How can I rewrite this CURL multipart/form-data request without using -F?

Question

How can I rewrite the following CURL command, so that it doesn't use the -F option, but still generates the exact same HTTP request? i.e. so that it passes the multipart/form-data in the body directly.

curl -X POST -F example=test http://localhost:3000/test

Answer 1

Solved:

curl \
  -X POST \
  -H "Content-Type: multipart/form-data; boundary=----------------------------4ebf00fbcf09" \
  --data-binary @test.txt \
  http://localhost:3000/test

Where test.txt contains the following text, and most importantly has CRLF (\r\n) line endings:

------------------------------4ebf00fbcf09
Content-Disposition: form-data; name="example"

test
------------------------------4ebf00fbcf09--

Notes: it is important to use --data-binary instead of plain old -d as the former preserves the line endings (which are very important). Also, note that the boundary in the body starts with an extra --.

I'm going to repeat it because it's so important, but that request-body file must have CRLF line endings. A multi-platform text editor with good line-ending support is jEdit (how to set the line endings in jEdit).

If you're interested in how I worked this out (debugging with a Ruby on Rails app) and not just the final solution, I wrote up my debugging steps on my blog.

Answer 2

You can use the --form argument with an explicitly

curl -H "Content-Type: multipart/related" \
  --form "[email protected];type=image/jpeg" http://localhost:3000/test

Answer 3

Here's an alternative answer with the original CURL statement re-written using -d as a one-liner, without temporary files. Personally I think the temporary files approach is easier to understand, but I'm putting this here for reference as well:

curl -X POST -H "Content-Type: multipart/form-data; boundary=----------------------------4ebf00fbcf09" -d $'------------------------------4ebf00fbcf09\r\nContent-Disposition: form-data; name="example"\r\n\r\ntest\r\n------------------------------4ebf00fbcf09--\r\n' http://localhost:3000/test

Notes: the $'blar' syntax is so that bash will parse the \r\n as a CRLF token. Thanks to this answer for that tip.

Answer 4

This is what I'm using, I think it's clean and doesn't need temporary files nor gobbles up RAM in case you want to upload whole files (so no reading files into memory).

# Set these two.
file='path/to/yourfile.ext'
url='http://endpoint.example.com/foo/bar'

delim="-----MultipartDelimeter$$$RANDOM$RANDOM$RANDOM"
nl=$'\r\n'
mime="$(file -b --mime-type "$file")"

# This is the "body" of the request.
data() {
    # Also make sure to set the fields you need.
    printf %s "--$delim${nl}Content-Disposition: form-data; name=\"userfile\"${nl}Content-Type: $mime$nl$nl"
    cat "$file"
    printf %s "$nl--$delim--$nl"
}

# You can later grep this, or something.
response="$(data | curl -# "$url" -H "content-type: multipart/form-data; boundary=$delim" --data-binary @-)"

Answer 5

This is to upload one image file using "Content-Type: multipart/related",

curl --trace trace.txt -X POST -H 'Content-Type: multipart/related; boundary=boundary_1234' --data-binary $'--boundary_1234\r\nContent-Type: application/json; charset=UTF-8\r\n\r\n{\r\n\t"title": "TestFile"\r\n}\r\n\r\n--boundary_1234\r\nContent-Type: image/jpeg\r\n\r\n' --data-binary '@Image0177.jpg' --data-binary $'\r\n--boundary_1234--\r\n' 'http://localhost:3000/google/upload/drive/v2/files?uploadType=multipart'

Answer 6

Here it is how I would do it:

curl https://httpbin.org/post \
    -H 'content-type: multipart/form-data; boundary=----FormBoundary123456789' \
    --data-binary $'------FormBoundary123456789\r
Content-Disposition: form-data; name="example"\r
\r
test\r
------FormBoundary123456789--\r
'

Or a bit more sophisticated (should be portable to most modern shells):

DELIM=----FormBoundary$RANDOM$RANDOM

curl https://httpbin.org/post \
    -H "content-type: multipart/form-data; boundary=$DELIM" \
    --data-binary --$DELIM$'\r
Content-Disposition: form-data; name="example"\r
\r
test\r
'--$DELIM--$'\r
'

Answer 7

This is for multipart/form-data request method. for uploading a file add --form filename="@path/image.jpg;type=image/jpeg"

curl --form key="value" --form key="value" http://localhost:3000/test