When you see the command prompt
you can enter a command by typing the command
name and any options and arguments, followed by a carriage
return.
The default prompts are as follows - % for the C shell,
$ for the Korn shell and bash$ for the Bourne
Again shell; however, all these may be changed and frequently are.
The basic format of UNIX commands is:
command [-option(s)] [argument(s)]
Remember, UNIX is case-sensitive and therefore most UNIX commands must be entered in lower case.
The components are separated by at least one blank space. If an argument contains a blank, enclose the argument in double quote marks. Normally, options can be grouped (e.g., the -lw in the example below). Some options can have arguments, and unfortunately there isn't consistency on whether there should be a blank space between the option and its argument.
Examples:
wc -lw file1 file2
wc -l -w file1 file2
f77 -o outputfile program.f
In the third example outputfile is the
argument of the option -o.
You should be aware that UNIX commands are not noted for their
consistency of format.
Furthermore, commands, formats, arguments, and options
vary somewhat from one UNIX platform to another. In this Guide, we attempt
to be generic and describe options that are widely available; for exact details
on any command, including a full list of allowable options and arguments, see
the man pages for that command (the man command is described
in Section 
). Various options are possible to print man pages on a
printer but unfortunately there is no universal formula. You may try one of
the following but we cannot guarantee which will work best for you.
man pwd | col -b | lp -d dest
or groff -man file | lp -d dest
The first command pipes the output of the pwd man pages as an example to be
printed on a printer dest. The second command gives a better-formatted
output but you require know where the input man pages for the command in
question are stored. This will be somewhere in the /usr/man directory hierarchy.
You can guess where by looking at the output of man command: the
first line will contain the string command(i) and then the file in
question should be in /usr/man/mani/ command.1. Note that on some
systems, HP-UX for example, the files may only be in /usr/man/mani.Z and need
to be uncompressed before used in this way.
To correct typing errors you can use the erase key to erase character-by-character, or the kill key to kill an entire line. Recalling and editing previously-executed commands (command history) depends on the shell you are in and is discussed briefly in a later section.
More than one command can be entered on a line if the commands are separated by semicolons. Such commands will be executed sequentially.
If you need to continue a command to
a new line, you can either keep on typing or enter a backslash
character 
followed by a carriage return and then
continue on the next line.
You can use parentheses to group commands. Since a subshell is created for each group, this can be used to prevent changing the current environment. It can also be used to redirect all output from a set of commands considered as a group (see below).
Type ahead is permitted, even if the characters get interspersed with output.
UNIX commands are described online via the man command (see
section for more information).