perldoc > Term::ReadLine

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📛 NAME

Term::ReadLine - Perl interface to various "readline" packages. If no real package is found, substitutes stubs instead of basic functions.

🚀 Quick Reference

Use Case	Command	Description
📦 Create readline object	Term::ReadLine->new('name')	Returns handle for subsequent calls; optional IN/OUT filehandles
📝 Read a line	$term->readline($prompt)	Gets an input line, possibly with readline support; trailing newline removed
📜 Add to history	$term->addhistory($line)	Adds line to history for later recall
🎨 Set ornaments	$term->ornaments(0) or 1 or "aa,bb,cc,dd"	Control terminal standout for prompt/input
🔄 Event loop integration	$term->event_loop($wait_cb, $register_cb)	Register callbacks for waiting on input (e.g., AnyEvent, Tk)
🔧 Get filehandles	$term->IN / $term->OUT	Returns input/output filehandles or undef
⚙️ Check features	$term->Features	Returns hash of available features (appname, minline, autohistory, addhistory, attribs)

📝 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. Argument is the name of the application. Optionally can be followed by two arguments for "IN" and "OUT" filehandles (which 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 is the waiting callback; it will call the current event loop until there is something waiting on the input filehandle. The parameter passed in is the return value of the second callback. The second callback is for registration; the input filehandle (often STDIN) 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 by calling event_loop with "undef":

  $term->event_loop(undef);

This will cause the data array ref to be removed, allowing normal garbage collection. With AnyEvent, that will cause $data->[0] to be cleaned up, and AnyEvent will automatically cancel the watcher. 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 should be 0, 1, or a string of form "aa,bb,cc,dd" (four terminal capacities: first two for prompt standout, last two for input line standout).
• newTTY — Takes two arguments (input filehandle, 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 the 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).

📛 NAME 🚀 Quick Reference 📝 SYNOPSIS 📖 DESCRIPTION 🧩 Minimal set of supported functions ➕ Additional supported functions 📦 EXPORTS 🌍 ENVIRONMENT