Provided by: libterm-shell-perl_0.04-1_all 
NAME
Term::Shell - A simple command-line shell framework.
SYNOPSIS
package MyShell;
use base qw(Term::Shell);
sub run_command1 { print "command 1!\n"; }
sub smry_command1 { "what does command1 do?" }
sub help_command1 {
<<'END';
Help on 'command1', whatever that may be...
END
}
sub run_command2 { print "command 2!\n"; }
package main;
my $shell = MyShell->new;
$shell->cmdloop;
DESCRIPTION
Term::Shell lets you write simple command-line shells. All the boring details like
command-line parsing, terminal handling, and tab completion are handled for you.
The base class comes with two commands pre-defined: exit and help.
To write a shell with an "exec" command, do something like this:
package MyShell;
use base qw(Term::Shell); # or manually edit @MyShell::ISA.
sub run_exec {
my ($o, $cmd, @args) = @_;
if ($cmd ne $0) {
print "I'm sorry you're leaving us...\n";
}
exec $cmd, @args;
exit 1;
}
When Term::Shell needs to handle the "exec" command, it will invoke this method. That's
all there is to it! You write handlers, and Term::Shell handles the gory details.
Using Term::Shell Shells
How do you bring your shell to life? Assuming the package "MyShell" contains your actions,
just do this:
use MyShell;
my $shell = MyShell->new;
# Setup code here (if you wish)
# Invoke the shell
$shell->cmdloop;
# Cleanup code here (if you wish)
Most people put the setup code in the shell itself, so you can usually get away with this:
use MyShell;
MyShell->new->cmdloop;
It's that simple! All the actions and command handlers go in "MyShell.pm", and your main
program is simple. In fact, it's so simple that some people like to write both the actions
and the invocation in the same file:
package main;
MyShell->new->cmdloop;
package MyShell;
use base qw(Term::Shell);
# Actions here
Adding commands to your shell is just as easy, if not easier.
Adding Commands to Your Shell
For every command "foo", Term::Shell needs a method called "run_foo()", where 'foo' is
what the user will type in. The method will be called with the Term::Shell object as the
first parameter, followed by any arguments the user typed after the command.
Several prefixes other than "run_" are supported; each prefix tells Term::Shell to call
that handler under different circumstances. The following list enumerates all the
"special" prefixes. Term::Shell will ignore any method that doesn't start with a prefix
listed here.
1. run_foo()
Adds the command "foo" to the list of supported commands. The method's return value is
saved by Term::Shell, but is not used.
The method is called with the Term::Shell object as its first argument, followed by
any arguments the user typed in.
Special case: if you provide a method "run_()", Term::Shell will call it whenever the
user enters a blank line. A blank line is anything which matches the regular
expression "/^\s*$/".
2. help_foo()
Adds the command "foo" to the list of help topics. This means the user may enter 'help
foo' and get a help screen. It should return a single string to be displayed to the
user.
The method is called with the Term::Shell object as its first argument, followed by
any arguments the user typed in after 'help foo'. You can implement hierarchical help
documents by using the arguments.
If you do not provide a "help_foo()" method, typing 'help foo' produces an error
message.
3. smry_foo()
Should return a one-line summary of "foo", to be displayed in the help screen.
This method is called with the Term::Shell object as its first argument, and no other
arguments.
If you do not provide a "smry_foo()" method, then the string 'undocumented' is used
instead.
4. comp_foo()
Provides custom tab-completion for "foo". That means if the user types 'foo ' and then
hits <TAB>, this method will be called. It should return an array reference containing
a list of possible completions.
This method is called with the Term::Shell object as its first argument, followed by
the three arguments:
1. $word
The word the user is trying to complete.
2. $line
The line as typed by the user so far.
3. $start
The offset into $line where $word starts.
If you do not provide "comp_foo()", Term::Shell will always return no completions for
"foo".
Special case: if you provide "comp_()", Term::Shell will call it when the user is
trying to complete the name of a command. Term::Shell provides a default "comp_()"
method, which completes the actions that you have written handlers for. If you want to
provide tab-completion for commands that do not have handlers, override "comp_()".
5. alias_foo()
Returns a list of aliases for "foo". When one of the aliases is used instead of "foo",
the corresponding handler for "foo" is called.
6. catch_run()
catch_help()
catch_comp()
catch_smry()
Called when an undefined action is entered by the user. Normally when the user enters
an unrecognized command, Term::Shell will print an error message and continue.
This method is called with the Term::Shell object, the command typed by the user, and
then the arguments which would normally be passed to the real handler.
The "catch_" methods may do anything the original function would have done. If you
want, you can implement all the commands in it, but that means you're doing more work
than you have to. Be lazy.
When you want something done right...
You sometimes have to do it yourself. Introducing add_handlers(). Naturally, it adds a
handler to the list of defined handlers in the shell.
Term::Shell can't always find the commands you want to implement by searching the
inheritance tree. Having an AUTOLOAD() method, for instance, will break this system. In
that situation, you may wish to tell Term::Shell about the extra commands available using
add_handlers():
package MyShell;
use base qw(Term::Shell);
sub AUTOLOAD {
if ($AUTOLOAD =~ /::run_fuzz$/) {
# code for 'fuzz' command
}
elsif ($AUTOLOAD =~ /::run_foozle$/) {
# code for 'foozle' command
}
}
sub init {
my $o = shift;
$o->add_handlers("run_fuzz", "run_foozle");
}
There are other ways to do this. You could write a "catch_run" routine and do the same
thing from there. You'd have to override "comp_" so that it would complete on "foozle" and
"fuzz". The advantage to this method is that it adds the methods to the list of commands,
so they show up in the help menu and you get completion for free.
Removing Commands from Your Shell
You're probably thinking "just don't write them". But remember, you can inherit from
another shell class, and that parent may define commands you want to disable. Term::Shell
provides a simple method to make itself forget about commands it already knows about:
1. remove_commands()
Removes all handlers associated with the given command (or list of commands).
For example, Term::Shell comes with two commands ("exit" and "help") implemented with
seven handlers:
1. smry_exit()
2. help_exit()
3. run_exit()
4. smry_help()
5. help_help()
6. comp_help()
7. run_help()
If you want to create a shell that doesn't implement the "help" command, your code
might look something like this example:
package MyShell;
use base qw(Term::Shell);
sub init {
my $o = shift;
$o->remove_commands("help");
}
# ... define more handlers here ...
2. remove_handlers()
Removes the given handler (or handlers) from the list of defined commands. You have to
specify a full handler name, including the 'run_' prefix. You can obviously specify
any of the other prefixes too.
If you wanted to remove the help for the "exit" command, but preserve the command
itself, your code might look something like this:
package MyShell;
use base qw(Term::Shell);
sub init {
my $o = shift;
$o->remove_handlers("help_exit");
}
# ... define more handlers here ...
Cover Your Tracks
If you do remove built in commands, you should be careful not to let Term::Shell print
references to them. Messages like this are guaranteed to confuse people who use your
shell:
shell> help
Unknown command 'help'; type 'help' for a list of commands.
Here's the innocuous looking code:
package MyShell;
use base qw(Term::Shell);
sub init {
my $o = shift;
$o->remove_commands("help");
}
MyShell->new->cmdloop;
The problem is that Term::Shell has to print an error message, and by default it tells the
user to use the "help" command to see what's available. If you remove the "help" command,
you still have to clean up after yourself and tell Term::Shell to change its error
messages:
1. msg_unknown_cmd()
Called when the user has entered an unrecognized command, and no action was available
to satisfy it. It receives the object and the command typed by the user as its
arguments. It should return an error message; by default, it is defined thusly:
sub msg_unknown_cmd {
my ($o, $cmd) = @_;
<<END;
Unknown command '$cmd'; type 'help' for a list of commands.
END
}
2. msg_ambiguous_cmd()
Called when the user has entered a command for which more than handler exists. (For
example, if both "quit" and "query" are commands, then "qu" is an ambiguous command,
because it could be either.) It receives the object, the command, and the possible
commands which could complete it. It should return an error message; by default it is
defined thusly:
sub msg_ambiguous_cmd {
my ($o, $cmd, @c) = @_;
local $" = "\n\t";
<<END;
Ambiguous command '$cmd': possible commands:
@c
END
}
The Term::Shell API
Shell classes can use any of the methods in this list. Any other methods in Term::Shell
may change.
1. new()
Creates a new Term::Shell object. It currently does not use its arguments. The
arguments are saved in '$o->{API}{args}', in case you want to use them later.
my $sh = Term::Shell->new(@arbitrary_args);
2. cmd()
cmd($txt);
Invokes $txt as if it had been typed in at the prompt.
$sh->cmd("echo 1 2 3");
3. cmdloop()
mainloop()
Repeatedly prompts the user, reads a line, parses it, and invokes a handler. Uses
"cmd()" internally.
MyShell->new->cmdloop;
mainloop() is a synonym for cmdloop(), provided for backwards compatibility. Earlier
(unreleased) versions of Term::Shell have only provided mainloop(). All documentation
and examples use cmdloop() instead.
4. init()
fini()
Do any initialization or cleanup you need at shell creation (init()) and destruction
(fini()) by defining these methods.
No parameters are passed.
5. preloop()
postloop()
Do any initialization or cleanup you need at shell startup (preloop()) and shutdown
(postloop()) by defining these methods.
No parameters are passed.
6. precmd()
postcmd()
Do any initialization or cleanup before and after calling each handler.
The parameters are:
1. $handler
A reference to the name of the handler that is about to be executed.
Passed by reference so you can control which handler will be called.
2. $cmd
A reference to the command as the user typed it.
Passed by reference so you can set the command. (If the handler is a "catch_"
command, it can be fooled into thinking the user typed some other command, for
example.)
3. $args
The arguments as typed by the user. This is passed as an array reference so that
you can manipulate the arguments received by the handler.
sub precmd {
my $o = shift;
my ($handler, $cmd, @args) = @_;
# ...
}
7. stoploop()
Sets a flag in the Term::Shell object that breaks out of cmdloop(). Note that
cmdloop() resets this flag each time you call it, so code like this will work:
my $sh = MyShell->new;
$sh->cmdloop; # an interactive session
$sh->cmdloop; # prompts the user again
Term::Shell's built-in run_exit() command just calls stoploop().
8. idle()
If you set "check_idle" to a non-zero number (see "The Term::Shell Object") then this
method is called every "check_idle" seconds. The idle() method defined in Term::Shell
does nothing -- it exists only to be redefined in subclasses.
package MyShell;
use base qw(Term::Shell);
sub init {
my $o = shift;
$o->{API}{check_idle} = 0.1; # 10/s
}
sub idle {
print "Idle!\n";
}
9. prompt_str()
Returns a string to be used as the prompt. prompt_str() is called just before calling
the readline() method of Term::ReadLine. If you do not override this method, the
string `shell> ' is used.
package MyShell;
use base qw(Term::Shell);
sub prompt_str { "search> " }
10. prompt()
Term::Shell provides this method for convenience. It's common for a handler to ask the
user for more information. This method makes it easy to provide the user with a
different prompt and custom completions provided by you.
The prompt() method takes the following parameters:
1. $prompt
The prompt to display to the user. This can be any string you want.
2. $default
The default value to provide. If the user enters a blank line (all whitespace
characters) then the this value will be returned.
Note: unlike ExtUtils::MakeMaker's prompt(), Term::Shell's prompt() does not
modify $prompt to indicate the $default response. You have to do that yourself.
3. $completions
An optional list of completion values. When the user hits <TAB>, Term::Shell
prints the completions which match what they've typed so far. Term::Shell does not
enforce that the user's response is one of these values.
4. $casei
An optional boolean value which indicates whether the completions should be
matched case-insensitively or not. A true value indicates that "FoO" and "foo"
should be considered the same.
prompt() returns the unparsed line to give you maximum flexibility. If you need the
line parsed, use the line_parsed() method on the return value.
11. cmd_prefix()
cmd_suffix()
These methods should return a prefix and suffix for commands, respectively. For
instance, an IRC client will have a prefix of "/". Most shells have an empty prefix
and suffix.
12. page()
page($txt)
Prints $txt through a pager, prompting the user to press a key for the next screen
full of text.
13. line()
line_parsed()
Although "run_foo()" is called with the parsed arguments from the command-line, you
may wish to see the raw command-line. This is available through the line() method. If
you want to retrieve the parsed line again, use line_parsed().
line_parsed() accepts an optional string parameter: the line to parse. If you have
your own line to parse, you can pass it to line_parsed() and get back a list of
arguments. This is useful inside completion methods, since you don't get a parsed list
there.
14. run()
If you want to run another handler from within a handler, and you have pre-parsed
arguments, use run() instead of cmd(). cmd() parses its parameter, whereas run() takes
each element as a separate parameter.
It needs the name of the action to run and any arguments to pass to the handler.
Term::Shell uses this method internally to invoke command handlers.
15. help()
If you want to get the raw text of a help message, use help(). It needs the name of
the help topic and any arguments to pass to the handler.
Term::Shell uses this method internally to invoke help handlers.
16. summary()
If you want to get the summary text of an action, use summary(). It needs the name of
the action.
Term::Shell uses this method internally to display the help page.
17. possible_actions()
You will probably want this method in comp_foo(). possible_actions() takes a word and
a list, and returns a list of possible matches. Term::Shell uses this method
internally to decide which handler to run when the user enters a command.
There are several arguments, but you probably won't use them all in the simple cases:
1. $needle
The (possible incomplete) word to try to match against the list of actions (the
haystack).
2. $type
The type with which to prefix $action. This is useful when completing a real
action -- you have to specify whether you want it to look for "run_" or "help_" or
something else. If you leave it blank, it will use $action without prefixing it.
3. $strip
If you pass in a true value here, possible_actions() will remove an initial $type
from the beginning of each result before returning the results. This is useful if
you want to know what the possible "run_" commands are, but you don't want to have
the "run_" in the final result.
If you do not specify this argument, it uses '0' (the default is not to strip the
results).
4. $haystack
You can pass in a reference to a list of strings here. Each string will be
compared with $needle.
If you do not specify this argument, it uses the list of handlers. This is how
Term::Shell matches commands typed in by the user with command handlers written by
you.
18. print_pairs()
This overloaded beast is used whenever Term::Shell wants to print a set of keys and
values. It handles wrapping long values, indenting the whole thing, inserting the
separator between the key and value, and all the rest.
There are lots of parameters, but most of them are optional:
1. $keys
A reference to a list of keys to print.
2. $values
A reference to a list of values to print.
3. $sep
The string used to separate the keys and values. If omitted, ': ' is used.
4. $left
The justification to be used to line up the keys. If true, the keys will be left-
justified. If false or omitted, the keys will be right-justified.
5. $ind
A string used to indent the whole paragraph. Internally, print_pairs() uses
length(), so you shouldn't use tabs in the indent string. If omitted, the empty
string is used (no indent).
6. $len
An integer which describes the minimum length of the keys. Normally, print_pairs()
calculates the longest key and assigns the column width to be as wide as the
longest key plus the separator. You can force the column width to be larger using
$len. If omitted, 0 is used.
7. $wrap
A boolean which indicates whether the value should be text-wrapped using
Text::Autoformat. Text is only ever wrapped if it contains at least one space. If
omitted, 0 is used.
8. $cols
An integer describing the number of columns available on the current terminal.
Normally 78 is used, or the environment variable COLUMNS, but you can override the
number here to simulate a right-indent.
19. term()
Returns the underlying "Term::ReadLine" object used to interact with the user. You can
do powerful things with this object; in particular, you will cripple Term::Shell's
completion scheme if you change the completion callback function.
20. process_esc()
This method may be overridden to provide shell-like escaping of backslashes inside
quoted strings. It accepts two parameters:
1. $c
The character which was escaped by a backslash.
2. $quote
The quote character used to delimit this string. Either """ or "'".
This method should return the string which should replace the backslash and the
escaped character.
By default, process_esc() uses escaping rules similar to Perl's single-quoted string:
1. Escaped backslashes return backslashes. The string "123\\456" returns "123\456".
2. Escaped quote characters return the quote character (to allow quote characters in
strings). The string "abc\"def" returns "abc"def".
3. All other backslashes are returned verbatim. The string "123\456" returns
"123\456".
Term::Shell's quote characters cannot be overridden, unless you override
line_parsed(): they are """ or "'". This may change in a future version of
Term::Shell.
21. add_handlers()
See "Adding Commands to Your Shell" for information on add_handlers().
22. remove_commands()
remove_handlers()
See "Removing Commands from Your Shell" for information on remove_handlers().
The Term::Shell Object
Term::Shell creates a hash based Perl object. The object contains information like what
handlers it found, the underlying Term::ReadLine object, and any arguments passed to the
constructor.
This hash is broken into several subhashes. The only two subhashes that a Shell should
ever use are $o->{API} and $o->{SHELL}. The first one contains all the information that
Term::Shell has gathered for you. The second one is a private area where your Shell can
freely store data that it might need later on.
This section will describe all the Term::Shell object "API" attributes:
The args Attribute
This an array reference containing any arguments passed to the Term::Shell constructor.
The case_ignore Attribute
This boolean controls whether commands should be matched without regard to case. If this
is true, then typing "FoO" will have the same effect as typing "foo".
Defaults to true on MSWin32, and false on other platforms.
The class Attribute
The class of the object. This is probably the package containing the definition of your
shell, but if someone subclasses your shell, it's their class.
The command Attribute
Whenever Term::Shell invokes an action, it stores information about the action in the
"command" attribute. Information about the last "run" action to be invoked is stored in
$o->{API}{command}{run}. The information itself is stored in a subhash containing these
fields:
name
The name of the command, as typed by the user.
found
The a boolean value indicating whether a handler could be found.
handler
The full name of the handler, if found.
Note that this facility only stores information about the last action to be executed. It's
good enough for retrieving the information about the last handler which ran, but not for
much else.
The following example shows a case where "run_foo()" calls "run_add()", and prints its
return value (in this case, 42).
sub run_foo {
my $o = shift;
my $sum = $o->run("add", 21, 21);
print "21 + 21 = ", $sum, "\n";
}
sub run_add {
my $o = shift;
my $sum = 0;
$sum += $_ for @_;
print "add(): sum = $sum\n";
return $sum;
}
At the end of run_foo(), $o->{API}{command}{run}{handler} contains the string "run_add".
The match_uniq Attribute
This boolean controls whether the user can type in only enough of the command to make it
unambiguous. If true, then if the shell has the commands "foo" and "bar" defined, the user
can type "f" to run "foo", and "b" to run "bar".
Defaults to true.
The readline Attribute
Which Term::ReadLine module is being used. Currently, this is always one of
"Term::ReadLine::Stub", "Term::ReadLine::Perl", or "Term::ReadLine::Gnu".
The script Attribute
The name of the script that invoked your shell.
The version Attribute
The version of Term::Shell you are running under.
BUGS AND DEFICIENCIES
There are bound to be some bugs lurking about.
If you find bugs, please send them to "NEILW@cpan.org".
SEE ALSO
For more information about the underlying ReadLine module, see Term::ReadLine. You may
also want to look at Term::ReadLine::Gnu and Term::ReadLine::Perl.
For more information about the underlying formatter used by print_pairs(), see
Text::Autoformat.
The API for Term::Shell was inspired by (gasp!) a Python package called "cmd". For more
information about this package, please look in the Python Library Reference, either in
your Python distribution or at http://www.python.org/doc/current/lib/module-cmd.html
AUTHOR
Neil Watkiss (NEILW@cpan.org)
COPYRIGHT
Copyright (c) 2001, Neil Watkiss. All Rights Reserved.
All Rights Reserved. This module is free software. It may be used, redistributed and/or
modified under the same terms as Perl itself.
See http://www.perl.com/perl/misc/Artistic.html