Commands
Users communicate
with the Unix operating system by entering commands. Each
command is the name of a program to be executed.
Format
The format
of a Unix command is
<command> <-options> <arguments>
Options
are represented by letters of the alphabet and are preceded
by a hyphen (or minus sign). There should be no spaces between
the option letters and the hyphen. If the command takes an
argument- --a filename, for example---then the argument is
placed after the specification of the option(s). This order
is important. Commands will not necessarily have options or
arguments, but may have either or both. Remember that Unix
commands, options and arguments are all case-sensitive. Unix
commands themselves nearly always appear in lower case, as
do their options. However, there ARE some upper case options
to some commands. Therefore you should follow the format shown
exactly. In later sections of this document you will find
examples of commands with multiple options and multiple arguments.
Some Fundamental Commands
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Runs
the date program, which displays the time and
date on the screen.
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Counts
lines, words and characters in the file plants.
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Allows
you to start a "conversation" with another
current user, in this instance, Smith. Enter <CTRL/d>
to end the conversation.
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Full
screen method for sending messages to another user's
(here, Smith's) workstation.
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Makes
a record of everything printed on your screen during
a session. The default name for this file is typescript.
Use <CTRL/c> to exit from your script
session.
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Displays
in order the last 20 commands you have executed. Should
you want to re-enter a command, you can do so by typing
an exclamation point (known in Unix as bang), followed
by the command number. This can save a lot of typing
if the command line is long. Bang bang (two exclamation
points) will find and re-execute the last command
entered.
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Accesses
the "man page" entry for the command date.
This is Unix's on-line help system, which mimics printed
manual pages. Using man followed by the name
of the command you want help on will produce first
a depiction of the command's syntax, then a description
of its usage, then a listing of its options and their
functions, and then a notation of restrictions, if
any, on the command. Finally, man produces a cross-reference
to other related commands. Press the space bar to
advance through man page entries, or the character
Q to quit before you have reached the end.
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Followed
by a keyword (here, copy), this command prints out
a one-line synopsis of manual sections containing
that keyword. You can then turn to those manual sections
for full information. This is a means of determining
which commands are associated with which functions,
and is a good way of broadening your knowledge of
Unix.
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Entered
at the system prompt, this command severs your connection
to Unix. The key combination <CTRL/d> will also
log you out, as will logout.
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Control Sequences---Another
Type of "Command"
Commands
are not the only means of directing processing under Unix-
--control sequences are also available to generate a variety
of interrupts in a working environment. You will note that
entering a control sequence and executing it are simultaneous
occurrences, as there is no need to press <RETURN>.
To use a control sequence, press <CTRL>, and while you
are holding it down, press the character key for the sequence
you need.
Among the
most common Unix control sequences are:
<CTRL/d>
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Most
useful of all---logs you out if you are at the system
prompt, signals end of input, marks end of file.
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<CTRL/c>
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<CTRL/z>
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Suspends
the current job. Does not abort it, as on VMS systems.
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<CTRL/r>
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<CTRL/u>
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Erases
the contents of the current input line, allowing you
to start over.
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<CTRL/s>
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<CTRL/q>
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<CTRL/w>
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<CTRL/o>
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