MirOS Manual: Term::ReadLine(3p)


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

NAME

     Term::ReadLine - Perl interface to various "readline" pack-
     ages. 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().

     "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 fol-
                 lowing 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 "read-
                 line" support. Trailing newline is removed.
                 Returns "undef" on "EOF".

     "addhistory"
                 adds the line to the history of input, from

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                 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 his-
                 tory.  "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 conven-
                 tions 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 automati-
                 cally (maybe subject to "MinLine"), and "addhis-
                 tory" 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"

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                 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 orna-
     ments 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::*" pack-
     age).

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

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         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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