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curl/docs/cmdline-opts/form.md
Daniel Stenberg e7219c2bdc
cmdline-opts: language cleanups
Use imperative mood consistently for the first sentence describing an
option.

"Set this" instead "tell curl to set" or "this sets..."

Plus some extra cleanups and rephrasing.

Closes 
2024-03-12 15:42:33 +01:00

5.0 KiB

c SPDX-License-Identifier Long Short Arg Help Protocols Mutexed Category Added Multi See-also Example
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. curl form F <name=content> Specify multipart MIME data HTTP SMTP IMAP data head upload-file http upload 5.0 append
data
form-string
form-escape
--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\"" example.com

or

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

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.