POST Form Data with cURL

By  on  

cURL is the magical utility that allows developers to download a URL's contentexplore response headers, get stock quotes, confirm our GZip encoding is working, and much more.  One more great usage of cUrl for command line is POSTing form data to a server, especially while testing moderate to advanced form processing.  And just like other cURL commands, POSTing form data is incredibly simple.

POSTing Form Data with cURL

Start your cURL command with curl -X POST and then add -F for every field=value you want to add to the POST:

curl -X POST -F 'username=davidwalsh' -F 'password=something' http://domain.tld/post-to-me.php

If you were using PHP, you could use print_r on the $_POST variable to see that your server received the POST data as expected:

Array(
  'username' => 'davidwalsh',
  'password' => 'something'
)

If you need to send a specific data type or header with cURL, use -H to add a header:

# -d to send raw data
curl -X POST -H 'Content-Type: application/json' -d '{"username":"davidwalsh","password":"something"}' http://domain.tld/login

POSTing Files with cURL

POSTing a file with cURL is slightly different in that you need to add an @ before the file location, after the field name:

curl -X POST -F 'image=@/path/to/pictures/picture.jpg' http://domain.tld/upload

Using PHP to explore the $_FILES variable array would show file data as though it was uploaded via a form in browser:

Array(
  "image": array(
    "name" => "picture.jpg"
    "type" => "image/jpeg",
    "tmp_name" => "/path/on/server/to/tmp/phprj5rkG",
    "error" => 0,
    "size" => 174476
  )
)

POSTing file contents with cURL is Probably easier than you thought, right?

The first time I needed to POST file data from command line I thought I was in for a fight; instead I found that cURL made the process easy!

Recent Features

  • By
    6 Things You Didn’t Know About Firefox OS

    Firefox OS is all over the tech news and for good reason:  Mozilla's finally given web developers the platform that they need to create apps the way they've been creating them for years -- with CSS, HTML, and JavaScript.  Firefox OS has been rapidly improving...

  • By
    fetch API

    One of the worst kept secrets about AJAX on the web is that the underlying API for it, XMLHttpRequest, wasn't really made for what we've been using it for.  We've done well to create elegant APIs around XHR but we know we can do better.  Our effort to...

Incredible Demos

  • By
    Face Detection with jQuery

    I've always been intrigued by recognition software because I cannot imagine the logic that goes into all of the algorithms. Whether it's voice, face, or other types of detection, people look and sound so different, pictures are shot differently, and from different angles, I...

  • By
    Making the Firefox Logo from HTML

    When each new t-shirt means staving off laundry for yet another day, swag quickly becomes the most coveted perk at any tech company. Mozilla WebDev had pretty much everything going for it: brilliant people, interesting problems, awesome office. Everything except a t-shirt. That had to change. The basic...

Discussion

  1. zhat

    Very nice artice.! But can you explaint more about different from -d option and -F option in cURL.
    I was read in manual cURL is -d stand for --data, data when send to form will be endcode. But with -F ( stand for form ), it was really be encode ?
    Sorry my english.

  2. Ron

    Ok, I’m working with some hardware, which has an IP address “10.10.12.105”, I can download the file in “*.html” format and view the information. This information is in a table, and now I want to manually edit the information in the table and the upload the revised table back to my hardware.

    My cURL Code line for Downloading the file is:

    curl -o Camera_xw220.html http://root:Qwe16Sa7@10.10.12.105/oidtable.html
    

    My Revised File is located in

    C:\Users\123098765\Desktop\Camera_ff220-u.html
    

    How do I use the cURL to upload my revised “html” file, which is located on my PC?

  3. JL McKay

    Thanks for the article! I am posting this here because I scoured the internet for two days to track down an error I thought I had in curl and this is the top hit. It turned out that I never had an error – the -F and -d options both work fine. My problem was that I was pointing my curl POST request at a webpage, e.g., page.php, on which the only content was a form, form.php. Once I changed the request to point at form.php directly it worked like a charm. Dumb, silly error. Hope this saves someone else some time.

  4. Jin

    I keep on getting “curl: (35) error:0306E06C:bignum routines:BN_mod_inverse:no inverse”. Do you know how I can get around of this? Thanks

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!