There are references throughout this book to Linux utilities, shell commands (that is, commands that are part of a command shell itself), and system calls (Linux library functions). It's quite easy to confuse these three things, so I adopted a consistent way to differentiate them:
Formal descriptions of utilities, shell commands, and system calls are supplied in a box, using a modified-for-Linux Backus-Naur notation. The conventions of this notation are fairly simple and are described fully in the Appendix. As an example, here's a description of the Linux man utility:
Formal descriptions of all utilities, shell commands, system calls, and library functions used in the book are cross-referenced in the appendix. Regular references are included in the index. Sample Linux command sessions are presented in a Courier font. Keyboard input from the user is always displayed in italics, and annotations are always preceded by ellipses (. . .). Here's an example: $ ls ... generate a directory listing. myfile.txt yourfile.txt $ whoami ables $ _ ... a new prompt is displayed. |