xref: /aosp_15_r20/external/curl/docs/cmdline-opts/form.md (revision 6236dae45794135f37c4eb022389c904c8b0090d)

---
c: Copyright (C) Daniel Stenberg, <[email protected]>, et al.
SPDX-License-Identifier: curl
Long: form
Short: F
Arg: <name=content>
Help: Specify multipart MIME data
Protocols: HTTP SMTP IMAP
Mutexed: data head upload-file
Category: http upload post imap smtp
Added: 5.0
Multi: append
See-also:
  - data
  - form-string
  - form-escape
Example:
  - --form "name=curl" --form "file=@loadthis" $URL
---

# `--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

or

    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\"" \
        https://example.com

or

    curl -F 'file=@"local,file";filename="name;in;post"' \
        https://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' \
       https://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

or

    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.