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In learning this shell certain terminology is used to describe
commands and arguments. If you don't know the following terms and
definitions, becoming familiar with them will help you understand
later descriptions. - argument
and parameter
The words following a command or program name used
to pass information to that command or program. an argument is given
to a command. In the example, lp file1, file1 is
the argument and lp is
the command. a parameter is something that has a value (possibly
null or empty). In the example, X=12,
X is a parameter.
"variable" and "parameter" are usually interchangeable.
- blank
A tab or space character. Sometimes called a whitespace
character. - command
A subset of word. A word
is a command if it is the first word in a command line that is not
a redirection or variable assignment. - metacharacter
One of the following characters: ;,
&, (,
), |,
<, >,
newline, space, and tab. - option or flag
A letter preceded by a dash (-)
and separated from the command name by a blank. For example: -v - word
A sequence of characters separated by one or more
nonquoted metacharacters or whitespace. For example: date.
The five types of words the shell understands are: reserved words
(such as for),
built-in command names (such as pwd),
alias (such as type),
functions, and utility names (such as a path name). - simple command or command
line
A sequence of blank-separated words which may be
include options and parameters. The first word specifies the name
of the command to be executed. For example: cat -v filename A command line may contain many simple commands. In the command
line, cat file; rm file; who,
the three simple commands are cat file,
rm file, and
who. - identifier or name
A sequence of letters, digits, or underscores starting
with a letter or underscore. Identifiers are used as names for aliases,
functions, and named parameters. For example: new_program_1 - pipeline
A sequence of one or more commands separated by
the metacharacter |
which is called a pipe. For example: ls | file_list | print_script - list
A sequence of one or more pipelines separated by
;, &,
&&, or
||, and optionally
terminated by ;,
&, or |&.
For example: (sort -o temp; pr temp | lp; rm temp)&
Conventions | |
The following font conventions are used throughout this tutorial.
Title indicates
manual names and references to manual pages in the HP-UX
Reference. For example, "see date(1)
in the HP-UX Reference". Replaceable is used for
symbolic items representing parameters or variables typed by the
user. Emphasis is used for general
emphasis. Term is used when a word
is first introduced or defined. Computer
indicates a literal that must be typed exactly as shown, or text
as it is displayed by the system. For example: findstr prog.c > prog.str Note, when a command or file name is a literal, it is shown
in computer and not replaceable.
However, if the command or file name is symbolic (but not literal),
it is shown in replaceable as shown here: alias new_command=command_line In this case you would type in your own command_line
and new_command. Computer
also indicates file names, HP-UX commands, system calls, subroutines,
and path names. In a syntax statement, brackets ([ ]) designate
optional parameters; ellipses (...) designate optional repetition
of the word or parameter directly preceding them. In the following example, path
is an optional parameter to the cd
utility. Environment variables such as EDITOR
or PATH are represented in uppercase
characters, an HP-UX convention. A keycap, such as Return,
designates the pressing of that key. If the keycaps are connected
by a hyphen, press the first key down and hold it while pressing
the second key. For example: Unless otherwise stated, all references, such as
"see the env(1) entry for more details",
refer to entries in the HP-UX Reference.
If you cannot find an entry where you expect it to be, use the HP-UX
Reference index.
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