When I attempt to list a directory using the 1s command I receive the line

-bash: 1s: command not found


The command starts with the letter L, not the number 1 or the letter I; it's short for list. The font you're using may make that confusing, in which case I would suggest changing to a different fixed-width font for your terminal. I personally am a fan of PragmataPro and Courier New, and you'll find Courier New installed on pretty much any Windows, Linux, or OS X system these days.

If you're having trouble with the fonts on a particular website when looking up help information for commands, you can try copying and pasting the command. Note that most terminals on Windows and Linux don't usually support Ctrl+V for pasting unless you play with the keybindings, but OS X does support the usual Cmd+V for pasting in its Terminal.app.

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