Term::ReadLine(3pm) Perl Programmers Reference Guide Term::ReadLine(3pm)
NAME
Term::ReadLine - Perl interface to various "readline" packages. If no real package is found, substi-tutes substitutes
tutes 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 = $term->OUT || \*STDOUT;
while ( defined ($_ = $term->readline($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 = new Term::ReadLine 'name';
or as
$term->addhistory('row');
where $term is a return value of Term::ReadLine->new().
"ReadLine" returns the actual package that executes the commands. Among possible values are
"Term::ReadLine::Gnu", "Term::ReadLine::Perl", "Term::ReadLine::Stub".
"new" returns the handle for subsequent calls to following functions. Argument is the name of
the application. Optionally can be followed by two arguments for "IN" and "OUT" filehan-dles. filehandles.
dles. These arguments should be globs.
"readline" gets an input line, possibly with actual "readline" support. Trailing newline is removed.
Returns "undef" on "EOF".
"addhistory"
adds the line to the history of input, from where it can be used if the actual "readline"
is present.
"IN", "OUT" return the filehandles for input and output or "undef" if "readline" input and output
cannot be used for Perl.
"MinLine" If argument is specified, it is an advice on minimal size of line to be included into
history. "undef" means do not include anything into history. Returns the old value.
"findConsole"
returns an array with two strings that give most appropriate names for files for input
and output using conventions "<$in", ">out".
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 "Min-Line" "MinLine"
Line" 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 conven-tions conventions
tions 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
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 dis-able disable
able 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 pack-age package
age is loaded.
export "PERL_RL=Perl o=0" # Use Perl ReadLine without ornaments
export "PERL_RL= o=0" # Use best available ReadLine 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::ReadLine->new().
perl v5.8.8 2001-09-21 Term::ReadLine(3pm)
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