Ubuntu Manpage: curl_formadd - add a section to a multipart/formdata HTTP POST

Provided by: libcurl4-doc_7.81.0-1ubuntu1.19_all

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

       This function is deprecated. Do not use. See curl_mime_init(3) instead.

       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
       have  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 will 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 does not need to keep it around after this function
call. If the name is not NUL-terminated, you must set its length with
CURLFORM_NAMELENGTH. The name is not allowed to contain zero-valued bytes. 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 is not NUL-terminated, you must set its
length with CURLFORM_NAMELENGTH. The name is not allowed to contain zero-valued
bytes.

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 does not need to keep it
around after this function call. If the data is not null terminated, or if you
would 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 is not NUL-
terminated, or if you would like it to contain zero bytes, you must set its length
with CURLFORM_CONTENTSLENGTH.

CURLFORM_CONTENTLEN
followed by a curl_off_t value 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.

(Option added in 7.46.0)

CURLFORM_CONTENTSLENGTH
(This option is deprecated. Use CURLFORM_CONTENTLEN instead!)

followed by a long giving the length of the contents. Note that for CURLFORM_STREAM
contents, this option is mandatory.

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.

The specified file needs to kept around until the associated transfer is done.

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).

The given upload file has to exist in its full in the file system already when the
upload starts, as libcurl needs to read the correct file size beforehand.

The specified file needs to kept around until the associated transfer is done.

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
unless the formpost is sent chunked encoded. (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 have passed the HttpPost pointer to curl_easy_setopt(3) (using the
CURLOPT_HTTPPOST(3) option), you must not free the list until after you have called
curl_easy_cleanup(3) for the curl handle.

See example below.

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);

AVAILABILITY

       Deprecated in 7.56.0. Before this release, field names were allowed to contain zero-valued
       bytes.  The pseudo-filename "-" to read stdin is discouraged although still supported, but
       data is not read before being actually sent: the effective  data  size  can  then  not  be
       automatically determined, resulting in a chunked encoding transfer. Backslashes and double
       quotes in field and file names are now escaped before transmission.

RETURN VALUE

       0  means  everything  was  ok,  non-zero  means  an  error  occurred  corresponding  to  a
       CURL_FORMADD_* constant defined in <curl/curl.h>