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 = new Term::ReadLine '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 = new Term::ReadLine 'name';
31 or as
33 $term->addhistory('row');
35 where $term is a return value of Term::ReadLine->new().
37 "ReadLine" returns the actual package that executes the commands.
39 Among possible values are "Term::ReadLine::Gnu",
40 "Term::ReadLine::Perl", "Term::ReadLine::Stub".
41 "new" returns the handle for subsequent calls to following func‐
43 tions. Argument is the name of the application. Optionally
44 can be followed by two arguments for "IN" and "OUT" file‐
45 handles. These arguments should be globs.
46 "readline" gets an input line, possibly with actual "readline" sup‐
48 port. Trailing newline is removed. Returns "undef" on
49 "EOF".
50 "addhistory"
52 adds the line to the history of input, from where it can be
53 used if the actual "readline" is present.
54 "IN", "OUT" return the filehandles for input and output or "undef" if
56 "readline" input and output cannot be used for Perl.
57 "MinLine" If argument is specified, it is an advice on minimal size
59 of line to be included into history. "undef" means do not
60 include anything into history. Returns the old value.
61 "findConsole"
63 returns an array with two strings that give most appropri‐
64 ate names for files for input and output using conventions
65 "<$in", ">out".
66 Attribs returns a reference to a hash which describes internal con‐
68 figuration of the package. Names of keys in this hash con‐
69 form 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 fea‐
74 tures are used in the minimal interface: "appname" should
75 be present if the first argument to "new" is recognized,
76 and "minline" should be present if "MinLine" method is not
77 dummy. "autohistory" should be present if lines are put
78 into history automatically (maybe subject to "MinLine"),
79 and "addhistory" if "addhistory" method is not dummy.
80 If "Features" method reports a feature "attribs" as
82 present, the method "Attribs" is not dummy.
83
85 Actually "Term::ReadLine" can use some other package, that will support
86 a richer set of commands.
87 All these commands are callable via method interface and have names
89 which conform to standard conventions with the leading "rl_" stripped.
90 The stub package included with the perl distribution allows some addi‐
92 tional methods:
93 "tkRunning" makes Tk event loop run when waiting for user input (i.e.,
95 during "readline" method).
96 "ornaments" makes the command line stand out by using termcap data.
98 The argument to "ornaments" should be 0, 1, or a string of
99 a form "aa,bb,cc,dd". Four components of this string
100 should be names of terminal capacities, first two will be
101 issued to make the prompt standout, last two to make the
102 input line standout.
103 "newTTY" takes two arguments which are input filehandle and output
105 filehandle. Switches to use these filehandles.
106 One can check whether the currently loaded ReadLine package supports
108 these methods by checking for corresponding "Features".
109
111 None
112
114 The environment variable "PERL_RL" governs which ReadLine clone is
115 loaded. If the value is false, a dummy interface is used. If the value
116 is true, it should be tail of the name of the package to use, such as
117 "Perl" or "Gnu".
118 As a special case, if the value of this variable is space-separated,
120 the tail might be used to disable the ornaments by setting the tail to
121 be "o=0" or "ornaments=0". The head should be as described above, say
122 If the variable is not set, or if the head of space-separated list is
124 empty, the best available package is loaded.
125 export "PERL_RL=Perl o=0" # Use Perl ReadLine without ornaments
127 export "PERL_RL= o=0" # Use best available ReadLine without ornaments
128 (Note that processing of "PERL_RL" for ornaments is in the discretion
130 of the particular used "Term::ReadLine::*" package).
131
133 It seems that using Term::ReadLine from Emacs minibuffer doesn't work
134 quite right and one will get an error message like
135 Cannot open /dev/tty for read at ...
137 One possible workaround for this is to explicitly open /dev/tty like
139 this
140 open (FH, "/dev/tty" )
142 or eval 'sub Term::ReadLine::findConsole { ("&STDIN", "&STDERR") }';
143 die $@ if $@;
144 close (FH);
145 or you can try using the 4-argument form of Term::ReadLine->new().
147perl v5.8.8 2001-09-21 Term::ReadLine(3pm)