UNIX command words and their arguments are shown exactly as you
should type them, including the distinction between uppercase
letters and lowercase letters, which are not interchangeable on
UNIX systems. For example, UNIX treats MAIL, Mail, and
as three distinct entities.
If an item is shown in italics,
substitute an appropriate real value for it, such as an
actual filename, user name, directory, or whatever.
If an item in a command syntax line is shown in square brackets
[ ], it's optional. Don't type the brackets in the command itself,
but do type any other punctuation shown, such as a hyphen.
If an ellipsis ... is shown, it means you can repeat the previous
item shown in the syntax line.
No command line is actually processed by the UNIX system until
you press the Return key. In most cases, this manual does not
show the Return.
Type control characters by holding down the key marked Control or
CTRL while you press another key. Control characters are
indicated in this manual with a caret character ^. For example,
^c means hold down the Control key while you press c.
The backspace key may be marked DEL, DELETE, RUB, or RUBOUT on
your keyboard. DEL is used here.
To illustrate the conventions, here is the format of the cp
command, which copies one or more files into a directory:
cp [-i] [-r] file ... directory
The command name cp
must be given in lower case; the -i
arguments may be omitted or given exactly as shown; then one or
more filenames of actual files; and finally an actual directory name.
Many punctuation characters and control characters have special
meaning to UNIX. Even before your first login, you should know the
ones below. Others are given in
Chapter 4, ``The Shell and Command Processing''.
Before you press the Return key, you can correct a typing error by
DEL to erase the previous character.
^w to erase the previous word.
^u to discard the whole command line.
If you are typing input to a process, press ^d to signal the end of
If you have used a VMS or DOS system, you may be familiar with typing
^z for this purpose, but on UNIX systems, ^z suspends a process: it
does not end input.
You can abort a process and discard its output by pressing ^c. You
can also discard output or skip over part of the display by using ^o.
When you do this, the program producing the output does not stop, but
its output is discarded until you give another ^o or until no more
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