Author: tom

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Bash cheat sheet: Top 25 commands and creating custom commands

https://www.educative.io/blog/bash-shell-command-cheat-sheet

How to create your own custom Bash commands

Custom commands in Bash are known as “aliases”. Aliases are essentially an abbreviation, or a means to avoid typing a long command sequence. They can save a great deal of typing at the command line so you can avoid having to remember complex combinations of commands and options. There is one caveat to using aliases, and that is to be sure you don’t overwrite any keywords.

  • Syntax: alias alias_name = “command_to_run”

A very simple example would look like this:

alias c = “clear”

Now every time you want to clear the screen, instead of typing in clear, you can just type c and you’ll be good to go.

You can also get more complicated, such as if you wanted to set up a web server in a folder:

alias www = ‘python -m SimpleHTTPServer 8000’

Here’s an example of a useful alias for when you need to test a website in different web browsers:

alias ff4 = ‘/opt/firefox/firefox’

alias ff13 = ‘/opt/firefox13/firefox’

alias chrome = ‘/opt/google/chrome/chrome’

Apart from creating aliases that make use of one command, you can also use aliases to run multiple commands such as:

alias name_goes_here = ‘activator && clean && compile && run’

While you can use aliases to run multiple commands, it’s recommended that you use functions as they’re considerably more flexible and allow you to do more complex logic and are great for writing scripts.

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Python

Scripting

python3 -m http.server –help

pi@wordpress:~ $ python3 -m http.server –help
usage: server.py [-h] [–cgi] [–bind ADDRESS] [–directory DIRECTORY] [port]

positional arguments:
  port                  Specify alternate port [default: 8000]

optional arguments:
  -h, –help            show this help message and exit
  –cgi                 Run as CGI Server
  –bind ADDRESS, -b ADDRESS
                        Specify alternate bind address [default: all
                        interfaces]
  –directory DIRECTORY, -d DIRECTORY
                        Specify alternative directory [default:current
                        directory]

python -m http.server 8000 --bind 127.0.0.1

pi@wordpress:~ $ ls
environments
pi@wordpress:~ $ cd environments/
pi@wordpress:~/environments $ source my_env/bin/activate
(my_env) pi@wordpress:~/environments $ ls my_env/
bin  include  lib  pyvenv.cfg  share
(my_env) pi@wordpress:~/environments $ deactivate                                   pi@wordpress:~/environments $

Python3 variant that echoes back the request headers to the sender as response headers and body

serve.py

#!/usr/bin/env python3

from http.server import SimpleHTTPRequestHandler
from socketserver import TCPServer
import logging
import sys

try:
    PORT = int(sys.argv[1])
except:
    PORT = 8000

class GetHandler(SimpleHTTPRequestHandler):

    def do_GET(self):
        self.send_response(200, self.headers)
        for h in self.headers:
            self.send_header(h, self.headers[h])
        self.end_headers()


Handler = GetHandler
httpd = TCPServer(('', PORT), Handler)

httpd.serve_forever()

Usage:

$ python3 serve.py

OR

$ python3 serve.py <PORT>

Sample response from curl:

$ curl -v localhost:8000 -H "Host: blah.com"
* Connected to localhost (127.0.0.1) port 8000 (#0)
> GET / HTTP/1.1
> Host: blah.com
> User-Agent: curl/7.71.1
> Accept: */*
>
* Mark bundle as not supporting multiuse
* HTTP 1.0, assume close after body
< HTTP/1.0 200 Host: blah.com
< User-Agent: curl/7.71.1
< Accept: */*
<

Server: SimpleHTTP/0.6 Python/3.7.7
Date: Fri, 03 Jul 2020 01:52:09 GMT
Host: blah.com
User-Agent: curl/7.71.1
Accept: */*

* Closing connection 0