Provided by: libshell-posix-select-perl_0.05-2_all 
NAME
Shell::POSIX::Select - The POSIX Shell's "select" loop for Perl
PURPOSE
This module implements the "select" loop of the "POSIX" shells (Bash, Korn, and
derivatives) for Perl. That loop is unique in two ways: it's by far the friendliest
feature of any UNIX shell, and it's the only UNIX shell loop that's missing from the Perl
language. Until now!
What's so great about this loop? It automates the generation of a numbered menu of
choices, prompts for a choice, proofreads that choice and complains if it's invalid (at
least in this enhanced implementation), and executes a code-block with a variable set to
the chosen value. That saves a lot of coding for interactive programs -- especially if
the menu consists of many values!
The benefit of bringing this loop to Perl is that it obviates the need for future
programmers to reinvent the Choose-From-A-Menu wheel.
SYNOPSIS
select [ [my|local|our] scalar_var ] ( [LIST] ) { [CODE] }
In the above, the enclosing square brackets (not typed) identify optional elements, and
vertical bars separate mutually-exclusive choices:
The required elements are the keyword "select", the parentheses, and the curly braces.
See "SYNTAX" for details.
ELEMENTARY EXAMPLES
NOTE: All non-trivial programming examples shown in this document are distributed with
this module, in the Scripts directory. "ADDITIONAL EXAMPLES", covering more features, are
shown below.
ship2me.plx
use Shell::POSIX::Select;
select $shipper ( 'UPS', 'FedEx' ) {
print "\nYou chose: $shipper\n";
last;
}
ship ($shipper, $ARGV[0]); # prints confirmation message
Screen
ship2me.plx '42 hemp toothbrushes' # program invocation
1) UPS 2) FedEx
Enter number of choice: 2
You chose: FedEx
Your order has been processed. Thanks for your business!
ship2me2.plx
This variation on the preceding example shows how to use a custom menu-heading and
interactive prompt.
use Shell::POSIX::Select qw($Heading $Prompt);
$Heading='Select a Shipper' ;
$Prompt='Enter Vendor Number: ' ;
select $shipper ( 'UPS', 'FedEx' ) {
print "\nYou chose: $shipper\n";
last;
}
ship ($shipper, $ARGV[0]); # prints confirmation message
Screen
ship2me2.plx '42 hemp toothbrushes'
Select a Shipper
1) UPS 2) FedEx
Enter Vendor Number: 2
You chose: FedEx
Your order has been processed. Thanks for your business!
SYNTAX
Loop Structure
Supported invocation formats include the following:
use Shell::POSIX::Select ;
select () { } # Form 0
select () { CODE } # Form 1
select (LIST) { CODE } # Form 2
select $var (LIST) { CODE } # Form 3
select my $var (LIST) { CODE } # Form 4
select our $var (LIST) { CODE } # Form 5
select local $var (LIST) { CODE } # Form 6
If the loop variable is omitted (as in Forms 0, 1 and 2 above), it defaults to $_,
"local"ized to the loop's scope. If the LIST is omitted (as in Forms 0 and 1), @ARGV is
used by default, unless the loop occurs within a subroutine, in which case @_ is used
instead. If CODE is omitted (as in Form 0, it defaults to a statement that prints the
loop variable.
The cases shown above are merely examples; all reasonable permutations are permitted,
including:
select $var ( ) { CODE }
select local $var (LIST) { }
The only form that's not allowed is one that specifies the loop-variable's declarator
without naming the loop variable, as in:
select our () { } # WRONG! Must name variable with declarator!
The Loop variable
See "SCOPING ISSUES" for full details about the implications of different types of
declarations for the loop variable.
The $Reply Variable
When the interactive user responds to the "select" loop's prompt with a valid input (i.e.,
a number in the correct range), the variable $Reply is set within the loop to that number.
Of course, the actual item selected is usually of great interest than its number in the
menu, but there are cases in which access to this number is useful (see "menu_ls.plx" for
an example).
OVERVIEW
This loop is syntactically similar to Perl's "foreach" loop, and functionally related, so
we'll describe it in those terms.
foreach $var ( LIST ) { CODE }
The job of "foreach" is to run one iteration of CODE for each LIST-item, with the current
item's value placed in "local"ized $var (or if the variable is missing, "local"ized $_).
select $var ( LIST ) { CODE }
In contrast, the "select" loop displays a numbered menu of LIST-items on the screen,
prompts for (numerical) input, and then runs an iteration with $var being set that
number's LIST-item.
In other words, "select" is like an interactive, multiple-choice version of a "foreach"
loop. And that's cool! What's not so cool is that "select" is also the only UNIX shell
loop that's been left out of the Perl language. Until now!
This module implements the "select" loop of the Korn and Bash ("POSIX") shells for Perl.
It accomplishes this through Filter::Simple's Source Code Filtering service, allowing the
programmer to blithely proceed as if this control feature existed natively in Perl.
The Bash and Korn shells differ slightly in their handling of "select" loops, primarily
with respect to the layout of the on-screen menu. This implementation currently follows
the Korn shell version most closely (but see "TODO-LIST" for notes on planned
enhancements).
ENHANCEMENTS
Although the shell doesn't allow the loop variable to be omitted, for compliance with
Perlish expectations, the "select" loop uses "local"ized $_ by default (as does the native
"foreach" loop). See "SYNTAX" for details.
The interface and behavior of the Shell versions has been retained where deemed desirable,
and sensibly modified along Perlish lines elsewhere. Accordingly, the (primary) default
LIST is @ARGV (paralleling the Shell's "$@"), menu prompts can be customized by having the
script import and set $Prompt (paralleling the Shell's $PS3), and the user's response to
the prompt appears in the variable $Reply (paralleling the Shell's $REPLY), "local"ized to
the loop.
A deficiency of the shell implementation is the inability of the user to provide a heading
for each "select" menu. Sure, the shell programmer can echo a heading before the loop is
entered and the menu is displayed, but that approach doesn't help when an Outer loop is
reentered on departure from an Inner loop, because the echo preceding the Outer loop won't
be re-executed.
A similar deficiency surrounds the handling of a custom prompt string, and the need to
automatically display it on moving from an inner loop to an outer one.
To address these deficiencies, this implementation provides the option of having a heading
and prompt bound to each "select" loop. See "IMPORTS AND OPTIONS" for details.
Headings and prompts are displayed in reverse video on the terminal, if possible, to make
them more visually distinct.
Some shell versions simply ignore bad input, such as the entry of a number outside the
menu's valid range, or alphabetic input. I can't imagine any argument in favor of this
behavior being desirable when input is coming from a terminal, so this implementation
gives clear warning messages for such cases by default (see "Warnings" for details).
After a menu's initial prompt is issued, some shell versions don't show it again unless
the user enters an empty line. This is desirable in cases where the menu is sufficiently
large as to cause preceding output to scroll off the screen, and undesirable otherwise.
Accordingly, an option is provided to enable or disable automatic prompting (see
"Prompts").
This implementation always issues a fresh prompt when a terminal user submits EOF as input
to a nested "select" loop. In such cases, experience shows it's critical to reissue the
menu of the outer loop before accepting any more input.
SCOPING ISSUES
If the loop variable is named and provided with a declarator ("my", "our", or "local"),
the variable is scoped within the loop using that type of declaration. But if the
variable is named but lacks a declarator, no declaration is applied to the variable.
This allows, for example, a variable declared as private above the loop to be accessible
from within the loop, and beyond it, and one declared as private for the loop to be
confined to it:
select my $loopvar ( ) { }
print "$loopvar DOES NOT RETAIN last value from loop here\n";
-------------------------------------------------------------
my $loopvar;
select $loopvar ( ) { }
print "$loopvar RETAINS last value from loop here\n";
With this design, "select" behaves differently than the native "foreach" loop, which
nowadays employs automatic localization.
foreach $othervar ( ) { } # variable localized automatically
print "$othervar DOES NOT RETAIN last value from loop here\n";
select $othervar ( ) { } # variable in scope, or global
print "$othervar RETAINS last value from loop here\n";
This difference in the treatment of variables is intentional, and appropriate. That's
because the whole point of "select" is to let the user choose a value from a list, so it's
often critically important to be able to see, even outside the loop, the value assigned to
the loop variable.
In contrast, it's usually considered undesirable and unnecessary for the value of the
"foreach" loop's variable to be visible outside the loop, because in most cases it will
simply be that of the last element in the list.
Of course, in situations where the "foreach"-like behavior of implicit "local"ization is
desired, the programmer has the option of declaring the "select" loop's variable as
"local".
Another deficiency of the Shell versions is that it's difficult for the programmer to
differentiate between a "select" loop being exited via "last", versus the loop detecting
EOF on input. To correct this situation, the variable $Eof can be imported and checked
for a TRUE value upon exit from a "select" loop (see "Eof Detection").
IMPORTS AND OPTIONS
Syntax
use Shell::POSIX::Select (
'$Prompt', # to customize per-menu prompt
'$Heading', # to customize per-menu heading
'$Eof', # T/F for Eof detection
# Variables must come first, then key/value options
prompt => 'Enter number of choice:', # or 'whatever:'
style => 'Bash', # or 'Korn'
warnings => 1, # or 0
debug => 0, # or 1-5
logging => 0, # or 1
testmode => <unset>, # or 'make', or 'foreach'
);
NOTE: The values shown for options are the defaults, except for "testmode", which doesn't
have one.
Prompts
There are two ways to customize the prompt used to solicit choices from "select" menus;
through use of the prompt option, which applies to all loops, or the $Prompt variable,
which can be set independently for each loop.
The prompt option
The "prompt" option is intended for use in programs that either contain a single "select"
loop, or are content to use the same prompt for every loop. It allows a custom
interactive prompt to be set in the use statement.
The prompt string should not end in a whitespace character, because that doesn't look nice
when the prompt is highlighted for display (usually in reverse video). To offset the
cursor from the prompt's end, one space is inserted automatically after display
highlighting has been turned off.
If the environment variable $ENV{Shell_POSIX_Select_prompt} is present, its value
overrides the one in the use statement.
The default prompt is "Enter number of choice:". To get the same prompt as provided by
the Korn or Bash shell, use "prompt =>> Korn" or "prompt => Bash".
The $Prompt variable
The programmer may also modify the prompt during execution, which may be desirable with
nested loops that require different user instructions. This is accomplished by importing
the $Prompt variable, and setting it to the desired prompt string before entering the
loop. Note that imported variables have to be listed as the initial arguments to the
"use" directive, and properly quoted. See "order.plx" for an example.
NOTE: If the program's input channel is not connected to a terminal, prompting is
automatically disabled (since there's no point in soliciting input from a pipe!).
$Heading
The programmer has the option of binding a heading to each loop's menu, by importing
$Heading and setting it just before entering the associated loop. See "order.plx" for an
example.
$Eof
A common concern with the Shell's "select" loop is distinguishing between cases where a
loop ends due to EOF detection, versus the execution of "break" (like Perl's "last").
Although the Shell programmer can check the $REPLY variable to make this distinction, this
implementation localizes its version of that variable ($Reply) to the loop, obviating that
possibility.
Therefore, to make EOF detection as convenient and easy as possible, the programmer may
import $Eof and check it for a TRUE value after a "select" loop. See "lc_filename.plx"
for a programming example.
Styles
The "style" options Korn and Bash can be used to request a more Kornish or Bashlike style
of behavior. Currently, the only difference is that the former disables, and the latter
enables, prompting for every input. A value can be provided for the "style" option using
an argument of the form "style => 'Korn'" to the "use" directive. The default setting is
"Bash". If the environment variable $ENV{Shell_POSIX_Select_style} is set to "Korn" or
"Bash", its value overrides the one provided with the use statement.
Warnings
The "warnings" option, whose values range from 0 to 1, enables informational messages
meant to help the interactive user provide correct inputs. The default setting is 1,
which provides warnings about incorrect responses to menu prompts (non-numeric, out of
range, etc.). Level 0 turns these off.
If the environment variable $ENV{Shell_POSIX_Select_warnings} is present, its value takes
precedence.
Logging
The "logging" option, whose value ranges from 0 to 1, causes informational messages and
source code to be saved in temporary files (primarily for debugging purposes).
The default setting is 0, which disables logging.
If the environment variable $ENV{Shell_POSIX_Select_logging} is present, its value takes
precedence.
Debug
The "debug" option, whose values range from 0 to 9, enables informational messages to aid
in identifying bugs. If the environment variable $ENV{Shell_POSIX_Select_debug} is
present, and set to one of the acceptable values, it takes precedence.
This option is primarly intended for the author's use, but users who find bugs may want to
enable it and email the output to "AUTHOR". But before concluding that the problem is
truly a bug in this module, please confirm that the program runs correctly with the option
"testmode => foreach" enabled (see "Testmode").
Testmode
The "testmode" option, whose values are 'make' and 'foreach', changes the way the program
is executed. The 'make' option is used during the module's installation, and causes the
program to dump the modified source code and screen display to files, and then stop
(rather than interacting with the user).
If the environment variable $ENV{Shell_POSIX_Select_testmode} is present, and set to one
of the acceptable values, it takes precedence.
With the "foreach" option enabled, the program simply translates occurrences of "select"
into "foreach", which provides a useful method for checking that the program is
syntactically correct before any serious filtering has been applied (which can introduce
syntax errors). This works because the two loops, in their full forms, have identical
syntax.
Note that before you use "testmode => foreach", you must fill in any missing parts that
are required by "foreach".
For instance,
" select () {}"
must be rewritten as follows, to explicitly show "@ARGV" (assuming it's not in a
subroutine) and "print":
" foreach (@ARGV) { print; }"
ADDITIONAL EXAMPLES
NOTE: All non-trivial programming examples shown in this document are distributed with
this module, in the Scripts directory. See "ELEMENTARY EXAMPLES" for simpler uses of
"select".
pick_file.plx
This program lets the user choose filenames to be sent to the output. It's sort of like
an interactive Perl "grep" function, with a live user providing the filtering service. As
illustrated below, it could be used with Shell command substitution to provide selected
arguments to a command.
use Shell::POSIX::Select (
prompt => 'Pick File(s):' ,
style => 'Korn' # for automatic prompting
);
select ( <*> ) { }
Screen
lp `pick_file`> # Using UNIX-like OS
1) memo1.txt 2) memo2.txt 3) memo3.txt
4) junk1.txt 5) junk2.txt 6) junk3.txt
Pick File(s): 4
Pick File(s): 2
Pick File(s): ^D
request id is yumpy@guru+587
browse_images.plx
Here's a simple yet highly useful script. It displays a menu of all the image files in
the current directory, and then displays the chosen ones on-screen using a backgrounded
image viewer. It uses Perl's "grep" to filter-out filenames that don't end in the desired
extensions.
use Shell::POSIX::Select ;
$viewer='xv'; # Popular image viewer
select ( grep /\.(jpg|gif|tif|png)$/i, <*> ) {
system "$viewer $_ &" ; # run viewer in background
}
perl_man.plx
Back in the olden days, we only had one Perl man-page. It was voluminous, but at least you
knew what argument to give the man command to get the documentaton.
Now we have over a hundred Perl man pages, with unpredictable names that are difficult to
remember. Here's the program I use that allows me to select the man-page of interest from
a menu.
use Shell::POSIX::Select ;
# Extract man-page names from the TOC portion of the output of "perldoc perl"
select $manpage ( sort ( `perldoc perl` =~ /^\s+(perl\w+)\s/mg) ) {
system "perldoc '$manpage'" ;
}
Screen
1) perl5004delta 2) perl5005delta 3) perl561delta
4) perl56delta 5) perl570delta 6) perl571delta
. . .
(This large menu spans multiple screens, but all parts can be accessed
using your normal terminal scrolling facility.)
Enter number of choice: 6
PERL571DELTA(1) Perl Programmers Reference Guide
NAME
perl571delta - what's new for perl v5.7.1
DESCRIPTION
This document describes differences between the 5.7.0
release and the 5.7.1 release.
. . .
pick.plx
This more general "pick"-ing program lets the user make selections from arguments, if
they're present, or else input, in the spirit of Perl's "-n" invocation option and "<>"
input operator.
use Shell::POSIX::Select ;
BEGIN {
if (@ARGV) {
@choices=@ARGV ;
}
else { # if no args, get choices from input
@choices=<STDIN> or die "$0: No data\n";
chomp @choices ;
# STDIN already returned EOF, so must reopen
# for terminal before menu interaction
open STDIN, "/dev/tty" or
die "$0: Failed to open STDIN, $!" ; # UNIX example
}
}
select ( @choices ) { } # prints selections to output
Sample invocations (UNIX-like system)
lp `pick *.txt` # same output as shown for "pick_file"
find . -name '*.plx' -print | pick | xargs lp # includes sub-dirs
who |
awk '{ print $1 }' | # isolate user names
pick | # select user names
Mail -s 'Promote these people!' boss
delete_file.plx
In this program, the user selects a filename to be deleted. The outer loop is used to
refresh the list, so the file deleted on the previous iteration gets removed from the next
menu. The outer loop is labeled (as "OUTER"), so that the inner loop can refer to it when
necessary.
use Shell::POSIX::Select (
'$Eof', # for ^D detection
prompt=>'Choose file for deletion:'
) ;
OUTER:
while ( @files=<*.py> ) { # collect serpentine files
select ( @files ) { # prompt for deletions
print STDERR "Really delete $_? [y/n]: " ;
my $answer = <STDIN> ; # ^D sets $Eof below
defined $answer or last OUTER ; # exit on ^D
$answer eq "y\n" and unlink and last ;
}
$Eof and last;
}
lc_filename.plx
This example shows the benefit of importing $Eof, so the outer loop can be exited when the
user supplies "^D" to the inner one.
Here's how it works. If the rename succeeds in the inner loop, execution of "last" breaks
out of the "select" loop; $Eof will then be evaluated as FALSE, and the "while" loop will
start a new "select" loop, with a (depleted) filename menu. But if the user presses "^D"
to the menu prompt, $Eof will test as TRUE, triggering the exit from the "while" loop.
use Shell::POSIX::Select (
'$Eof' ,
prompt => 'Enter number (^D to exit):'
style => 'Korn' # for automatic prompting
);
# Rename selected files from current dir to lowercase
while ( @files=<*[A-Z]*> ) { # refreshes select's menu
select ( @files ) { # skip fully lower-case names
if (rename $_, "\L$_") {
last ;
}
else {
warn "$0: rename failed for $_: $!\n";
}
}
$Eof and last ; # Handle ^D to menu prompt
}
Screen
lc_filename.plx
1) Abe.memo 2) Zeke.memo
Enter number (^D to exit): 1
1) Zeke.memo
Enter number (^D to exit): ^D
order.plx
This program sets a custom prompt and heading for each of its two loops, and shows the use
of a label on the outer loop.
use Shell::POSIX::Select qw($Prompt $Heading);
$Heading="\n\nQuantity Menu:";
$Prompt="Choose Quantity:";
OUTER:
select my $quantity (1..4) {
$Heading="\nSize Menu:" ;
$Prompt='Choose Size:' ;
select my $size ( qw (L XL) ) {
print "You chose $quantity units of size $size\n" ;
last OUTER ; # Order is complete
}
}
Screen
order.plx
Quantity Menu:
1) 1 2) 2 3) 3 4) 4
Choose Quantity: 4
Size Menu:
1) L 2) XL
Choose Size: ^D (changed my mind about the quantity)
Quantity Menu:
1) 1 2) 2 3) 3 4) 4
Choose Quantity: 2
Size Menu:
1) L 2) XL
Choose Size: 2
You chose 2 units of size XL
browse_records.plx
This program shows how you can implement a "record browser", that builds a menu from the
designated field of each record, and then shows the record associated with the selected
field.
To use a familiar example, we'll browse the UNIX password file by user-name.
use Shell::POSIX::Select ( style => 'Korn' );
if (@ARGV != 2 and @ARGV != 3) {
die "Usage: $0 fieldnum filename [delimiter]" ;
}
# Could also use Getopt:* module for option parsing
( $field, $file, $delim) = @ARGV ;
if ( ! defined $delim ) {
$delim='[\040\t]+' # SP/TAB sequences
}
$field-- ; # 2->1, 1->0, etc., for 0-based indexing
foreach ( `cat "$file"` ) {
# field is the key in the hash, value is entire record
$f2r{ (split /$delim/, $_)[ $field ] } = $_ ;
}
# Show specified fields in menu, and display associated records
select $record ( sort keys %f2r ) {
print "$f2r{$record}\n" ;
}
Screen
browsrec.plx '1' /etc/passwd ':'
1) at 2) bin 3) contix 4) daemon 5) ftp 6) games
7) lp 8) mail 9) man 10) named 11) news 12) nobody
13) pop 14) postfix 15) root 16) spug 17) sshd 18) tim
Enter number of choice: 18
tim:x:213:100:Tim Maher:/home/tim:/bin/bash
Enter number of choice: ^D
menu_ls.plx
This program shows a prototype for a menu-oriented front end to a UNIX command, that
prompts the user for command-option choices, assembles the requested command, and then
runs it.
It employs the user's numeric choice, stored in the $Reply variable, to extract from an
array the command option associated with each option description.
use Shell::POSIX::Select qw($Heading $Prompt $Eof) ;
# following avoids used-only once warning
my ($type, $format) ;
# Would be more Perlish to associate choices with options
# via a Hash, but this approach demonstrates $Reply variable
@formats = ( 'regular', 'long' ) ;
@fmt_opt = ( '', '-l' ) ;
@types = ( 'only non-hidden', 'all files' ) ;
@typ_opt = ( '', '-a' , ) ;
print "** LS-Command Composer **\n\n" ;
$Heading="\n**** Style Menu ****" ;
$Prompt= "Choose listing style:" ;
OUTER:
select $format ( @formats ) {
$user_format=$fmt_opt[ $Reply - 1 ] ;
$Heading="\n**** File Menu ****" ;
$Prompt="Choose files to list:" ;
select $type ( @types ) { # ^D restarts OUTER
$user_type=$typ_opt[ $Reply - 1 ] ;
last OUTER ; # leave loops once final choice obtained
}
}
$Eof and exit ; # handle ^D to OUTER
# Now construct user's command
$command="ls $user_format $user_type" ;
# Show command, for educational value
warn "\nPress <ENTER> to execute \"$command\"\n" ;
# Now wait for input, then run command
defined <> or print "\n" and exit ;
system $command ; # finally, run the command
Screen
menu_ls.plx
** LS-Command Composer **
1) regular 2) long
Choose listing format: 2
1) only non-hidden 2) all files
Choose files to list: 2
Press <ENTER> to execute "ls -l -a" <ENTER>
total 13439
-rw-r--r-- 1 yumpy gurus 1083 Feb 4 15:41 README
-rw-rw-r-- 6 yumpy gurus 277 Dec 17 14:36 .exrc.mmkeys
-rw-rw-r-- 7 yumpy gurus 285 Jan 16 18:45 .exrc.podkeys
$
BUGS
UNIX Orientation
I've been a UNIX programmer since 1976, and a Linux proponent since 1992, so it's most
natural for me to program for those platforms. Accordingly, this early release has some
minor features that are only allowed, or perhaps only entirely functional, on UNIX-like
systems. I'm open to suggestions on how to implement some of these features in a more
portable manner.
Some of the programming examples are also UNIX oriented, but it should be easy enough for
those specializing on other platforms to make the necessary adapations. 8-}
Terminal Display Modes
These have been tested under UNIX/Linux, and work as expected, using tput. When time
permits, I'll convert to a portable implementation that will support other OSs.
Incorrect Line Numbers in Warnings
Because this module inserts new source code into your program, Perl messages that
reference line numbers will refer to a different source file than you wrote. For this
reason, only messages referring to lines before the first "select" loop in your program
will be correct.
If you're on a UNIX-like system, by enabling the "debugging" and "logging" options (see
"Debug" and "Logging"), you can get an on-screen report of the proper offset to apply to
interpret the line numbers of the source code that gets dumped to the /tmp/SELECT_source
file. Of course, if everything works correctly, you'll have little reason to look at the
source. 8-}
Comments can Interfere with Filtering
Because of the way Filter::Simple works, ostensibly "commented-out" "select" loops like
the following can actually break your program:
# select (@ARGV)
# { ; }
select (@ARGV) { ; }
A future version of Filter::Simple (or more precisely Text::Balanced, on which on which it
depends) may correct this problem.
In any case, there's an easy workaround for the commented-out select loop problem; just
change select into eslect when you comment it out, and there'll be no problem.
For other problems involving troublesome text within comments, see "Failure to Identify
select Loops".
Failure to Identify "select" Loops
When a properly formed "select" loop appears in certain contexts, such as before a line
containing certain patterns of dollar signs or quotes, it will not be properly identified
and translated into standard Perl.
The failure of the filtering routine to rewrite the loop causes the compiler to issue the
following fatal error when it sees the { following the (LIST):
syntax error at filename line X, near ") {"
This of course prevents the program from running.
The problem is either a bug in Filter::Simple, or one of the modules on which it depends.
Until this is resolved, you may be able to handle such cases by explicitly turning
filtering off before the offending code is encountered, using the no directive:
use Shell::POSIX::Select; # filtering ON
select (@names) { print ; }
no Shell::POSIX::Select; # filtering OFF
# $X$
Restrictions on Loop-variable Names
Due to a bug in most versions of Text::Balanced, loop-variable names that look like Perl
operators, including $m, $a, $s, $y, $tr, $qq, $qw, $qr, and $qx, and possibly others,
cause syntax errors. Newer versions of that module (unreleased at the time of this
writing) have corrected this problem, so download the latest version if you must use such
names.
Please Report Bugs!
This is a non-trivial program, that does some fairly complex parsing and data munging, so
I'm sure there are some latent bugs awaiting your discovery. Please share them with me,
by emailing the offending code, and/or the diagnostic messages enabled by the debug option
setting (see "IMPORTS AND OPTIONS").
TODO-LIST
More Shell-like Menus
In a future release, there could be options for more accurately emulating Bash and Korn-
style behavior, if anybody cares (the main difference is in how the items are ordered in
the menus).
More Extensive Test Suite
More tests are needed, especially for the complex and tricky cases.
MODULE DEPENDENCIES
File::Spec::Functions
Text::Balanced
Filter::Simple
EXPORTS: Default
$Reply
This variable is "local"ized to each "select" loop, and provides the menu-number of the
most recent valid selection. For an example of its use, see "menu_ls.plx".
EXPORTS: Optional
$Heading
$Prompt
$Eof
See "IMPORTS AND OPTIONS" for details.
SCRIPTS
browse_images
browse_jpeg
browse_records
delete_file
lc_filename
long_listem
menu_ls
order
perl_man
pick
pick_file
AUTHOR
Tim Maher
Consultix
yumpy@cpan.org
http://www.teachmeperl.com
ACKNOWLEDGEMENTS
I probably never would have even attempted to write this module if it weren't for the
provision of Filter::Simple by Damian Conway, which I ruthlessly exploited to make a hard
job easy.
The Damian also gave useful tips during the module's development, for which I'm grateful.
I definitely wouldn't have ever written this module, if I hadn't found myself writing a
chapter on Looping for my upcoming Manning Publications book, and once again lamenting the
fact that the most friendly Shell loop was still missing from Perl. So in a fit of zeal,
I vowed to rectify that oversight!
I hope you find this module as useful as I do! 8-}
For more examples of how this loop can be used in Perl programs, watch for my upcoming
book, Minimal Perl: for Shell Users and Programmers (see
<http://teachmeperl.com/mp4sh.html>) in early fall, 2003.
SEE ALSO
man ksh # on UNIX or UNIX-like systems
man bash # on UNIX or UNIX-like systems
DON'T SEE ALSO
perldoc -f select, which has nothing to do with this module (the names just happen to
match up).
VERSION
This document describes version 0.05.
LICENSE
Copyright (C) 2002-2003, Timothy F. Maher. All rights reserved.
This module is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.