Term::ReadLine
Term::ReadLine(3) Perl Programmers Reference Guide 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 = $term->OUT || \*STDOUT;
while ( defined ($_ = $term->readline($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. 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 $term is a return value of Term::ReadLine->new().
"ReadLine" returns the actual package that executes the commands.
Among possible values are "Term::ReadLine::Gnu",
"Term::ReadLine::Perl", "Term::ReadLine::Stub".
"new" returns the handle for subsequent calls to following func-
tions. Argument is the name of the application. Optionally
can be followed by two arguments for "IN" and "OUT" file-
handles. These arguments should be globs.
"readline" gets an input line, possibly with actual "readline" sup-
port. Trailing newline is removed. Returns "undef" on
"EOF".
"addhistory"
adds the line to the history of input, from where it can be
used if the actual "readline" is present.
"IN", "OUT" return the filehandles for input and output or "undef" if
"readline" input and output cannot be used for Perl.
"MinLine" If argument is specified, it is an advice on minimal size
of line to be included into history. "undef" means do not
include anything into history. Returns the old value.
"findConsole"
returns an array with two strings that give most appropri-
ate names for files for input and output using conventions
"<$in", ">out".
Attribs returns a reference to a hash which describes internal con-
figuration of the package. Names of keys in this hash con-
form 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 fea-
tures 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
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 addi-
tional 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 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 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 v5.8.6 2001-09-21 Term::ReadLine(3)
