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 The strings returned may not be useful for 3-argument
68 open().
69 Attribs returns a reference to a hash which describes internal
71 configuration of the package. Names of keys in this hash
72 conform to standard conventions with the leading "rl_"
73 stripped.
74 "Features" Returns a reference to a hash with keys being features
76 present in current implementation. Several optional
77 features are used in the minimal interface: "appname"
78 should be present if the first argument to "new" is
79 recognized, and "minline" should be present if "MinLine"
80 method is not dummy. "autohistory" should be present if
81 lines are put into history automatically (maybe subject to
82 "MinLine"), and "addhistory" if "addhistory" method is not
83 dummy.
84 If "Features" method reports a feature "attribs" as
86 present, the method "Attribs" is not dummy.
87
89 Actually "Term::ReadLine" can use some other package, that will support
90 a richer set of commands.
91 All these commands are callable via method interface and have names
93 which conform to standard conventions with the leading "rl_" stripped.
94 The stub package included with the perl distribution allows some
96 additional methods:
97 "tkRunning" makes Tk event loop run when waiting for user input (i.e.,
99 during "readline" method).
100 "event_loop"
102 Registers call-backs to wait for user input (i.e., during
103 "readline" method). This supersedes tkRunning.
104 The first call-back registered is the call back for
106 waiting. It is expected that the callback will call the
107 current event loop until there is something waiting to get
108 on the input filehandle. The parameter passed in is the
109 return value of the second call back.
110 The second call-back registered is the call back for
112 registration. The input filehandle (often STDIN, but not
113 necessarily) will be passed in.
114 For example, with AnyEvent:
116 $term->event_loop(sub {
118 my $data = shift;
119 $data->[1] = AE::cv();
120 $data->[1]->recv();
121 }, sub {
122 my $fh = shift;
123 my $data = [];
124 $data->[0] = AE::io($fh, 0, sub { $data->[1]->send() });
125 $data;
126 });
127 The second call-back is optional if the call back is
129 registered prior to the call to $term->readline.
130 Deregistration is done in this case by calling event_loop
132 with "undef" as its parameter:
133 $term->event_loop(undef);
135 This will cause the data array ref to be removed, allowing
137 normal garbage collection to clean it up. With AnyEvent,
138 that will cause $data->[0] to be cleaned up, and AnyEvent
139 will automatically cancel the watcher at that time. If
140 another loop requires more than that to clean up a file
141 watcher, that will be up to the caller to handle.
142 "ornaments" makes the command line stand out by using termcap data.
144 The argument to "ornaments" should be 0, 1, or a string of
145 a form "aa,bb,cc,dd". Four components of this string
146 should be names of terminal capacities, first two will be
147 issued to make the prompt standout, last two to make the
148 input line standout.
149 "newTTY" takes two arguments which are input filehandle and output
151 filehandle. Switches to use these filehandles.
152 One can check whether the currently loaded ReadLine package supports
154 these methods by checking for corresponding "Features".
155
157 None
158
160 The environment variable "PERL_RL" governs which ReadLine clone is
161 loaded. If the value is false, a dummy interface is used. If the value
162 is true, it should be tail of the name of the package to use, such as
163 "Perl" or "Gnu".
164 As a special case, if the value of this variable is space-separated,
166 the tail might be used to disable the ornaments by setting the tail to
167 be "o=0" or "ornaments=0". The head should be as described above, say
168 If the variable is not set, or if the head of space-separated list is
170 empty, the best available package is loaded.
171 export "PERL_RL=Perl o=0" # Use Perl ReadLine sans ornaments
173 export "PERL_RL= o=0" # Use best available ReadLine sans ornaments
174 (Note that processing of "PERL_RL" for ornaments is in the discretion
176 of the particular used "Term::ReadLine::*" package).
177perl v5.26.3 2019-05-11 Term::ReadLine(3pm)