within the name). All options that use the word COPY in their names copy the given contents, while the ones with PTR in their names simply points to the (static) data you must make sure remain until curl no longer needs it.

The four options for providing values are: CURLFORM_COPYCONTENTS, CURLFORM_PTRCONTENTS, CURLFORM_FILE, or CURLFORM_FILECONTENT followed by a char or void pointer (allowed for PTRCONTENTS).

CURLFORM_FILECONTENT does a normal post like CURLFORM_COPYCONTENTS but the actual value is read from the filename given as a string.

Other arguments may be CURLFORM_CONTENTTYPE if the user wishes to specify one (for FILE if no type is given the library tries to provide the correct one; for CONTENTS no Content-Type is sent in this case).

For CURLFORM_PTRCONTENTS or CURLFORM_COPYNAME the user may also add CURLFORM_CONTENTSLENGTH followed by the length as a long (if not given the library will use strlen to determine the length).

For CURLFORM_FILE the user may send multiple files in one section by providing multiple CURLFORM_FILE arguments each followed by the filename (and each FILE is allowed to have a CONTENTTYPE).

Another possibility to send single or multiple files in one section is to use CURLFORM_ARRAY that gets a struct curl_forms array pointer as its value. Each structure element has a CURLformoption and a char pointer. For the options only CURLFORM_FILE, CURLFORM_CONTENTTYPE, and CURLFORM_END (that is used to determine the end of the array and thus must be the option of the last and no other element of the curl_forms array) are allowed. The effect of this parameter is the same as giving multiple CURLFORM_FILE options possibly with CURLFORM_CONTENTTYPE after or before each CURLFORM_FILE option.

Should you need to specify extra headers for the form POST section, use CURLFORM_CONTENTHEADER. This takes a curl_slist prepared in the usual way using curl_slist_append and appends the list of headers to those Curl automatically generates for CURLFORM_CONTENTTYPE and the content disposition. The list must exist while the POST occurs, if you free it before the post completes you may experience problems.

The last argument in such an array must always be CURLFORM_END.

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 after the form post has been done to free the resources again.

This function will copy all input data except the data pointed to by the arguments after CURLFORM_PTRNAME and CURLFORM_PTRCONTENTS and keep its own version of it allocated until you call curl_formfree. When you've passed the pointer to curl_easy_setopt, you must not free the list until after you've called curl_easy_cleanup for the curl handle. If you provide a pointer as an arguments after CURLFORM_PTRNAME or CURLFORM_PTRCONTENTS you must ensure that the pointer stays valid until you call curl_form_free and curl_easy_cleanup.

See example below.

RETURN VALUE

Returns non-zero if an error occurs.

EXAMPLE


 struct HttpPost* post = NULL;
 struct 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;

 /* 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);

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Time: 14:34:05 GMT, April 25, 2024