> As it turns out, bash can speak HTTP by itself.

No, it can not. Bash lets you open TCP sockets.

What you are doing here is trying to speak HTTP yourself, which is fine for testing and debugging, and hella cool for fun to do by hand, but you will shoot yourself in the foot if you try to use this pseudo http client unattended in reality. This toy code does not parse HTTP properly and will break.

You could of course write a full http/1.1 client in bash, you can even do a full http server in pure bash: https://github.com/bahamas10/bash-web-server

For less insane, non-bash shells there is always nc which is usually probably the wiser choice.

At least on my systems there's also /dev/udp...

Neat, works against example.com

  exec 3<>/dev/tcp/example.com/80
  printf 'GET / HTTP/1.1\r\nHost: example.com\r\nConnection: close\r\n\r\n' >&3
  cat <&3

  HTTP/1.1 200 OK
  Date: Tue, 16 Jun 2026 17:37:45 GMT
  Content-Type: text/html
  ...

I ran into this while checking connectivity between containers on an internal Docker network where the image had neither curl nor wget.

The main surprise was that Bash has /dev/tcp which lets you do the equivalent of an HTTP request with a bit of shell magic, for instance:

  exec 3<>/dev/tcp/service/8642
  printf 'GET /health HTTP/1.1\r\nHost: service\r\nConnection: close\r\n\r\n' >&3
  cat <&3

Pretty cool!

A few years ago I had to do this for a SpringBoot health check from a Docker container:

FROM openjdk:11-jre-slim HEALTHCHECK --start-period=10s --timeout=3s --retries=5 \ CMD perl -e "use IO::Socket; $sock = IO::Socket::INET->new(Proto => 'tcp', PeerAddr => 'localhost', PeerPort => '8888') or die $@; $sock->autoflush(1); print $sock 'GET /actuator/health HTTP/1.1' . chr(0x0a) . chr(0x0d) . 'Host: localhost:8888' . chr(0x0a) . chr(0x0d) . 'Connection: close' . chr(0x0a) . chr(0x0d) . chr(0x0a) . chr(0x0d); while (my $line = $sock->getline ) { if ($line =~ /UP/) {exit;} }; close $sock; exit 1;"

It's interesting that most of the comments here are about using this feature to bypass security restrictions (whether valid or not). It says a lot about the attack surface of GNU utilities caused by featuritis.

This is pretty neat if all you need is to ping a local server but please use curl (or something equivalent) for contacting remote services. HTTP1.1 seems like such a simple protocol but in the real world you need to deal with proxies, different encodings, and redirects. Curl takes care of that (and a host of other annoying stuff) for you.

I discovered this bash trick by chance when I was once trying to healthCheck the Envoy's official OCI image container which didn't include curl or wget while forcing the envoy admin interface to listen on localhost which breaks the traditional k8s httpGet checks.

It was fun exploring this to make a native-shell-only peer-to-peer file transfer utility at work for some automation scripts. At least, it was until trying to replicate it in Powershell was somehow triggering Crowdstrike and the corporate Cybersecurity team thought I was writing malware.

Yes, it used to be my goto few times when some devices tried to lockdown everything with bare minimum core utils and no network capable tools like curl etc.

Reminds me of telnetting to port 80 to make a get request years and years ago

That's pretty neat, thanks for sharing

brb. recompiling bash in all my base images.

Reminds me of using telnet to port 80 to make get requests aeons ago