IO::Prompter - Prompt for input, read it, clean it, return it.
This document describes IO::Prompter version 0.004015
use IO::Prompter;
while (prompt -num, 'Enter a number') {
say "You entered: $_";
}
my $passwd
= prompt 'Enter your password', -echo=>'*';
my $selection
= prompt 'Choose wisely...', -menu => {
wealth => [ 'moderate', 'vast', 'incalculable' ],
health => [ 'hale', 'hearty', 'rude' ],
wisdom => [ 'cosmic', 'folk' ],
}, '>';
-
Several features of this module are known to have problems under
Windows. If using that platform, you may have more success
(and less distress) by trying IO::Prompt::Tiny, IO::Prompt::Simple,
or IO::Prompt::Hooked first.
-
By default the
prompt() subroutine does not return a string; it
returns an object with overloaded string and boolean conversions.
This object always evaluates true in boolean contexts, unless the
read operation actually failed. This means that the object evaluates
true even when the input value is zero or
an empty string. See Returning raw data to turn off this
(occasionally counter-intuitive) behaviour.
IO::Prompter exports a single subroutine, prompt, that prints a
prompt (but only if the program's selected input and output streams are
connected to a terminal), then reads some input, then chomps it, and
finally returns an object representing that text.
The prompt() subroutine expects zero-or-more arguments.
Any argument that starts with a hyphen (-) is treated as a named
option (many of which require an associated value, that may be passed as
the next argument). See Summary of options and Options reference for details of the available options.
Any other argument that is a string is treated as (part of) the prompt
to be displayed. All such arguments are concatenated together before the
prompt is issued. If no prompt string is provided, the string
'> ' is used instead.
Normally, when prompt() is called in either list or scalar context,
it returns an opaque object that autoconverts to a string. In scalar
boolean contexts this return object evaluates true if the input
operation succeeded. In list contexts, if the input operation fails
prompt() returns an empty list instead of a return object. This
allows failures in list context to behave correctly (i.e. be false).
If you particularly need a list-context call to prompt() to always
return a value (i.e. even on failure), prefix the call with scalar:
# Only produces as many elements
# as there were successful inputs...
my @data = (
prompt(' Name:'),
prompt(' Age:'),
prompt('Score:'),
);
# Always produces exactly three elements
# (some of which may be failure objects)...
my @data = (
scalar prompt(' Name:'),
scalar prompt(' Age:'),
scalar prompt('Score:'),
);
In void contexts, prompt() still requests input, but also issues a
warning about the general uselessness of performing an I/O operation
whose results are then immediately thrown away.
See Useful useless uses of prompt() for an exception to this.
The prompt() function also sets $_ if it is called in a boolean
context but its return value is not assigned to a variable. Hence, it is
designed to be a drop-in replacement for readline or <>.
All the options for prompt() start with a hyphen (-).
Most have both a short and long form. The short form is always
the first letter of the long form.
Most options have some associated value. For short-form options, this
value is specified as a string appended to the option itself. The
associated value for long-form options is always specified as a
separated argument, immediately following the option (typically
separated from it by a =>).
Note that this implies that short-form options may not be able to
specify every possible associated value (for example, the short-form
-d option cannot specify defaults with values 'efault' or
'$%^!'). In such cases, just use the long form of the option
(for example: -def => 'efault' > or -default=>'$%^!').
Note: For options preceded by an asterisk, the short form is actually
a Perl file operator, and hence cannot be used by itself.
Either use the long form of these options,
or bundle them with another option,
or add a ``no-op'' to them.
Short Long
form form Effect
===== ============= ======================================
-a -argv Prompt for @ARGV data if !@ARGV
-comp[lete]=>SPEC Complete input on <TAB>, as specified
-dSTR -def[ault]=>STR What to return if only <ENTER> typed
-DEF[AULT]=>STR (as above, but skip any -must checking)
* -e[STR] -echo=>STR Echo string for each character typed
-echostyle=>SPEC What colour/style to echo input in
* -f -filenames Input should be name of a readable file
-fail=>VALUE Return failure if input smartmatches value
-guar[antee]=>SPEC Only allow the specified words to be entered
-h[STR] -hist[ory][=>SPEC] Specify the history set this call belongs to
-in=>HANDLE Read from specified handle
-i -integer[=>SPEC] Accept only valid integers (that smartmatch SPEC)
-k -keyletters Accept only keyletters (as specified in prompt)
* -l -line Don't autochomp
-menu=>SPEC Specify a menu of responses to be displayed
-must=>HASHREF Specify requirements/constraints on input
-n -num[ber][=>SPEC] Accept only valid numbers (that smartmatch SPEC)
-out=>HANDLE Prompt to specified handle
-prompt=>STR Specify prompt explicitly
* -rSTR -ret[urn]=>STR After input, echo this string instead of <CR>
* -s -1 -sing[le] Return immediately after first key pressed
-stdio Use STDIN and STDOUT for prompting
-style=>SPEC What colour/style to display the prompt text in
-tNUM -time[out]=>NUM Specify a timeout on the input operation
-v -verb[atim] Return the input string (no context sensitivity)
-void Don't complain in void context
* -w -wipe Clear screen
-wipefirst Clear screen on first prompt() call only
* -y -yes [=> NUM] Return true if [yY] entered, false otherwise
-yn -yesno [=> NUM] Return true if [yY] entered, false if [nN]
-Y -Yes [=> NUM] Return true if Y entered, false otherwise
-YN -YesNo [=> NUM] Return true if Y entered, false if N
* -_ No-op (handy for bundling ambiguous short forms)
Any of the options listed above (and described in detail below) can be
automatically applied to every call to prompt() in the current
lexical scope, by passing them (via an array reference) as the arguments
to a use IO::Prompter statement.
For example:
use IO::Prompter;
# This call has no automatically added options...
my $assent = prompt "Do you wish to take the test?", -yn;
{
use IO::Prompter [-yesno, -single, -style=>'bold'];
# These three calls all have: -yesno, -single, -style=>'bold' options
my $ready = prompt 'Are you ready to begin?';
my $prev = prompt 'Have you taken this test before?';
my $hints = prompt 'Do you want hints as we go?';
}
# This call has no automatically added options...
scalar prompt 'Type any key to start...', -single;
The current scope's lexical options are always prepended to the
argument list of any call to prompt() in that scope.
To turn off any existing automatic options for the rest of the current
scope, use:
use IO::Prompter [];
You can also ask IO::Prompter to export modified versions of prompt()
with zero or more options prebound. For example, you can request an
ask() subroutine that acts exactly like prompt() but has the -
yn option pre-specified, or a pause() subroutine that is prompt()
with a ``canned'' prompt and the -echo, -single, and -void options.
To specify such subroutines, pass a single hash reference when
loading the module:
use IO::Prompter {
ask => [-yn],
pause => [-prompt=>'(Press any key to continue)', -echo, -single, -void],
}
Each key will be used as the name of a separate subroutine to be
exported, and each value must be an array reference, containing the
arguments that are to be automatically supplied.
The resulting subroutines are simply lexically scoped wrappers around
prompt(), with the specified arguments prepended to the normal
argument list, equivalent to something like:
my sub ask {
return prompt(-yn, @_);
}
my sub pause {
return prompt(-prompt=>'(Press any key to continue)', -echo, -single, -void, @_);
}
Note that these subroutines are lexically scoped, so if you want to use
them throughtout a source file, they should be declared in the outermost
scope of your program.
-prompt => STRING
-pSTRING
By default, any argument passed to prompt() that does not begin with
a hyphen is taken to be part of the prompt string to be displayed before
the input operation. Moreover, if no such string is specified in the
argument list, the function supplies a default prompt ('> ')
automatically.
The -prompt option allows you to specify a prompt explicitly, thereby
enabling you to use a prompt that starts with a hyphen:
my $input
= prompt -prompt=>'-echo';
or to disable prompting entirely:
my $input
= prompt -prompt => "";
Note that the use of the -prompt option doesn't override other string
arguments, it merely adds its argument to the collective prompt.
If the specified prompt ends in a non-whitespace character, prompt()
adds a single space after it, to better format the output. On the other
hand, if the prompt ends in a newline, prompt() removes that
character, to keep the input position on the same line as the prompt.
You can use that second feature to override the first, if necessary. For
example, if you wanted your prompt to look like:
Load /usr/share/dict/_
(where the _ represents the input cursor), then a call like:
$filename = prompt 'Load /usr/share/dict/';
would not work because it would automatically add a space, producing:
Load /usr/share/dict/ _
But since a terminal newline is removed, you could achieve the desired effect
with:
$filename = prompt "Load /usr/share/dict/\n";
If for some reason you do want a newline at the end of the prompt (i.e.
with the input starting on the next line) just put two newlines at the end
of the prompt. Only the very last one will be removed.
-style => SPECIFICATION
If the Term::ANSIColor module is available, this option can be used
to specify the colour and styling (e.g. bold, inverse, underlined, etc.)
in which the prompt is displayed.
You can can specify that styling as a single string:
prompt 'next:' -style=>'bold red on yellow';
or an array of styles:
prompt 'next:' -style=>['bold', 'red', 'on_yellow'];
The range of styles and colour names that the option understands is
quite extensive. All of the following work as expected:
prompt 'next:' -style=>'bold red on yellow';
prompt 'next:' -style=>'strong crimson on gold';
prompt 'next:' -style=>'highlighted vermilion, background of cadmium';
prompt 'next:' -style=>'vivid russet over amber';
prompt 'next:' -style=>'gules fort on a field or';
However, because Term::ANSIColor maps everything back to the
standard eight ANSI text colours and seven ANSI text styles, all of the
above will also be rendered identically. See that module's
documentation for details.
If Term::ANSIColor is not available, this option is silently ignored.
Please bear in mind that up to 10% of people using your interface will
have some form of colour vision impairment, so its always a good idea
to differentiate information by style and colour, rather than by colour
alone. For example:
if ($dangerous_action) {
prompt 'Really proceed?', -style=>'bold red underlined';
}
else {
prompt 'Proceed?', -style=>'green';
}
Also bear in mind that (even though -style does support the 'blink'
style) up to 99% of people using your interface will have Flashing Text
Tolerance Deficiency. Just say ``no''.
-out => FILEHANDLE
-in => FILEHANDLE
-stdio
The -out option (which has no short form) is used to specify
where the prompt should be written to. If this option is not specified,
prompts are written to the currently select-ed filehandle. The most
common usage is:
prompt(out => *STDERR)
The -in option (which also has no short form) specifies where the input
should be read from. If this option is not specified, input is read from
the *ARGV filehandle. The most common usage is:
prompt(in => *STDIN)
in those cases where *ARGV has been opened to a file, but you still
wish to interact with the terminal (assuming *STDIN is opened to that
terminal).
The -stdio option (which again has no short form) is simply a shorthand
for: -in => *STDIN, -out => *STDOUT. This is particularly useful when
there are arguments on the commandline, but you don't want prompt to treat
those arguments as filenames for magic *ARGV reads.
-timeout => N
-tN
Normally, the prompt() function simply waits for input. However,
you can use this option to specify a timeout on the read operation.
If no input is received within the specified N seconds, the call
to prompt() either returns the value specified by
the -default option
(if any), or else an object indicating the read failed.
Note that, if the short form is used, N must be an integer. If the long
form is used, N may be an integer or floating point value.
You can determine whether an input operation timed out, even if a
default value was returned, by calling the timedout() method on the
object returned by prompt():
if (prompt('Continue?', -y1, -timeout=>60) && !$_->timedout) {
...
}
If a time-out occurred, the return value of timedout() is a string
describing the timeout, such as:
"timed out after 60 seconds"
- -menu => SPECIFICATION
-
You can limit the allowable responses to a prompt, by providing a menu.
A menu is specified using the -menu option, and the menu choices
are specified as an argument to the option, either as a reference to
an array, hash, or string, or else as a literal string.
If the menu is specified in a hash, prompt() displays the keys of the
hash, sorted alphabetically, and with each alternative marked with a
single alphabetic character (its ``selector key'').
For example, given:
prompt 'Choose...',
-menu=>{ 'live free'=>1, 'die'=>0, 'transcend'=>-1 },
'>';
prompt() will display:
Choose...
a. die
b. live free
c. transcend
> _
It will then only permit the user to enter a valid selector key (in the
previous example: 'a', 'b', or 'c'). Once one of the alternatives is
selected, prompt() will return the corresponding value from the hash
(0, 1, or -1, respectively, in this case).
Note that the use of alphabetics as selector keys inherently limits the
number of usable menu items to 52. See Numeric menus for a way to
overcome this limitation.
A menu is treated like a special kind of prompt, so that any
other prompt strings in the prompt() call will appear either before or
after the menu of choices, depending on whether they appear before or
after the menu specification in the call to prompt().
If an array is used to specify the choices:
prompt 'Choose...',
-menu=>[ 'live free', 'die', 'transcend' ],
'>';
then each array element is displayed (in the original array order) with
a selector key:
Choose...
a. live free
b. die
c. transcend
> _
and prompt() returns the element corresponding to the selection (i.e.
it returns 'live free' if 'a' is entered, 'die' if 'b' is entered, or
'transcend' if 'c' is entered).
Hence, the difference between using an array and a hash is that the
array allows you to control the order of items in the menu, whereas a
hash allows you to show one thing (i.e. keys) but have something related
(i.e. values) returned instead.
If the argument after -menu is a string or a reference to a string, the
option splits the string on newlines, and treats the resulting list as if it
were an array of choices. This is useful, for example, to request the user
select a filename:
my $files = `ls`;
prompt 'Select a file...', -menu=>$files, '>';
As the previous examples indicate, each menu item is given a unique
alphabetic selector key. However, if the -number or -integer
option is specified as well:
prompt 'Choose...',
-number,
-menu=>{ 'live free'=>1, 'die'=>0, 'transcend'=>-1 },
'>';
prompt() will number each menu item instead, using consecutive integers
as the selector keys:
Choose...
1. die
2. live free
3. transcend
> _
This allows for an unlimited number of alternatives in a single menu,
but prevents the use of -single for one-key selection from menus if
the menu has more than nine items.
If you use a hash to specify a menu, the values of the hash do not have
to be strings. Instead, they can be references to nested hashes or
arrays.
This allows you to create hierarchical menus, where a selection at the
top level may lead to a secondary menu, etc. until an actual choice is
possible. For example, the following call to prompt:
my $choices = {
animates => {
animals => {
felines => [qw<cat lion lynx>],
canines => [qw<dog fox wolf>],
bovines => [qw<cow ox buffalo>],
},
fish => [qw<shark carp trout bream>],
},
inanimates => {
rocks => [qw<igneous metamorphic sedimentary>],
languages => [qw<Perl Python Ruby Tcl>],
},
};
my $result = prompt -1, 'Select a species...', -menu=>$choices, '> ';
might result in an interaction like this:
Select a species...
a. animates
b. inanimates
> a
Select from animates:
a. animals
b. fish
> b
Select from fish:
a. shark
b. carp
c. trout
d. bream
> c
At which point, prompt() would return the string 'trout'.
Note that you can nest an arbitrary number of hashes, but that each
``bottom'' level choice has to be either a single string, or an array
of strings.
Within a hierarchical menu, the user must either select a valid option
(by entering the corresponding letter), or else may request that they be
taken back up a level in the hierarchy, by entering <ESC>.
Pressing <ESC> at the top level of a menu causes the call to
prompt() to immediately return with failure.
-argv
-a
The prompt() subroutine can be used to request that the user provide
command-line arguments interactively. When requested, the input
operation is only carried out if @ARGV is empty.
Whatever the user enters is broken into a list and assigned to @ARGV.
The input is first globbed for file expansions, and has any
environment variables (of the form $VARNAME interpolated). The
resulting string is then broken into individual words, except where
parts of it contain single or double quotes, the contents of which are
always treated as a single string.
This feature is most useful during development, to allow a program to be
run from within an editor, and yet pass it a variety of command-lines. The
typical usage is (at the start of a program):
use IO::Prompter;
BEGIN { prompt -argv }
However, because this pattern is so typical, there is a shortcut:
use IO::Prompter -argv;
You can also specify the name with which the program args, are to
be prompted, in the usual way (i.e. by providing a prompt):
use IO::Prompter -argv, 'demo.pl';
Note, however, the critical difference between that shortcut
(which calls prompt -argv when the module is loaded) and:
use IO::Prompter [-argv];
(which sets -argv as an automatic option for every subsequent call to
prompt() in the current lexical scope).
Note too that the -argv option also implies -complete='filenames'>.
-comp[lete] => SPECIFICATION
When this option is specified, the prompt() subroutine will complete
input using the specified collection of strings. By default, when
completion is active, word completion is requested using the <TAB>
key, but this can be changed by setting the $IO_PROMPTER_COMPLETE_KEY
environment variable. Once completion has been initiated, you can use
the completion key or else <CTRL-N> to advance to the next completion
candidate. You can also use <CTRL-P> to back up to the previous
candidate.
The specific completion mechanism can be defined either using a
subroutine, an array reference, a hash reference, or a special string:
Specification Possible completions supplied by...
sub {...} ...whatever non-subroutine specification
(as listed below) is returned when the
subroutine is called. The subroutine is passed
the words of the current input text, split on
whitespace, as its argument list.
[...] ...the elements of the array
{...} ...the keys of the hash
'filenames' ...the list of files supplied by globbing the
last whitespace-separated word of the input text
'dirnames' ...the list of directories supplied by globbing the
last whitespace-separated word of the input text
If an array or hash is used, only those elements or keys that begin with
the last whitespace-separated word of the current input are offered as
completions.
For example:
# Complete with the possible commands...
my $next_cmd
= prompt -complete => \%cmds;
# Complete with valid usernames...
my $user
= prompt -complete => \@usernames;
# Complete with valid directory names...
my $file
= prompt -complete => 'dirnames';
# Complete with cmds on the first word, and filenames on the rest...
my $cmdline
= prompt -complete => sub { @_ <= 1 ? \%cmds : 'filenames' };
The prompt() subroutine also tracks previous input and allows you to
complete with that instead. No special option is required, as the
feature is enabled by default.
At the start of a prompted input, the user can cycle backwards through
previous inputs by pressing <CTRL-R> (this can be changed
externally by setting the $IO_PROMPTER_HISTORY_KEY environment
variable, or internally by assigning a new keyname to
$ENV{IO_PROMPTER_HISTORY_KEY}). After the first <CTRL-R>,
subsequent <CTRL-R>'s will recall earlier inputs. You can also
use <CTRL-N> and <CTRL-P>
(as in user-specified completions) to move
back and forth through your input history.
If the user has already typed some input, the completion mechanism
will only show previous inputs that begin with that partial input.
- -h[NAME]
-
- -hist[ory] [=> NAME]
-
By default, IO::Prompter tracks every call to prompt() within a
program, and accumulates a single set of history completions for all of
them. That means that, at any prompt, <CTRL-R> will take the user
back through every previous input, regardless of which call to
prompt() originally retrieved it.
Sometimes that's useful, but sometimes you might prefer that different
calls to prompt() retained distinct memories. For example, consider
the following input loop:
while (my $name = prompt 'Name:') {
my $grade = prompt 'Grade:', -integer;
my $comment = prompt 'Comment:';
...
}
If you're entering a name, there's no point in prompt() offering
to complete it with previous grades or comments. In fact, that's
just annoying.
IO::Prompter allows you to specify that a particular call to
prompt() belongs to a particular ``history set''. Then it completes
input history using only the history of those calls belonging to the
same history set.
So the previous example could be improved like so:
while (my $name = prompt 'Name:', -hNAME) {
my $grade = prompt 'Grade:', -hGRADE, -integer;
my $comment = prompt 'Comment:', -hOTHER;
...
}
Now, when prompting for a name, only those inputs in the 'NAME'
history set will be offered as history completions. Likewise only
previous grades will be recalled when prompting for grades and earlier
only comments when requesting comments.
If you specify the -h or -history option without providing the
name of the required history set, prompt() uses the prompt text
itself as the name of the call's history set. So the previous example
would work equally well if written:
while (my $name = prompt 'Name:', -h) {
my $grade = prompt 'Grade:', -h, -integer;
my $comment = prompt 'Comment:', -h;
...
}
though now the names of the respective history sets would now be
'Name: ', 'Grade: ', and 'Comment: '. This is by far the more
common method of specifying history sets, with explicitly named sets
generally only being used when two or more separate calls to
prompt() have to share a common history despite using distinct
prompts. For example:
for my $n (1..3) {
$address .= prompt "Address (line $n):", -hADDR;
}
If you specify 'NONE' as the history set, the input is not
recorded in the history. This is useful when inputting passwords.
By default, when user-defined autocompletion is requested, the
prompt() subroutine determines the list of possible completions,
displays it above the prompt, and completes to the longest common
prefix. If the completion key is pressed again immediately, the
subroutine then proceeds to complete with each possible completion in a
cyclic sequence. This is known as ``list+longest full'' mode.
On the other hand, when historical completion is requested, prompt()
just immediately cycles through previous full inputs. This is known as ``full''
mode.
You can change these behaviours by setting the
$IO_PROMPTER_COMPLETE_MODES and $IO_PROMPTER_HISTORY_MODES
environment variables before the module is loaded (either in your shell,
or in a BEGIN block before the module is imported).
Specifically, you can set the individual string values of either of
these variables to a whitespace-separated sequence containing any of the
following:
list List all options above the input line
longest Complete to the longest common prefix
full Complete with each full match in turn
For example:
# Just list options without actually completing...
BEGIN{ $ENV{IO_PROMPTER_COMPLETE_MODES} = 'list'; }
# Just cycle full alternatives on each <TAB>...
BEGIN{ $ENV{IO_PROMPTER_COMPLETE_MODES} = 'full'; }
# For history completion, always start with the
# longest common prefix on the first <CTRL-R>,
# then just list the alternatives on a subsequent press...
BEGIN{ $ENV{IO_PROMPTER_HISTORY_MODES} = 'longest list'; }
-DEF[AULT] => STRING
-def[ault] => STRING
-dSTRING
If a default value is specified, that value will be returned if the user
enters an empty string at the prompt (i.e. if they just hit
<ENTER>/<RETURN> immediately) or if the input operation times out under
the timeout option.
Note that the default value is not added to the prompt, unless you
do so yourself. A typical usage might therefore be:
my $frequency
= prompt "Enter polling frequency [default: $DEF_FREQ]",
-num, -def=>$DEF_FREQ;
You can determine if the default value was autoselected (as opposed to
the same value being typed in explicitly) by calling the defaulted()
method on the object returned by prompt(), like so:
if ($frequency->defaulted) {
say "Using default frequency";
}
If you use the -must option
any default value must also satisfy all the constraints you specify,
unless you use the -DEFAULT form, which skips constraint checking
when the default value is selected.
If you use the -menu option,
the specified default value will be returned immediately <ENTER>/<RETURN> is
pressed, regardless of the depth you are within the menu. Note that the
default value specifies the value to be returned, not the selector key
to be entered. The default value does not even have to be one of the
menu choices.
-echo => STR
-eSTR
When this option is specified, the prompt() subroutine will echo the
specified string once for each character that is entered. Typically this
would be used to shroud a password entry, like so:
# Enter password silently:
my $passwd
= prompt 'Password:', -echo=>"";
# Echo password showing only asterisks:
my $passwd
= prompt 'Password:', -echo=>"*";
As a special case, if the -echo value contains a slash (/) and the
any of the <-yesno> options is also specified, the substring before the
slash is taken as the string to echo for a 'yes' input, and the
substring after the slash is echoed for a 'no' input.
Note that this option is only available when the Term::ReadKey module
is installed. If it is used when that module is not available, a warning
will be issued.
-echostyle => SPECIFICATION
The -echostyle option works for the text the user types in
the same way that the -style option works for the prompt.
That is, you can specify the style and colour in which the user's
input will be rendered like so:
# Echo password showing only black asterisks on a red background:
my $passwd
= prompt 'Password:', -echo=>"*", -echostyle=>'black on red';
Note that -echostyle is completely independent of -echo:
# Echo user's name input in bold white:
my $passwd
= prompt 'Name:', -echostyle=>'bold white';
The -echostyle option requires Term::ANSIColor, and will
be silently ignored if that module is not available.
When the Term::ReadKey module is available, prompt() also honours a
subset of the usual input cursor motion commands:
- CTRL-B
-
Move the cursor back one character
- CTRL-F
-
Move the cursor forward one character
- CTRL-A
-
Move the cursor to the start of the input
- CTRL-E
-
Move the cursor to the end of the input
-fail => VALUE
-fSTRING
If this option is specified, the final input value is compared with the
associated string or value, by smartmatching just before the call to
prompt() returns. If the two match, prompt() returns a failure
value. This means that instead of writing:
while (my $cmd = prompt '>') {
last if $cmd eq 'quit';
...
}
you can just write:
while (my $cmd = prompt '>', -fail=>'quit') {
...
}
- -guar[antee] => SPEC
-
This option allows you to control what input users can provide.
The specification can be a regex or a reference to an array or a hash.
If the specification is a regex, that regex is matched against the input
so far, every time an extra character is input. If the regex ever fails
to match, the guarantee fails.
If the specification is an array, the input so far is matched against
the same number of characters from the start of each of the (string)
elements of the array. If none of these substrings match the input, the
guarantee fails.
If the specification is a hash, the input so far is matched against the
same number of characters from the start of each key of the hash. If
none of these substrings match the input, the guarantee fails.
If the guarantee fails, the input is rejected
(just as the -must option
does). However, unlike -must, -guarantee rejects the input
character-by-character as it typed, and before it is even echoed. For
example, if your call to prompt() is:
my $animal = prompt -guarantee=>['cat','dog','cow'];
then at the prompt:
> _
you will only be able to type in 'c' or 'd'. If you typed 'c', then you would
only be able to type 'a' or 'o'. If you then typed 'o', you would only be able
to type 'w'.
In other words, -guarantee ensures that you can only type in a valid input,
and simply ignores any typing that would not lead to such an input.
To help users get the input right, specifying -guarantee as an array
or hash reference also automatically specifies a
-complete option with the array or hash
as its completion list as well. So, whenever a -guarantee is in
effect, the user can usually autocomplete the acceptable inputs.
Note, however, that -guarantee can only reject (or autocomplete)
input as it is typed if the Term::ReadKey module is available. If that
module cannot be loaded, -guarantee only applies its test after the
<ENTER>/<RETURN> key is pressed, and there will be no autocompletion
available.
- -i
-
- -integer [=> SPEC]
-
- -n
-
- -num[ber] [=> SPEC]
-
If any of these options are specified, prompt() will only accept a valid
integer or number as input, and will reprompt until one is entered.
If you need to restrict the kind of number further (say, to positive
integers), you can supply an extra constraint as an argument to the
long-form option. Any number entered must satisfy this constraint by
successfully smart-matching it. For example:
$rep_count = prompt 'How many reps?', -integer => sub{ $_ > 0 };
$die_roll = prompt 'What did you roll?', -integer => [1..6];
$factor = prompt 'Prime factor:', -integer => \&is_prime;
$score = prompt 'Enter score:', -number => sub{ 0 <= $_ && $_ <= 100 };
If the constraint is specified as a subroutine, the entered number will be
passed to it both as its single argument and in $_.
You cannot pass a scalar value directly as a constraint, except those strings
listed below. If you want a scalar value as a constraint, use a regex or
array reference instead:
# Wrong...
$answer = prompt "What's the ultimate answer?",
-integer => 42;
# Use this instead...
$answer = prompt "What's the ultimate answer?",
-integer => qr/^42$/;
# Or this...
$answer = prompt "What's the ultimate answer?",
-integer => [42];
Only the following strings may be passed directly as scalar value
constraints. They do mot match exactly, but instead act as specifiers
for one or more built-in constraints. You can also pass a string that
contains two or more of them, separated by whitespace, in which case
they must all be satisfied. The specifiers are:
- 'pos' or 'positive'
-
The number must be greater than zero
- 'neg' or 'negative'
-
The number must be less than zero
- 'zero'
-
The number must be equal to zero
- 'even' or 'odd'
-
The number must have the correct parity
You can also prepend "non" to any of the above to reverse their meaning.
For example:
$rep_count = prompt 'How much do you bid?', -number => 'positive';
$step_value = prompt 'Next step:', -integer => 'even nonzero';
- -f
-
- -filenames
-
You can tell prompt() to accept only valid filenames, using the
-filenames option (or its shortcut: -f).
This option is equivalent to the options:
-must => {
'File must exist' => sub { -e },
'File must be readable' => sub { -r },
},
-complete => 'filenames',
In other words -filenames requires prompt() to accept only the name
of an existing, readable file, and it also activates filename completion.
- -k
-
- -key[let[ter]][s]
-
A common interaction is to offer the user a range of actions, each of
which is specified by keying a unique letter, like so:
INPUT:
given (prompt '[S]ave, (R)evert, or (D)iscard:', -default=>'S') {
when (/R/i) { revert_file() }
when (/D/i) { discard_file() }
when (/S/i) { save_file() }
default { goto INPUT; }
}
This can be cleaned up (very slightly) by using a guarantee:
given (prompt '[S]ave, (R)evert, or (D)iscard:', -default=>'S',
-guarantee=>qr/[SRD]/i
) {
when (/R/i) { revert_file() }
when (/D/i) { discard_file() }
default { save_file() }
}
However, it's still annoying to have to specify the three key letters
twice (and the default choice three times) within the call to
prompt(). So IO::Prompter provides an option that extracts this
information directly from the prompt itself:
given (prompt '[S]ave, (R)evert, or (D)iscard:', -keyletters) {
when (/R/i) { revert_file() }
when (/D/i) { discard_file() }
default { save_file() }
}
This option scans the prompt string and extracts any purely alphanumeric
character sequences that are enclosed in balanced brackets of any kind
(square, angle, round, or curly). It then makes each of these character
sequences a valid input (by implicitly setting the -guarantee
option), and adds the first option in square brackets (if any) as the
-default value of the prompt.
Note that the key letters don't have to be at the start of a word, don't
have to be a single character, and can be either upper or lower case.
For example:
my $action = prompt -k, '(S)ave, Save(a)ll, (Ex)it without saving';
Multi-character key letters are often a good choice for options with
serious or irreversible consequences.
A common idiom with key letters is to use the -single option as well,
so that pressing any key letter immediately completes the input, without
the user having to also press <ENTER>/<RETURN>:
given (prompt -k1, '[S]ave, (R)evert, or (D)iscard:') {
when (/R/i) { revert_file() }
when (/D/i) { discard_file() }
default { save_file() }
}
- -l
-
- -line
-
The (encapsulated) string returned by prompt() is automatically chomped by
default. To prevent that chomping, specify this option.
- -must => HASHREF
-
This option allows you to specify requirements and constraints on the input
string that is returned by prompt(). These limitations are specified as the
values of a hash.
If the -must option is specified, once input is complete every value in the
specified hash is smartmatched against the input text. If any of them fail to
match, the input is discarded, the corresponding hash key is printed as an
error message, and the prompt is repeated.
Note that the values of the constraint hash cannot be single strings or
numbers, except for certain strings (such as 'pos', 'nonzero', or
'even', as described in Constraining input to numbers).
If you want to constrain the input to a single string or number (a very
unusual requirement), just place the value in an array, or match it
with a regex:
# This doesn't work...
my $magic_word = prompt "What's the magic word?",
-must => { 'be polite' => 'please' };
# Use this instead...
my $magic_word = prompt "What's the magic word?",
-must => { 'be polite' => ['please'] };
# Or, better still...
my $magic_word = prompt "What's the magic word?",
-must => { 'be polite' => qr/please/i };
The -must option allows you to test inputs against multiple
conditions and have the appropriate error messages for each displayed.
It also ensures that, when prompt() eventually returns, you are
guaranteed that the input meets all the specified conditions.
For example, suppose the user is required to enter a positive odd prime
number less than 100. You could enforce that with:
my $opnlt100 = prompt 'Enter your guess:',
-integer,
-must => { 'be odd' => 'odd',
'be in range' => [1..100],
'It must also be prime:' => \&isprime,
};
Note that, if the error message begins with anything except an uppercase
character, the prompt is reissued followed by the error message in
parentheses with the word ``must'' prepended (where appropriate).
Otherwise, if the error message does start with an uppercase character,
the prompt is not reissued and the error message is printed verbatim. So
a typical input sequence for the previous example might look like:
Enter your guess: 101
Enter your guess: (must be in range) 42
It must also be prime: 2
Enter your guess: (must be odd) 7
at which point, the call to prompt() would accept the input and return.
See also the -guarantee option,
which allows you to constrain inputs as they are typed, rather than
after they are entered.
- -r[STR]
-
- -ret[urn] [=> STR]
-
When <ENTER>/<RETURN> is pressed, prompt() usually echoes a carriage return.
However, if this option is given, prompt() echoes the specified string
instead. If the string is omitted, it defaults to "\n".
For example:
while (1) {
my $expr = prompt 'Calculate:', -ret=>' = ';
say evaluate($expr);
}
would prompt for something like this:
Calculate: 2*3+4^5_
and when the <ENTER>/<RETURN> key is pressed, respond with:
Calculate: 2*3+4^5 = 1030
Calculate: _
The string specified with -return is also automatically echoed if the
-single option is used. So if you
don't want the automatic carriage return that -single mode supplies,
specify -return=>"".
- -s
-
- -1
-
- -sing[le]
-
This option causes prompt() to return immediately once any single
character is input. The user does not have to push the <ENTER>/<RETURN>
key to complete the input operation. -single mode input is only
available if the Term::ReadKey module can be loaded.
By default, prompt() echoes the single character that is entered. Use
the -echo option to change or
prevent that.
# Let user navigate through maze by single, silent keypresses...
while ($nextdir = prompt "\n", -single, -echo, -guarantee=>qr/[nsew]/) {
move_player($nextdir);
}
Unless echoing has been disabled, by default prompt() also supplies a
carriage return after the input character. Use
the -return option to change
that behaviour. For example, this:
my $question = <<END_QUESTION;
Bast is the goddess of: (a) dogs (b) cats (c) cooking (d) war?
Your answer:
END_QUESTION
my $response = prompt $question, -1, -return=>' is ', -g=>['a'..'d'];
say $response eq $answer ? 'CORRECT' : 'incorrect';
prompts like this:
Bast is the goddess of: (a) dogs (b) cats (c) cooking (d) war?
Your answer: _
accepts a single character, like so:
Bast is the goddess of: (a) dogs (b) cats (c) cooking (d) war?
Your answer: b_
and completes the line thus:
Bast is the goddess of: (a) dogs (b) cats (c) cooking (d) war?
Your answer: b is CORRECT
_
- -v
-
- -verb[atim]
-
Normally, prompt() returns a special object that contains the text
input, the success value, and other information such as whether the
default was selected and whether the input operation timed out.
However, if you prefer to have prompt() just return the input text string
directly, you can specify this option.
Note however that, under -verbatim, the input is still
autochomped (unless you also specify
the -line option.
- -w
-
- -wipe[first]
-
If this option is present, prompt() prints 1000 newlines before
printing its prompt, effectively wiping the screen clear of other text.
If the -wipefirst variant is used, the wipe will only occur if the
particular call to prompt() is the first such call anywhere in your
program. This is useful if you'd like the screen cleared at the start of
input only, but you're not sure which call to prompt() will happen
first: just use -wipefirst on all possible initial calls and only the
actual first call will wipe the screen.
- -y[n] or -Y[N]
-
- -yes[no] or -Yes[No]
-
- -yes[no] => COUNT or -Yes[No] => COUNT
-
This option invokes a special mode that can be used to confirm (or deny)
something. If one of these options is specified, prompt still
returns the user's input, but the success or failure of the object returned
now depends on what the user types in.
A true result is returned if 'y' is the first character entered. If
the flag includes an n or N, a false result is returned if 'n'
is the first character entered (and any other input causes the prompt to
be reissued). If the option doesn't contain an n or N, any input
except 'y' is treated as a ``no'' and a false value is returned.
If the option is capitalized (-Y or -YN), the first letter of the
input must be likewise a capital (this is a handy means of slowing down
automatic unthinking y...``Oh no!'' responses to potentially serious
decisions).
This option is most often used in conjunction with the -single option, like
so:
$continue = prompt("Continue? ", -yn1);
so that the user can just hit y or n to continue, without having to hit
<ENTER>/<RETURN> as well.
If the optional COUNT argument is supplied, the prompting is repeated
that many times, with increasingly insistent requests for confirmation.
The answer must be ``yes'' in each case for the final result to be true.
For example:
$rm_star = prompt("Do you want to delete all files? ", -Yes=>3 );
might prompt:
Do you want to delete all files? Y
Really? Y
Are you sure? Y
You can bundle together any number of short-form options, including those that
take string arguments. For example, instead of writing:
if (prompt "Continue? ", -yes, -1, -t10, -dn) {
you could just write:
if (prompt "Continue? ", -y1t10dn) {...}
This often does not improve readability (as the preceding example
demonstrates), but is handy for common usages such as -y1 (``ask for
confirmation, don't require an <ENTER>/<RETURN>) or -vl
(''Return a verbatim and unchomped string``).
-_
The -_ option exists only to be an explicit no-op. It allows you to
specify short-form options that would otherwise be interpreted as Perl
file operators or other special constructs, simply by prepending or
appending a _ to them. For example:
my $input
= prompt -l_; # option -l, not the -l file operator.
The following single-letter options require an underscore to chaperone them
when they're on their own: -e, -l, -r, -s, -w, and -y.
However, an underscore is not required if two or more are bundled together.
Normally, in a void context, a call to prompt() issues a warning that
you are doing an input operation whose input is immediately thrown away.
There is, however, one situation where this useless use of prompt() in a
void context is actually useful:
say $data;
prompt('END OF DATA. Press any key to exit', -echo, -single);
exit;
Here, we're using prompt simply to pause the application after the data is
printed. It doesn't matter what the user types in; the typing itself is the
message (and the message is ``move along'').
In such cases, the ``useless use...'' warning can be suppressed using the
-void option:
say $data;
prompt('END OF DATA. Press any key to exit', -echo, -single, -void);
exit;
IO::Prompter provides a mechanism with which you can ``script'' a sequence of
inputs to an application. This is particularly useful when demonstrating
software during a presentation, as you do not have to remember what to type,
or concentrate on typing at all.
If you pass a string as an argument to use IO::Prompter, the
individual lines of that string are used as successive input lines to
any call to prompt(). So for example, you could specify several sets
of input data, like so:
use IO::Prompter <<END_DATA
Leslie
45
165
Jessie
28
178
Dana
12
120
END_DATA
and then read this data in an input loop:
while (my $name = prompt 'Name:') {
my $age = prompt 'Age:';
my $height = prompt 'Height:';
process($name, $age, $height);
}
Because the use IO::Prompter supplies input data,
the three calls to prompt() will no longer read
data from *ARGV. Instead they will read it from
the supplied input data.
Moreover, each call to prompt() will simulate the typing-in process
automatically. That is, prompt() uses a special input mode where,
each time you press a keyboard letter, it echoes not that character, but
rather the next character from the specified input. The effect is that
you can just type on the keyboard at random, but have the correct input
appear. This greatly increases the convincingness of the simulation.
If at any point, you hit <ENTER>/<RETURN> on the keyboard, prompt()
finishes typing in the input for you (using a realistic typing speed),
and returns the input string. So you can also just hit <ENTER>/<RETURN>
when the prompt first appears, to have the entire line of input typed
for you.
Alternatively, if you hit <ESC> at any point, prompt() escapes
from the simulated input mode for that particular call to prompt(),
and allows you to (temporarily) type text in directly. If you enter only
a single <ESC>, then prompt() throws away the current line of
simulated input; if you enter two <ESC>'s, the simulated input is
merely deferred to the next call to prompt().
All these keyboard behaviours require the Term::ReadKey module to be
available. If it isn't, prompt() falls back on a simpler simulation,
where it just autotypes each entire line for you and pauses at the
end of the line, waiting for you to hit <ENTER>/<RETURN> manually.
Note that any line of the simulated input that begins with
a <CTRL-D> or <CTRL-Z> is treated as an input failure (just as
if you'd typed that character as input).
All non-fatal diagnostics can be disabled using a no warnings with the
appropriate category.
- prompt(): Can't open *ARGV: %s
-
(F) By default,
prompt() attempts to read input from
the *ARGV filehandle. However, it failed to open
that filehandle. The reason is specified at the end of
the message.
prompt(): Missing value for %s (expected %s)prompt(): Missing value for %s (expected %s)
-
(F) A named option that requires an argument was specified,
but no argument was provided after the option. See
Summary of options.
prompt(): Invalid value for %s (expected %s)prompt(): Invalid value for %s (expected %s)
-
(F) The named option specified expects an particular type
of argument, but found one of an incompatible type
instead. See Summary of options.
prompt(): Unknown option %s ignoredprompt(): Unknown option %s ignored
-
(W misc)
prompt() was passed a string starting with
a hyphen, but could not parse that string as a
valid option. The option may have been misspelt.
Alternatively, if the string was supposed to be
(part of) the prompt, it will be necessary to use
the -prompt option to specify it.
prompt(): Unexpected argument (% ref) ignoredprompt(): Unexpected argument (% ref) ignored
-
(W reserved)
prompt() was passed a reference to
an array or hash or subroutine in a position
where an option flag or a prompt string was
expected. This may indicate that a string
variable in the argument list didn't contain
what was expected, or a reference variable was
not properly dereferenced. Alternatively, the
argument may have been intended as the
argument to an option, but has become
separated from it somehow, or perhaps the
option was deleted without removing the
argument as well.
Useless use of prompt() in void contextUseless use of prompt() in void context
-
(W void)
prompt() was called but its return value was
not stored or used in any way. Since the
subroutine has no side effects in void context,
calling it this way achieves nothing. Either make
use of the return value directly or, if the usage
is deliberate, put a scalar in front of the
call to remove the void context.
prompt(): -default value does not satisfy -must constraintsprompt(): -default value does not satisfy -must constraints
-
(W misc) The
-must flag was used to specify one or more
input constraints. The -default flag was also
specified. Unfortunately, the default value
provided did not satisfy the requirements
specified by the -must flag. The call to
prompt() will still go ahead (after issuing the
warning), but the default value will never be
returned, since the constraint check will reject
it. It is probably better simply to include the
default value in the list of constraints.
prompt(): -keyletters found too many defaultsprompt(): -keyletters found too many defaults
-
(W ambiguous) The
-keyletters option was specified,
but analysis of the prompt revealed two or
more character sequences enclosed in square
brackets. Since such sequences are taken to
indicate a default value, having two or more
makes the default ambiguous. The prompt
should be rewritten with no more than one set
of square brackets.
- Warning: next input will be in plaintext
-
(W bareword) The
prompt() subroutine was called with
the -echo flag, but the Term::ReadKey
module was not available to implement this
feature. The input will proceed as normal, but
this warning is issued to ensure that the user
doesn't type in something secret, expecting it
to remain hidden, which it won't.
prompt(): Too many menu items. Ignoring the final %dprompt(): Too many menu items. Ignoring the final %d
-
(W misc) A
-menu was specified with more than 52 choices.
Because, by default, menus use upper and lower-
case alphabetic characters as their selectors,
there were no available selectors for the extra
items after the first 52. Either reduce the number
of choices to 52 or less, or else add the
-number option to use numeric selectors instead.
IO::Prompter can be configured by setting any of the following
environment variables:
- $IO_PROMPTER_COMPLETE_KEY
-
Specifies the key used to initiate
user-specified completions.
Defaults to <TAB>
- $IO_PROMPTER_HISTORY_KEY
-
Specifies the key used to initiate
history completions.
Defaults to <CTRL-R>
- $IO_PROMPTER_COMPLETE_MODES
-
Specifies the
response sequence
for user-defined completions. Defaults to
'list+longest full'
- $IO_PROMPTER_HISTORY_MODES
-
Specifies the
response sequence
for history completions. Defaults to
'full'.
Requires the Contextual::Return module.
The module also works much better if Term::ReadKey is available
(though this is not essential).
This module does not play well with Moose (or more specifically, with
Moose::Exporter) because both of them try to play sneaky games with
Scalar::Util::blessed.
The current solution is to make sure that you load Moose before
loading IO::Prompter. Even just doing this:
use Moose ();
use IO::Prompter;
is sufficient.
No unresolved bugs have been reported.
Please report any bugs or feature requests to
bug-io-prompter@rt.cpan.org, or through the web interface at
http://rt.cpan.org.
Damian Conway <DCONWAY@CPAN.org>
Copyright (c) 2009, Damian Conway <DCONWAY@CPAN.org>.
All rights reserved.
This module is free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See perlartistic.
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE SOFTWARE ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
NECESSARY SERVICING, REPAIR, OR CORRECTION.
IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE
LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL,
OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.
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