ftp.barnyard.co.uk/2015.02.ftp.barnyard.co.uk.tar/ftp.barnyard.co.uk/robot-pd/12400.ZIP/12400B.DSK/manual02.txt

Text File | 1998-04-30 | 13KB | 427 lines

                 C H A P T E R    T W O

                   Command Dictionary

2.1 Shell Phraseology

<directory path>

This is a sequence of characters describing  the  location
of a directory to the Shell. There are three methods  that
the Shell recognises, which were described in chapter  one
of this manual.

<file path>

A file path is a directory path with a file name specified
after the directory path. The file name is appended to the
directory path and separated by a single slash ('/'),  but
no spaces.

<selector>

Some commands can operate in different ways. Such commands
allow the user to  tailor  their  operation  by  selecting
options.  These  options  are  invoked  by  the   use   of
"selectors". In general these are a sequence of characters
prefixed by "&". Details are given for each command  where
such selectors exist.

[RETURN] indicates that the key  marked  RETURN  or  ENTER
should be pressed.

2.2 Internal Commands

Internal commands are commands which exist as part of  the
main operating system code. As such, they do not  need  to
be  loaded  from  the  disc,  and  hence  execute   almost
immediately. Another advantage is that the commands can be
executed as subroutines to other commands, or from  within
transient programs such as text editors. They are  usually
very common or useful routines.


2.2.1 The CD command

Description :Change Directory

Format :CD <directory path>

Changes  the  position  (or  location)  of   the   working
directory within the tree structure. The working directory
is used for specifying relative path names. A  good  habit
to get into is creating a directory for  every  topic  the
computer is used for. When dealing with that topic, use CD
to move into the related directory.

If the <directory path> is not given,  the  user  will  be
returned to their home directory.

CD can be abbreviated by  simply  entering  the  directory
path followed by a colon:-

1>CD /COM --> 1>/COM:

Example:1>CD [RETURN]
This makes your home directory the current directory. This
places you in the same position as when you first  started
the session.


2.2.2 The LF command

Description :List Files

Format :LF [<directory path>]

Lists the contents of the given directory, or the  working
directory if no directory path is  given.  The  files  are
listed in the following format:-

<Directory path>

DRIVE {<A:><B:>} USER <1 .. 15>

[++<<File name><size>>]

[++<subdirectory>]

Example:1>LF /COM
Lists the contents of the COMmand directory. These are  the
system program files for external commands.


2.2.3 The PWD Command

Description :Print Working Directory.

Format :PWD

Prints the absolute path to the  working  directory.  This
command can't be abbreviated (see ALIAS).


2.2.4 The CAT command

Description :ConCATenate.

Format :CAT ++<[<selector>] <file path>>

Outputs the contents of the given files to  the  VDU.  The
listing will be  paused  after  a  window  full  has  been
displayed. Pressing [SPACE] will  enable  the  listing  to
continue. If several files are specified, there will be no
break between the display of each file in the sequence.

As mentioned above, CAT will usually operate even if it is
sending the results to a screen window of smaller size. If
paging does not appear to be correct, however, ^S  can  be
pressed to pause the display, and ^Q to restart it.

Note that while CAT  will  display  the  contents  of  the
object file produced by the COMP program (see  later)  the
contents will not be displayed correctly. This is  because
such files  are  stored  as  true  ASCII-rather  than  the
TEXT format used by Centrox.

If the selector "A" is given then the following file  will
be treated as a true ASCII file. This allows  object  code
produced by COMP to be listed. Note that the "A"  selector
only holds for one file-it must be  invoked  before  EVERY
file path that requires  it  if  several  file  paths  are
given.

Note  that  due  to  memory  restrictions,  CAT  does  NOT
translate the  backward  single  quote  character  into  a
double quote character and hence text files may look odd.

Example:1>CAT -/login.usr
This lists the contents of your login file.  The  commands
that are shown by this command will be executed as soon as
Centrox is able, and before you type your first command.

         :2>CAT &A ascii1.dat text.dat &A ascii2.dat
Lists an ASCII file, followed by a text file and  finishes
by listing another ASCII file.


2.2.5 The DATE Command

Format :Date [<date><month><year>]

Takes the given date - or the current  date  if  none  was
given - and works out the day that the date  occurred  on.
The result is then output in the following form:-

              <day>, <month> <date> <year>

Note that the date is given to the  routine  as  a  number
whilst the month may be given numerically or literally. In
the resulting output, the day is given  literally,  as  is
the month.  The  year,  of  course,  is  always  input-and
output-numerically.

The system used to calculate the date takes  into  account
the various "modifications" made to the calendar. It works
out the date according to the Protestant  version  of  the
Julian calendar.

The routine used by  the  Shell  was  first  published  in
Amstrad Action. The source code from which the routine was
derived was written by Gary Nugent and  published  in  the
July '87 issue of Amstrad Action.

Note that the Shell will ask the user to set  the  correct
date when signing on, failure to set  the  date  correctly
will not "upset" the system  but  since  an  illegal  date
can't be entered, there is little point  in  not  entering
the date correctly-the facility was provided for the user,
not the machine.

Example:1>DATE 28 2 1967
          2>DATE 28 February 1967
          3>D. 28 F. 1967
These all show the same information..the day  that  I  was
born,  Tuesday,  February  the   28th   1967.   Note   the
abbreviations employed in the third example.

Error Messages

"Illegal date"-The date you supplied was not legal.

"No such date"-The date you supplied  is  legal,  but  was
removed when the protestants corrected the calendar.

"The date is:<date>"-Standard reply.


2.2.6 The TIME Command

Format :TIME

Displays  the  current  time  on  the  VDU.  The  time  is
displayed in the following format:-

                     <hour>:<minute>

Note that the Shell will request the user to set the  time
while signing on.

Note that the Shell will "ring" the  chimes  on  the  hour
using the chime bell (see ECHO). As with the DATE command,
incorrect setting of the time is not a problem, however an
illegal time will be rejected.

If the Shell is left in direct command mode for more  than
about 2 hours, its internal clock will lose time. If  left
in direct mode for any length of time, there will also  be
a slight delay after RETURN is pressed, while the clock is
updated.

This command can't be abbreviated (see ALIAS).

Error Messages

"The time is:<time>"-Standard report.


2.2.7 The DO Command

Format :DO [{<number><string>}]

The Shell remembers the last twenty commands,  and  allows
the user to recall them to save time. The  DO  command  is
the main mechanism for command line recall.  It  works  in
two ways:-

1.DO <number>

The Shell numbers each command line as it is entered.  The
current number will usually be displayed when the Shell is
waiting for some input. Using DO as above will recall  the
command line that had the given number. See ECHO.

2.DO <string>

Will search through the  stored  commands  looking  for  a
command line that begins with the given string. Note  that
the search begins at the most recently typed command line.

In either case, note that a command line  may  consist  of
several commands, separated by semi-colons. Also note that
only those commands entered at the Shell  prompt  will  be
stored. Programs that allow access to the  Shell  routines
are unlikely to update the list, though they may  well  be
allowed to recall command lines.

If no argument is passed to the command,  a  list  of  the
currently  stored  commands  will  be  displayed  in   the
following format:-

             <command.number> <command.line>

Error Messages

"Command lost"-The Shell can't find the requested command.


2.2.8 The ALIAS Command

Format :ALIAS [<word>[/<phrase>]]

The Shell can be programmed to substitute the  first  WORD
in a statement for a PHRASE. The phrase may  both  contain
any number of characters. The shell removes the word  from
the statement and replaces it with the phrase.

If only  <word>  is  given,  the  Shell  will  delete  the
instruction for replacing occurrences of <word>.

If no phrases are given, the Shell will list the currently
defined instructions.

To  allow  multiple  commands  to  be   substituted,   the
semicolon will need to be inhibited. This can be  done  by
typing a pair of semicolons:-

   ALIAS ebl/echo Editing Login file;;ctx -/login.usr

Several internal  commands  are  created  using  ALIAS  in
conjunction with ECHO (see later). These commands are:-

TIME:ALIAS time/ECHO The time is:!t!c0A!c0d

PWD:ALIAS pwd/The working directory is:!w!c0A!c0D

Also MODE & CLS, which are  covered  later.  Creating  the
commands this way makes  more  efficient  use  of  memory.
Unfortunately it does mean that these  commands  can't  be
abbreviated.

It can save typing effort if you create your own  commands
to move into often used directories, eg:-

  ALIAS ebl/ECHO Moving into source directory;;cd -/ebl

Note that when ALIAS is used in a login file,  any  double
semicolons should be replaced by a single semicolon, since
the login interpreter  does  not  allow  multiple  command
statements, and hence does not recognise  the  delimiting
abilities of the semicolon.

ALIAS does not distinguish between upper  and  lower  case
letters.

Error Messages

"No room"-No more ALIASes can be defined.


2.2.9 The ECHO Command

Format :ECHO <CXtring>

Passes (reads  and  evaluates)  the  given  "CXtring"  and
outputs the result  on  the  VDU.  This  command  is  very
powerful as the CXtring can contain meta characters, which
are prefixed by "!" ("Pling").

Echo  has  several  uses.  Firstly,  it  can  be  used  in
conjunction with a LOGIN file to display sign on messages,
it is also used to display the time and  can  be  used  in
conjunction with ALIASed commands to  let  the  user  know
what a particular ALIAS is doing.

The Meta characters allowed are:-

"w" : Output working directory.
"!" : Outputs a `!'.
"d" : Outputs the current date.
"t" : Outputs the current time.
"u" : Outputs the current user's name.
"c"<00.FF> : Outputs the character whose  ASCII  code   is
given in hexadecimal. The sequence !c0A!c0D will  start  a
new line on the screen.
"$"<0..99><char.> Outputs the given number  of  the  given
character.
"n" : Outputs the current prompt number - See DO.
"g" : "Ring" the chime bell. This bell is also rung on the
hour to sound the chimes.


2.2.10 The PROMPT Command

Format :PROMPT <CXtring>

The Shell can be programmed to  output  a  prompt  message
whenever it  is  expecting  a  command  line.  The  PROMPT
command allows the user to define this message.

The message is given as a CXtring, which is defined in the
entry on ECHO. If no CXtring is given, the prompt will not
appear.


2.2.11 The CLS Command

Format :CLS

This command clears the screen. CLS is  defined  with  the
ALIAS mechanism:-

ALIAS cls/ECHO !c0C

This command can't be abbreviated (see ALIAS).

2.2.12 The MODE Command

Format :MODE <number>

Again, this is defined using ALIAS, using a clever trick:-

ALIAS mode/ECHO !c04!c

This command can't be abbreviated (see ALIAS).

Note that the construct !c <digit> is quite  valid,  and
hence the above command works.


2.2.13 The ENLARGE Command

Format :ENLARGE [<command statement>]

This command toggles the Shell residency between Transient
and Permanent (the default). When the Shell is  transient,
it is usually only present when it is needed.

The advantage gained from Transient mode is that you  have
an extra 7K of memory available. The disadvantage is  that
Shell commands are no longer accessible  from  within  TPs
(such as the text editor),  and  returning  to  the  Shell
prompt after completion of an external command takes a few
seconds longer.

If the <command statement> is given, the Shell  will  only
be removed for the duration of the given command.


2.2.14 PATH

Syntax :PATH ++<Directory path>

Lists the directories in which the Shell is to  look  when
an external command is issued if the external  command  is
not found in one of  these  directories,  then  the  error
message "<name> ?" is issued. Note the the path "/COM"  is
always searched, and  that  the  Shell  defaults  to  also
searching "." (the current directory).

 A P T E R    T W OΩ

                   ╔Command DictionaryΘ

╩2.1 Shell PhraseologyΩ

╔<director