Index for Section 3

Alphabetical listing for T

Bottom of page

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 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 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.

  "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 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().

Index for Section 3

Alphabetical listing for T

Top of page