Get a Single Header with cURL

By  on  

Debugging third party apps can be difficult for a variety of reasons.  You take for granted that the third party has not only properly coded their app but that their server is also serving files properly.  As more a developer than a sysadmin I tend to spend a long time on the code before I ensure the server stuff is correct.  One mistake often made on the server side is not sending correct Content-Type headers with content, especially audio and video files, and that can cause a real problem for the app or codec trying to do something with the content.  These days I check response headers before I do anything else.

Getting complete response headers with cURL is easy:

#  Get response headers
curl -I https://davidwalsh.name

#  Result:
#  HTTP/1.1 301 Moved Permanently
#  Date: Wed, 03 Feb 2016 17:29:51 GMT
#  Content-Type: text/html; charset=iso-8859-1
#  Connection: keep-alive
#  Set-Cookie: __cfduid=dab1e532a38b35ce7d764344217ddd8dc1454520590; expires=Thu, 02-Feb-17 17:29:50 GMT; path=/; domain=.davidwalsh.name; HttpOnly
#  Location: https://davidwalsh.name/
#  Cache-Control: max-age=1
#  Expires: Wed, 03 Feb 2016 17:29:52 GMT
#  Vary: Accept-Encoding
#  Server: cloudflare-nginx
#  CF-RAY: 26efdc3d2aa841ef-MSP

But that's a lot of info to sift through if you only want the one header.  Here's how you can retrieve just one header:

#  Get single header only
#  curl {url} -I | grep -Fi {header_name}
curl https://davidwalsh.name -I | grep -Fi Content-Type

#  Result:
#  Content-Type: text/html; charset=iso-8859-1

With the extra grep above you'll only get the one header back.  Simple!

Recent Features

  • 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...

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

Incredible Demos

  • By
    Control Element Outline Position with outline-offset

    I was recently working on a project which featured tables that were keyboard navigable so obviously using cell outlining via traditional tabIndex=0 and element outlines was a big part of allowing the user navigate quickly and intelligently. Unfortunately I ran into a Firefox 3.6 bug...

  • By
    Web Audio API

    The Web Audio API allows developers to load and decode audio on demand using JavaScript.  The more I evaluate awesome games for Firefox OS TVs, the more I get to learn about these APIs that I normally wouldn't touch.  The following is a very basic introduction to the WebAudio API...

Discussion

  1. Lev Nar

    this is the best answer that I found with my problem, but the only question i have is how to do this is curl php

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