Golang : Check a web page existence with HEAD request example


Tags : golang client-head web-page-exist unsupported-protocol-scheme

There are times when we need to check if a web server is up and running first before querying further or simply want to check if a web page exists or not without downloading the HTML content. In this tutorial, we will learn how to utilize the HEAD request to ask for a response status from the web server without the response body. This also can be useful in a situation where we want to retrieve meta-information in the response headers, but without the response body.

The code example below will query a given URL from command line parameter and if the web page exists, it will return valid HTTP response codes such as OK, FOUND or MOVED PERMANENTLY. If the web page is not online, the program will panic and exit.

Pay attention to how some web servers handle HTTP differently from HTTPS. Depending on what you after, sometimes you need to query both HTTP and HTTPS version of a web page to determine their actual availability.

NOTE: If you get this error message unsupported protocol scheme "", make sure to put http or https before the domain name.

Here you go!


 package main

 import (
  "fmt"
  "net/http"
  "os"
 )

 func main() {

  if len(os.Args) != 2 {
 fmt.Printf("Usage : %s <URL> \n", os.Args[0])
 os.Exit(0)
  }

  url := os.Args[1]

  fmt.Println("Heading ", url)

  client := &http.Client{}

  resp, err := client.Head(url)

  if err != nil {
 fmt.Println(err)
 os.Exit(-1)
  }

  fmt.Println(url, " status is : ", resp.Status)

 }

Sample output:

$ ./headrequest https://www.facebook.com

Heading https://www.facebook.com

https://www.facebook.com status is : 200 OK

$ ./headrequest https://www.socketloop.com

Heading https://www.socketloop.com

https://www.socketloop.com status is : 200 OK

$ ./headrequest https://www.porkchop.com

Heading https://www.porkchop.com

Head https://www.porkchop.com: read tcp 192.168.1.69:33176->69.172.201.153:443: read: connection reset by peer

$ ./headrequest http://www.porkchop.com

Heading http://www.porkchop.com

http://www.porkchop.com status is : 200 OK

$ ./headrequest https://www.punyu.com

Heading https://www.punyu.com

Head https://www.punyu.com: x509: certificate is valid for *.asg.to, asg.to, not www.punyu.com

$ ./headrequest http://www.punyu.com

Heading http://www.punyu.com

http://www.punyu.com status is : 200 OK

Reference:

https://www.socketloop.com/references/golang-net-http-client-postform-function-example

  See also : Golang : Command line file upload program to server example



Tags : golang client-head web-page-exist unsupported-protocol-scheme

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


Advertisement