Switch to SpeakEasy.net DSL

The Modular Manual Browser

Home Page
Manual: (OpenBSD-3.6)
Apropos / Subsearch:
optional field

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

       Term::ReadLine - Perl interface to various "readline"
       packages.  If no real package is found, substitutes stubs
       instead of basic functions.

         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/;

       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


       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",

       "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".

                   adds the line to the history of input, from
                   where it can be used if the actual "readline"

perl v5.8.5                 2002-11-06                          1

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

                   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.

                   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 con-
                   ventions 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 min-
                   imal 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 automat-
                   ically (maybe subject to "MinLine"), and
                   "addhistory" if "addhistory" method is not

                   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 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

perl v5.8.5                 2002-11-06                          2

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

                   "aa,bb,cc,dd".  Four components of this string
                   should be names of terminal capacities, first
                   two will be issued to make the prompt stand-
                   out, last two to make the input line standout.

       "newTTY"    takes two arguments which are input filehandle
                   and output filehandle.  Switches to use these

       One can check whether the currently loaded ReadLine pack-
       age supports these methods by checking for corresponding


       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 "orna-
       ments=0".  The head should be as described above, say

       If the variable is not set, or if the head of space-sepa-
       rated 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::*"

       It seems that using Term::ReadLine from Emacs minibuffer
       doesn't work quite right and one will get an error message

           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::Read-

perl v5.8.5                 2002-11-06                          3