term::readline(3)

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 = new Term::ReadLine 'Simple Perl calc';
my $prompt = "Enter your arithmetic expression: ";
my $OUT = $term->OUT || TDOUT;
while ( defined ($_ = $term->readline($prompt)) ) {
  my $res = eval($_), "0;
  warn $@ if $@;
  print $OUT $res, "0 unless $@;
  $term->addhistory($_) if /;
}

DESCRIPTION

This package is just a front end to some other packages.
At the moment this description is written, the only such
package is Term-ReadLine, available on CPAN near you. The
real target of this stub package is to set up a common
interface to whatever Readline emerges with time.

Minimal set of supported functions

All the supported functions should be called as methods,
i.e., either as

$term = new Term::ReadLine 'name';

or as

$term->addhistory('row');

where $term is a return value of Term::ReadLine->Init.

"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 his
tory. "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".

Attribs returns a reference to a hash which describes

internal configuration of the package. Names
of keys in this hash conform to standard con
ventions 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 min
imal 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 automat
ically (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 reacher 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).

"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 stand
out, 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 pack
age 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 "orna
ments=0". The head should be as described above, say

If the variable is not set, or if the head of space-sepa
rated list is empty, the best available package is loaded.

export "PERL_RL=Perl o=0" # Use Perl ReadLine with

out ornaments
export "PERL_RL= o=0" # Use best available Read

Line without ornaments

(Note that processing of "PERL_RL" for ornaments is in the
discretion of the particular used "Term::ReadLine::*"
package).

CAVEATS

It seems that using Term::ReadLine from Emacs minibuffer
doesn't work quite right and one will get an error message
like

Cannot open /dev/tty for read at ...

One possible workaround for this is to explicitly open
/dev/tty like this

open (FH, "/dev/tty" )

or eval 'sub Term::ReadLine::findConsole {

("&STDIN", "&STDERR") }';

die $@ if $@;
close (FH);

or you can try using the 4-argument form of Term::Read
Line->new().

perl v5.8.0 2002-06-01 Term::ReadLine(3)