- NAME
- SYNOPSIS
- DESCRIPTION
- Minimal set of supported functions
- Additional supported functions
- EXPORTS
- ENVIRONMENT
- CAVEATS
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. 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 $term is a return value of Term::ReadLine->new().
ReadLinereturns the actual package that executes the commands. Among possible values are
Term::ReadLine::Gnu,Term::ReadLine::Perl,Term::ReadLine::Stub.newreturns the handle for subsequent calls to following functions. Argument is the name of the application. Optionally can be followed by two arguments for
INandOUTfilehandles. These arguments should be globs.readlinegets an input line, possibly with actual
readlinesupport. Trailing newline is removed. ReturnsundefonEOF.addhistoryadds the line to the history of input, from where it can be used if the actual
readlineis present.IN,OUTreturn the filehandles for input and output or
undefifreadlineinput and output cannot be used for Perl.MinLineIf argument is specified, it is an advice on minimal size of line to be included into history.
undefmeans do not include anything into history. Returns the old value.findConsolereturns an array with two strings that give most appropriate names for files for input and output using conventions
"<$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. FeaturesReturns a reference to a hash with keys being features present in current implementation. Several optional features are used in the minimal interface:
appnameshould be present if the first argument tonewis recognized, andminlineshould be present ifMinLinemethod is not dummy.autohistoryshould be present if lines are put into history automatically (maybe subject toMinLine), andaddhistoryifaddhistorymethod is not dummy.If
Featuresmethod reports a featureattribsas present, the methodAttribsis 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:
tkRunningmakes Tk event loop run when waiting for user input (i.e., during
readlinemethod).ornamentsmakes the command line stand out by using termcap data. The argument to
ornamentsshould 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.newTTYtakes 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().

