1Term::ReadLine(3pm) Perl Programmers Reference Guide Term::ReadLine(3pm)
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6 Term::ReadLine - Perl interface to various "readline" packages. If no
7 real package is found, substitutes stubs instead of basic functions.
8
10 use Term::ReadLine;
11 my $term = Term::ReadLine->new('Simple Perl calc');
12 my $prompt = "Enter your arithmetic expression: ";
13 my $OUT = $term->OUT || \*STDOUT;
14 while ( defined ($_ = $term->readline($prompt)) ) {
15 my $res = eval($_);
16 warn $@ if $@;
17 print $OUT $res, "\n" unless $@;
18 $term->addhistory($_) if /\S/;
19 }
20
22 This package is just a front end to some other packages. It's a stub to
23 set up a common interface to the various ReadLine implementations found
24 on CPAN (under the "Term::ReadLine::*" namespace).
25
27 All the supported functions should be called as methods, i.e., either
28 as
29 $term = Term::ReadLine->new('name');
31 or as
33 $term->addhistory('row');
35 where $term is a return value of Term::ReadLine->new().
37 "ReadLine" returns the actual package that executes the commands.
39 Among possible values are "Term::ReadLine::Gnu",
40 "Term::ReadLine::Perl", "Term::ReadLine::Stub".
41 "new" returns the handle for subsequent calls to following
43 functions. Argument is the name of the application.
44 Optionally can be followed by two arguments for "IN" and
45 "OUT" filehandles. These arguments should be globs.
46 "readline" gets an input line, possibly with actual "readline"
48 support. Trailing newline is removed. Returns "undef" on
49 "EOF".
50 "addhistory"
52 adds the line to the history of input, from where it can be
53 used if the actual "readline" is present.
54 "IN", "OUT" return the filehandles for input and output or "undef" if
56 "readline" input and output cannot be used for Perl.
57 "MinLine" If argument is specified, it is an advice on minimal size
59 of line to be included into history. "undef" means do not
60 include anything into history. Returns the old value.
61 "findConsole"
63 returns an array with two strings that give most
64 appropriate names for files for input and output using
65 conventions "<$in", ">out".
66 Attribs returns a reference to a hash which describes internal
68 configuration of the package. Names of keys in this hash
69 conform to standard conventions with the leading "rl_"
70 stripped.
71 "Features" Returns a reference to a hash with keys being features
73 present in current implementation. Several optional
74 features are used in the minimal interface: "appname"
75 should be present if the first argument to "new" is
76 recognized, and "minline" should be present if "MinLine"
77 method is not dummy. "autohistory" should be present if
78 lines are put into history automatically (maybe subject to
79 "MinLine"), and "addhistory" if "addhistory" method is not
80 dummy.
81 If "Features" method reports a feature "attribs" as
83 present, the method "Attribs" is not dummy.
84
86 Actually "Term::ReadLine" can use some other package, that will support
87 a richer set of commands.
88 All these commands are callable via method interface and have names
90 which conform to standard conventions with the leading "rl_" stripped.
91 The stub package included with the perl distribution allows some
93 additional methods:
94 "tkRunning" makes Tk event loop run when waiting for user input (i.e.,
96 during "readline" method).
97 "ornaments" makes the command line stand out by using termcap data.
99 The argument to "ornaments" should be 0, 1, or a string of
100 a form "aa,bb,cc,dd". Four components of this string
101 should be names of terminal capacities, first two will be
102 issued to make the prompt standout, last two to make the
103 input line standout.
104 "newTTY" takes two arguments which are input filehandle and output
106 filehandle. Switches to use these filehandles.
107 One can check whether the currently loaded ReadLine package supports
109 these methods by checking for corresponding "Features".
110
112 None
113
115 The environment variable "PERL_RL" governs which ReadLine clone is
116 loaded. If the value is false, a dummy interface is used. If the value
117 is true, it should be tail of the name of the package to use, such as
118 "Perl" or "Gnu".
119 As a special case, if the value of this variable is space-separated,
121 the tail might be used to disable the ornaments by setting the tail to
122 be "o=0" or "ornaments=0". The head should be as described above, say
123 If the variable is not set, or if the head of space-separated list is
125 empty, the best available package is loaded.
126 export "PERL_RL=Perl o=0" # Use Perl ReadLine without ornaments
128 export "PERL_RL= o=0" # Use best available ReadLine without ornaments
129 (Note that processing of "PERL_RL" for ornaments is in the discretion
131 of the particular used "Term::ReadLine::*" package).
132
134 It seems that using Term::ReadLine from Emacs minibuffer doesn't work
135 quite right and one will get an error message like
136 Cannot open /dev/tty for read at ...
138 One possible workaround for this is to explicitly open /dev/tty like
140 this
141 open (FH, "/dev/tty" )
143 or eval 'sub Term::ReadLine::findConsole { ("&STDIN", "&STDERR") }';
144 die $@ if $@;
145 close (FH);
146 or you can try using the 4-argument form of Term::ReadLine->new().
148perl v5.12.4 2011-06-07 Term::ReadLine(3pm)