`--form`

For the HTTP protocol family, emulate a filled-in form in which a user has pressed the submit button. This makes curl POST data using the Content-Type multipart/form-data according to RFC 2388.

For SMTP and IMAP protocols, this composes a multipart mail message to transmit.

This enables uploading of binary files etc. To force the 'content' part to be a file, prefix the filename with an @ sign. To just get the content part from a file, prefix the filename with the symbol <. The difference between @ and < is then that @ makes a file get attached in the post as a file upload, while the < makes a text field and just get the contents for that text field from a file.

Read content from stdin instead of a file by using a single "-" as filename. This goes for both @ and < constructs. When stdin is used, the contents is buffered in memory first by curl to determine its size and allow a possible resend. Defining a part's data from a named non-regular file (such as a named pipe or similar) is not subject to buffering and is instead read at transmission time; since the full size is unknown before the transfer starts, such data is sent as chunks by HTTP and rejected by IMAP.

Example: send an image to an HTTP server, where 'profile' is the name of the form-field to which the file portrait.jpg is the input:

curl -F profile=@portrait.jpg https://example.com/upload.cgi

Example: send your name and shoe size in two text fields to the server:

curl -F name=John -F shoesize=11 https://example.com/

Example: send your essay in a text field to the server. Send it as a plain text field, but get the contents for it from a local file:

curl -F "story=<hugefile.txt" https://example.com/

You can also instruct curl what Content-Type to use by using type=, in a manner similar to:

curl -F "web=@index.html;type=text/html" example.com

curl -F "name=daniel;type=text/foo" example.com

You can also explicitly change the name field of a file upload part by setting filename=, like this:

curl -F "file=@localfile;filename=nameinpost" example.com

If filename/path contains ',' or ';', it must be quoted by double-quotes like:

curl -F "file=@\"local,file\";filename=\"name;in;post\"" example.com

curl -F 'file=@"local,file";filename="name;in;post"' example.com

Note that if a filename/path is quoted by double-quotes, any double-quote or backslash within the filename must be escaped by backslash.

Quoting must also be applied to non-file data if it contains semicolons, leading/trailing spaces or leading double quotes:

curl -F 'colors="red; green; blue";type=text/x-myapp' example.com

You can add custom headers to the field by setting headers=, like

curl -F "submit=OK;headers=\"X-submit-type: OK\"" example.com

curl -F "submit=OK;headers=@headerfile" example.com

The headers= keyword may appear more that once and above notes about quoting apply. When headers are read from a file, Empty lines and lines starting with '#' are comments and ignored; each header can be folded by splitting between two words and starting the continuation line with a space; embedded carriage-returns and trailing spaces are stripped. Here is an example of a header file contents:

# This file contain two headers.
X-header-1: this is a header

# The following header is folded.
X-header-2: this is
 another header

To support sending multipart mail messages, the syntax is extended as follows:

name can be omitted: the equal sign is the first character of the argument,
if data starts with '(', this signals to start a new multipart: it can be followed by a content type specification.
a multipart can be terminated with a '=)' argument.

Example: the following command sends an SMTP mime email consisting in an inline part in two alternative formats: plain text and HTML. It attaches a text file:

curl -F '=(;type=multipart/alternative' \
     -F '=plain text message' \
     -F '= <body>HTML message</body>;type=text/html' \
     -F '=)' -F '=@textfile.txt' ...  smtp://example.com

Data can be encoded for transfer using encoder=. Available encodings are binary and 8bit that do nothing else than adding the corresponding Content-Transfer-Encoding header, 7bit that only rejects 8-bit characters with a transfer error, quoted-printable and base64 that encodes data according to the corresponding schemes, limiting lines length to 76 characters.

Example: send multipart mail with a quoted-printable text message and a base64 attached file:

curl -F '=text message;encoder=quoted-printable' \
     -F '=@localfile;encoder=base64' ... smtp://example.com

See further examples and details in the MANUAL.

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--form

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`--form`