Macintosh Terminal Pocket Guide

What’s a Command?

OS X comes with over 1,000 commands for file manipulation, text editing, printing, mathematics, computer programming, typesetting, networking…you name it. A typical command is run in a shell by typing its program name, followed by options and arguments, like this:

wc -l myfile

The program name (wc, the “word count” program) refers to a program somewhere on your Mac that the shell will locate and run. Options, which usually begin with a dash, affect the behavior of the program. In the preceding command, the -l option tells wc to count lines and not words. The argument myfile specifies the file that wc should read and process.

Case Sensitivity

The commands in this book should be entered exactly, using the same capital (uppercase) and small (lowercase) letters we provide. In other words, commands are case-sensitive. If a command is wc -l (small “L”) but you type wc -L (capital “L”), it will not work.

In some situations, capital and small letters are equivalent. Specifically, the names of files and folders are case-insensitive, so when they appear on a command line, you can use capital or small letters as you see fit. Nevertheless, the rest of the command line is case-sensitive, so we recommend not changing the case of any letters in the presented commands.

Commands can have multiple options and arguments. Options may be given individually:

wc -l -w myfile           Two individual options

or combined behind a single dash:

wc -lw myfile             Same as -l -w

though some programs are quirky and ...