This is especially useful for config files. Say you have a file like:

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cats = True
# cats = False

cat_names = ["Plop","Fluffy"]
#

Let’s say your desired output is:

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cats = True
cat_names = ["Plop","Fluffy"]

If this awesome stuff if all in a file called cats.cfg, you would run a command like:

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sed  's/#.*$//;/^$/d'  cats.cfg

Add in -i to make the changes in line in cats.cfg.

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sed -i 's/#.*$//;/^$/d'  cats.cfg

Example

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$ cat cats.cfg
cats = True
# cats = False

cat_names = ["Plop","Fluffy"]
#
$ sed  's/#.*$//;/^$/d'  cats.cfg 
cats = True
cat_names = ["Plop","Fluffy"]
$

The syntax varies depending on which version of nc you are using.

The older version:

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$ nc -v -z 127.0.0.1 443

The newer version:

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$ nc -v --recv-only 127.0.0.1 443

Mount an ISO file on your system at the specified mountpoint.

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$ mount -o loop /path/to/file.iso /my/mountpoint

The old Python 2 way of doing it:

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$ python -m SimpleHTTPServer

The Python3 approach:

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$ python3 -m http.server

Specify a custom port (8008) with the Python3 approach:

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$ python3 -m http.server 8008