Hi there and welcome to my blog about computer science (CS). From time to time, you will find new posts on a broad range of CS topics.
Recently, I faced the issue that a I used a minimal Ubuntu VM on Azure to test that a web server is reachable.
Unfortunately, neither netcat nor telnet, wget or curl were installed - the only tools where I knew at that time to test the connectivity to a HTTP server.
This was unfortunate especially because I was in a debugging session with colleague from another department and even apt did somehow not work.
Later, I remembered that you can create a TCP connection via the file system. A here's the solution:
# Create a file descriptor in the running terminal that can both read from and write to the file located at
exec 3<>/dev/tcp/<hostname>/80
# Send the HTTP message to the file descriptor
printf "GET / HTTP/1.1\n\n" >&3
# Read the response from the file descriptor
cat <&3Copied and adapted from here: https://bash-prompt.net/guides/bash-sockets/
"So don't deceive yourself into thinking that a process will just solve a dysfunctional team's problems" - Billy Hollis
https://youtu.be/cADdwFk2-7U?t=3109
In the following video Jack Rusher talks about historical issues that influence how we build our software.
https://youtu.be/8Ab3ArE8W3s?t=1012
I think he's right in his critique. However, since these old-fashioned tools like (pseudo) ttys are still around, we should know them by heart until better options emerge.
https://www.haskell.org/ghcup/
curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | sh<command> 3>&1 1>&2 2>&3