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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. It's a stub to set up a common interface to the vari-
       ous 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::Read-
                   Line::Gnu", "Term::ReadLine::Perl", "Term::ReadLine::Stub".

       "new"       returns the handle for subsequent calls to following functions. Argument is the name of the appli-
                   cation. 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".

       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 argu-
                   ment 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 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 file-
                   handles.

       One can check whether the currently loaded ReadLine package supports these methods by checking for correspond-
       ing "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::Read-
       Line::*" 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 v5.8.8                       2001-09-21                 Term::ReadLine(3)