


Term::ReadLine(3pPerl Programmers Reference GuiTerm::ReadLine(3p)


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 = Term::ReadLine->new('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 = Term::ReadLine->new('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.



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Term::ReadLine(3pPerl Programmers Reference GuiTerm::ReadLine(3p)


       "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 "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 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



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Term::ReadLine(3pPerl Programmers Reference GuiTerm::ReadLine(3p)


                   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().



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