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curl/docs/libcurl/curl_formadd.3
Daniel Stenberg c2bc47ddb8 curl_formadd.3: *_FILECONTENT and *_FILE need the file to be kept 
Reported-by: Frank Gevaerts
2016-11-08 15:28:04 +01:00

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.\" **************************************************************************
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.\" * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
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.\" * are also available at https://curl.haxx.se/docs/copyright.html.
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.\" * furnished to do so, under the terms of the COPYING file.
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.TH curl_formadd 3 "24 June 2002" "libcurl 7.9.8" "libcurl Manual"
.SH NAME
curl_formadd - add a section to a multipart/formdata HTTP POST
.SH SYNOPSIS
.B #include <curl/curl.h>
.sp
.BI "CURLFORMcode curl_formadd(struct curl_httppost ** " firstitem,
.BI "struct curl_httppost ** " lastitem, " ...);"
.ad
.SH 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 \fIfirstitem\fP pointer as parameter to \fICURLOPT_HTTPPOST(3)\fP.
\fIlastitem\fP is set after each \fIcurl_formadd(3)\fP 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 \fIlastitem\fP pointer follow the real arguments.
The pointers \fIfirstitem\fP and \fIlastitem\fP 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 \fIcurl_formfree(3)\fP on the
\fIfirstitem\fP 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 \fICURLOPT_HTTPHEADER(3)\fP 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
\fICURLFORM_FILE\fP through \fICURLFORM_BUFFERLENGTH\fP are for file upload
parts.
.SH OPTIONS
.IP CURLFORM_COPYNAME
followed by a string which provides the \fIname\fP 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
\fBCURLFORM_NAMELENGTH\fP. The copied data will be freed by
\fIcurl_formfree(3)\fP.
.IP CURLFORM_PTRNAME
followed by a string which provides the \fIname\fP 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 \fBCURLFORM_NAMELENGTH\fP.
.IP 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 \fBCURLFORM_CONTENTSLENGTH\fP. The copied
data will be freed by \fIcurl_formfree(3)\fP.
.IP 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 \fBCURLFORM_CONTENTSLENGTH\fP.
.IP CURLFORM_CONTENTLEN
followed by a curl_off_t value giving the length of the contents. Note that
for \fICURLFORM_STREAM\fP 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)
.IP CURLFORM_CONTENTSLENGTH
(This option is deprecated. Use \fICURLFORM_CONTENTLEN\fP instead!)
followed by a long giving the length of the contents. Note that for
\fICURLFORM_STREAM\fP 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.
.IP CURLFORM_FILECONTENT
followed by a filename, causes that file to be read and its contents used
as data in this part. This part does \fInot\fP 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.
.IP CURLFORM_FILE
followed by a filename, makes this part a file upload part. It sets the
\fIfilename\fP 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
\fBCURLFORM_FILE\fP the user may send one or more files in one part by
providing multiple \fBCURLFORM_FILE\fP arguments each followed by the filename
(and each \fICURLFORM_FILE\fP is allowed to have a
\fICURLFORM_CONTENTTYPE\fP).
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.
.IP CURLFORM_CONTENTTYPE
is used in combination with \fICURLFORM_FILE\fP. Followed by a pointer to a
string which provides the content-type for this part, possibly instead of an
internally chosen one.
.IP CURLFORM_FILENAME
is used in combination with \fICURLFORM_FILE\fP. Followed by a pointer to a
string, it tells libcurl to use the given string as the \fIfilename\fP in the
file upload part instead of the actual file name.
.IP CURLFORM_BUFFER
is used for custom file upload parts without use of \fICURLFORM_FILE\fP. It
tells libcurl that the file contents are already present in a buffer. The
parameter is a string which provides the \fIfilename\fP field in the content
header.
.IP CURLFORM_BUFFERPTR
is used in combination with \fICURLFORM_BUFFER\fP. The parameter is a pointer
to the buffer to be uploaded. This buffer must not be freed until after
\fIcurl_easy_cleanup(3)\fP is called. You must also use
\fICURLFORM_BUFFERLENGTH\fP to set the number of bytes in the buffer.
.IP CURLFORM_BUFFERLENGTH
is used in combination with \fICURLFORM_BUFFER\fP. The parameter is a
long which gives the length of the buffer.
.IP CURLFORM_STREAM
Tells libcurl to use the \fICURLOPT_READFUNCTION(3)\fP callback to get
data. The parameter you pass to \fICURLFORM_STREAM\fP 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 \fICURLFORM_FILENAME\fP parameter as well. Note that
when using \fICURLFORM_STREAM\fP, \fICURLFORM_CONTENTSLENGTH\fP must also be
set with the total expected length of the part. (Option added in libcurl
7.18.2)
.IP CURLFORM_ARRAY
Another possibility to send options to curl_formadd() is the
\fBCURLFORM_ARRAY\fP 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 \fBCURLFORM_END\fP.
.IP CURLFORM_CONTENTHEADER
specifies extra headers for the form POST section. This takes a curl_slist
prepared in the usual way using \fBcurl_slist_append\fP 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 \fIcurl_easy_setopt(3)\fP (using
the \fICURLOPT_HTTPPOST(3)\fP option), you must not free the list until after
you've called \fIcurl_easy_cleanup(3)\fP for the curl handle.
See example below.
.SH RETURN VALUE
0 means everything was ok, non-zero means an error occurred corresponding
to a CURL_FORMADD_* constant defined in
.I <curl/curl.h>
.SH EXAMPLE
.nf
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);
.SH "SEE ALSO"
.BR curl_easy_setopt "(3), "
.BR curl_formfree "(3)"
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