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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).
perl v5.34.0 2023-11-23 Term::ReadLine(3perl)
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