Term::ReadLine(3perl) Perl Programmers Reference Guide Term::ReadLine(3perl)
NAME
Term::ReadLine - Perl interface to various "readline" packages. If no
real package is found, substitutes stubs instead of basic functions.
SYNOPSIS
use Term::ReadLine;
my $term = Term::ReadLine->new('Simple Perl calc');
my $prompt = "Enter your arithmetic expression: ";
my $OUT = $term->OUT || \*STDOUT;
while ( defined ($_ = $term->readline($prompt)) ) {
my $res = eval($_);
warn $@ if $@;
print $OUT $res, "\n" unless $@;
$term->addhistory($_) if /\S/;
}
DESCRIPTION
This package is just a front end to some other packages. It's a stub to
set up a common interface to the various ReadLine implementations found
on CPAN (under the "Term::ReadLine::*" namespace).
Minimal set of supported functions
All the supported functions should be called as methods, i.e., either as
$term = Term::ReadLine->new('name');
or as
$term->addhistory('row');
where $term is a return value of Term::ReadLine->new().
"ReadLine" returns the actual package that executes the commands. Among
possible values are "Term::ReadLine::Gnu",
"Term::ReadLine::Perl", "Term::ReadLine::Stub".
"new" returns the handle for subsequent calls to following
functions. Argument is the name of the application.
Optionally can be followed by two arguments for "IN" and
"OUT" filehandles. These arguments should be globs.
"readline" gets an input line, possibly with actual "readline" support.
Trailing newline is removed. Returns "undef" on "EOF".
"addhistory"
adds the line to the history of input, from where it can be
used if the actual "readline" is present.
"IN", "OUT" return the filehandles for input and output or "undef" if
"readline" input and output cannot be used for Perl.
"MinLine" If argument is specified, it is an advice on minimal size of
line to be included into history. "undef" means do not
include anything into history. Returns the old value.
"findConsole"
returns an array with two strings that give most appropriate
names for files for input and output using conventions
"<$in", ">out".
The strings returned may not be useful for 3-argument
open().
Attribs returns a reference to a hash which describes internal
configuration of the package. Names of keys in this hash
conform to standard conventions with the leading "rl_"
stripped.
"Features" Returns a reference to a hash with keys being features
present in current implementation. Several optional features
are used in the minimal interface: "appname" should be
present if the first argument to "new" is recognized, and
"minline" should be present if "MinLine" method is not
dummy. "autohistory" should be present if lines are put
into history automatically (maybe subject to "MinLine"), and
"addhistory" if "addhistory" method is not dummy.
If "Features" method reports a feature "attribs" as present,
the method "Attribs" is not dummy.
Additional supported functions
Actually "Term::ReadLine" can use some other package, that will support
a richer set of commands.
All these commands are callable via method interface and have names
which conform to standard conventions with the leading "rl_" stripped.
The stub package included with the perl distribution allows some
additional methods:
"tkRunning" makes Tk event loop run when waiting for user input (i.e.,
during "readline" method).
"event_loop"
Registers call-backs to wait for user input (i.e., during
"readline" method). This supersedes tkRunning.
The first call-back registered is the call back for waiting.
It is expected that the callback will call the current event
loop until there is something waiting to get on the input
filehandle. The parameter passed in is the return value of
the second call back.
The second call-back registered is the call back for
registration. The input filehandle (often STDIN, but not
necessarily) will be passed in.
For example, with AnyEvent:
$term->event_loop(sub {
my $data = shift;
$data->[1] = AE::cv();
$data->[1]->recv();
}, sub {
my $fh = shift;
my $data = [];
$data->[0] = AE::io($fh, 0, sub { $data->[1]->send() });
$data;
});
The second call-back is optional if the call back is
registered prior to the call to $term->readline.
Deregistration is done in this case by calling event_loop
with "undef" as its parameter:
$term->event_loop(undef);
This will cause the data array ref to be removed, allowing
normal garbage collection to clean it up. With AnyEvent,
that will cause $data->[0] to be cleaned up, and AnyEvent
will automatically cancel the watcher at that time. If
another loop requires more than that to clean up a file
watcher, that will be up to the caller to handle.
"ornaments" makes the command line stand out by using termcap data. The
argument to "ornaments" should be 0, 1, or a string of a
form "aa,bb,cc,dd". Four components of this string should
be names of terminal capacities, first two will be issued to
make the prompt standout, last two to make the input line
standout.
"newTTY" takes two arguments which are input filehandle and output
filehandle. Switches to use these filehandles.
One can check whether the currently loaded ReadLine package supports
these methods by checking for corresponding "Features".
EXPORTS
None
ENVIRONMENT
The environment variable "PERL_RL" governs which ReadLine clone is
loaded. If the value is false, a dummy interface is used. If the value
is true, it should be tail of the name of the package to use, such as
"Perl" or "Gnu".
As a special case, if the value of this variable is space-separated, the
tail might be used to disable the ornaments by setting the tail to be
"o=0" or "ornaments=0". The head should be as described above, say
If the variable is not set, or if the head of space-separated list is
empty, the best available package is loaded.
export "PERL_RL=Perl o=0" # Use Perl ReadLine sans ornaments
export "PERL_RL= o=0" # Use best available ReadLine sans ornaments
(Note that processing of "PERL_RL" for ornaments is in the discretion of
the particular used "Term::ReadLine::*" package).
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