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Term::ReadLine

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. At the moment
       this description is written, the only such package is Term-ReadLine,
       available on CPAN near you. The real target of this stub package is to
       set up a common interface to whatever Readline emerges with time.

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 following func-
                   tions. Argument is the name of the application. Optionally
                   can be followed by two arguments for "IN" and "OUT" file-
                   handles. These arguments should be globs.

       "readline"  gets an input line, possibly with actual "readline" sup-
                   port. 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 appropri-
                   ate names for files for input and output using conventions
                   "<$in", ">out".

       Attribs     returns a reference to a hash which describes internal con-
                   figuration of the package. Names of keys in this hash con-
                   form 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 fea-
                   tures 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
       reacher 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 addi-
       tional 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".

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().



perl v5.8.6                       2001-09-21                 Term::ReadLine(3)