cURL

cURL is a command line tool and library for transferring data with URLs. The command supports a number of different protocols, including HTTP, HTTPS, FTP, SCP, and SFTP. It is also designed to work without user interaction, like in scripts.

Note: Despite superficially equivalent to wget, this is not the case. See Can_I_do_recursive_fetches_with, run the equivalent curl command to a given wget command and What_is_curl_not.

Installation

Install the curl package.

Usage

Downloading

A common use case for cURL is to download the resource to a specified file:

$ curl --output filename URL

If the URL contains the file name, you can save the resource directly to a file of that name:

$ curl --remote-name URL

Similarly, you can use -J/--remote-header-name to accept a hint from an HTTP server (from the Content-Disposition header) for what the file should be named. If combined with -O/--remote-name, curl will use the file name specified by the URL if the HTTP server does not return a file name hint in its response.

Alternatively you can print the resource to stdout by omitting the output options:

$ curl URL

HTTP POST

You can use cURL to make HTTP POST requests:

$ curl --data 'request body' URL

If the request body cannot fit on the command line, cURL can read it from a file:

$ curl --data @filename URL

Sometimes, you may need to specify a custom value for the Content-Type header (cURL's default is application/x-www-form-urlencoded). You can do this with -H. For example, if you wanted to make a POST request with a JSON body:

$ curl --data 'json body' -H 'Content-Type: application/json' URL

note that curl also has a option to write post data in json and change those headers automatically: --json:

$ curl --json '{"key":"value"}' URL

Tips and tricks

Following redirects

To follow redirects (e.g. an HTTP to HTTPS redirect):

$ curl --location URL

Show download errors

By default curl would ignore errors (e.g. when downloading to a file, if there is a error curl would not notify you, and the file would be created empty) so use --fail to make it show a message on error:

$ curl --fail URL

Compression

If you want to transfer the data compressed, (e.g. in situations where bandwidth is more limited than CPU, curl would download the data compressed then uncompressed it after the download):

$ curl --compressed URL

ProgressBar

curl has option to a normal ProgressBar when it download files (e.g. [##### ] 80% )

$ curl --progress-bar URL

Globbing

You can also use globbing in curl:

$ curl "example.com/images/[1-9].png"
$ curl "example.com/{first_page,second_page,third_page}"

config file

curl also search for a config file called .curlrc in home directory and in $XDG_CONFIG_HOME. You can just put the command line argument you want to use with curl by default, for example :

$HOME/.curlrc

# this is a comment, the next line would be the option for progressbar:
-#
# to make curl always compress:
--compressed
# or just
compressed