Linux Pocket Guide, 2nd Edition

Reading This Book

We’ll describe many Linux commands in this book. Each description begins with a standard heading about the command; Figure 1-1 shows one for the ls (list files) command. This heading demonstrates the general usage in a simple format:

ls [options] [files]

which means you’d type “ls” followed, if you choose, by options and then filenames. You wouldn’t type the square brackets “[” and “]”: they just indicate their contents are optional; and words in italics mean you have to fill in your own specific values, like names of actual files. If you see a vertical bar between options or arguments, perhaps grouped by parentheses:

(file | directory)

This indicates choice: you may supply either a filename or directory name as an argument.

The special heading also includes six properties of the command printed in black (supported) or gray (unsupported):

Figure 1-1. Standard command heading

stdin

The command reads from standard input, i.e., your keyboard, by default. See Input and Output.

stdout

The command writes to standard output, i.e., your screen, by default. See Input and Output.

- file

When given a dash (-) argument in place of an input filename, the command reads from standard input; and likewise, if the dash is supplied as an output filename, the command writes to standard output. For example, the following wc command line reads the files file1 and file2, then standard input, then ...