Term::ReadLine(3pPerl Programmers Reference GuiTerm::ReadLine(3p)NAMETerm::ReadLine - Perl interface to various "readline" pack-
ages. 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.
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 $term is a return value of Term::ReadLine->new().
"ReadLine" returns the actual package that executes the
commands. Among possible values are
"Term::ReadLine::Gnu", "Term::ReadLine::Perl",
"Term::ReadLine::Stub".
"new" returns the handle for subsequent calls to fol-
lowing functions. Argument is the name of the
application. Optionally can be followed by two
arguments for "IN" and "OUT" filehandles. These
arguments should be globs.
"readline" gets an input line, possibly with actual "read-
line" support. Trailing newline is removed.
Returns "undef" on "EOF".
"addhistory"
adds the line to the history of input, from
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where it can be used if the actual "readline" is
present.
"IN", "OUT" return the filehandles for input and output or
"undef" if "readline" input and output cannot be
used for Perl.
"MinLine" If argument is specified, it is an advice on
minimal size of line to be included into his-
tory. "undef" means do not include anything
into history. Returns the old value.
"findConsole"
returns an array with two strings that give most
appropriate names for files for input and output
using conventions "<$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 conven-
tions 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 automati-
cally (maybe subject to "MinLine"), and "addhis-
tory" 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).
"ornaments" makes the command line stand out by using
termcap data. The argument to "ornaments"
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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 orna-
ments 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::*" pack-
age).
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
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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().
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