CURL in UNIX

cURL (client for URLs) is tool to transfer data using different protocols

curl is available on unix platform by default. It can also be used on windows with additional installation (e.g. git bash etc.). cURL can be used as a simple method to call REST APIs from command line. See man page of curl for more details.

This page uses github/NASA api for demo. Look for documentation of API needed to use curl. Most of the REST API docuemtation are created with curl example.

Sample curl requests:-

A simple example without any option. Default is GET request:- 

curl "https://api.github.com/users/kathuriaas"

GET request returning head details (-I or –head):- 

curl -I "https://api.github.com/users/kathuriaas"

GET request with passing query parameters:- 

curl -G -d 'api_key=DEMO_KEY' "https://api.nasa.gov/planetary/apod"

Above code is similar to:-

curl "https://api.nasa.gov/planetary/apod?api_key=DEMO_KEY"

More details for request and response headers can be viewed with -i (--include) and -v (--verbose) options.

Following options are useful when making an HTTP request to a server:-

  • -X, –request - (Specify a custom request method e.g. GET,POST to use when communicating with the HTTP server)
  • -H, –header - Send header information (e.g. “Content-Type: application/json”)
  • -d, –data - Sends the specified data (can be json data, if -H has content type as json)
  • -i, –include - Display response headers

POST request to create a github repo with token:- 

curl -i -H "Authorization: token <paste github token here>" -d '{"name":"test_github_api", "auto_init": true, "private": true,
"gitignore_template": "nanoc"}' "https://api.github.com/user/repos"

POST request to create a github repo with username & password:- 

curl -i -u "username:password" -d '{"name":"test_github_api", "auto_init": true, "private": true,
"gitignore_template": "nanoc"}' "https://api.github.com/user/repos"

Hide progress bar in a curl request:-

curl output can show progress which needs to be hidden, sometimes. This can be done with -s (--silent) option, as mentioned below:-

curl -s "https://api.github.com/users/kathuriaas"|python -c 'import sys,json;print (json.load(sys.stdin)["login"])'

Download a binary file using curl [use -o option]:- 

curl -o node-v12.18.0-linux-x64.tar.xz "https://nodejs.org/dist/v12.18.0/node-v12.18.0-linux-x64.tar.xz"

Save output to a file (with name as source file) using curl [use -O (--output) option]:- 

curl -O "https://api.github.com/users/kathuriaas"