Tribblix: manual page: curl

curl_formadd(3) Introduction to Library Functions curl_formadd(3)

NAME

curl_formadd - add a section to a multipart form POST

SYNOPSIS

#include <curl/curl.h>

CURLFORMcode curl_formadd(struct curl_httppost **firstitem,
struct curl_httppost **lastitem, ...);

DESCRIPTION

This function is deprecated. Use curl_mime_init(3) instead.

curl_formadd() is used to append sections when building a multipart
form post. 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 is 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
form 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 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
null-terminated, you must set its length with
CURLFORM_NAMELENGTH. The name is not allowed to contain
zero-valued bytes. The copied data is freed by
curl_formfree(3).

CURLFORM_PTRNAME
followed by a string which provides the name of this part.
libcurl uses 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 null-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 is
freed by curl_formfree(3).

CURLFORM_PTRCONTENTS
followed by a pointer to the contents of this part, the actual
data to send away. libcurl uses 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
null-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 calls 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.

If you pass a 0 (zero) for this option, libcurl calls 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.

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
filename.

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 struct curl_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.

PROTOCOLS

This functionality affects http only

EXAMPLE

#include <string.h> /* for strlen */

static const char record[]="data in a buffer";

int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
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, sizeof(record),
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);

curl_easy_perform(curl);

curl_easy_cleanup(curl);

curl_formfree(post);
}
}

DEPRECATED

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 filenames are now escaped
before transmission.

AVAILABILITY

Added in curl 7.1

RETURN VALUE

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