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Term::ReadLine - Perl interface to various readline packages.
If no real package is found, substitutes stubs instead of basic functions.
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/;
}
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).
All the supported functions should be called as methods, i.e., either as
$term = new Term::ReadLine 'name';
or as
$term->addhistory('row');
where $term is a return value of Term::ReadLine->new().
ReadLine
returns the actual package that executes the commands. Among possible
values are Term::ReadLine::Gnu, Term::ReadLine::Perl,
Term::ReadLine::Stub.
new
returns the handle for subsequent calls to following
functions. Argument is the name of the application. Optionally can be
followed by two arguments for IN and OUT filehandles. These
arguments should be globs.
readline
gets an input line, possibly with actual readline
support. Trailing newline is removed. Returns undef on EOF.
addhistory
adds the line to the history of input, from where it can be used if
the actual readline is present.
IN, OUT
return the filehandles for input and output or undef if readline
input and output cannot be used for Perl.
MinLine
If argument is specified, it is an advice on minimal size of line to
be included into history. undef means do not include anything into
history. Returns the old value.
findConsole
returns an array with two strings that give most appropriate names for
files for input and output using conventions "<$in", ">out".
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.
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 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.
None
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).
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().