libscriptalicious-perl 1.16-1 / usr / share / perl5 / Scriptalicious.pod

=head1 NAME

Scriptalicious - Make scripts more delicious to SysAdmins

=head1 SYNOPSIS

 use Scriptalicious
      -progname => "pu";
 
 our $VERSION = "1.00";
 
 my $url = ".";
 getopt getconf("u|url" => \$url);
 
 run("echo", "doing something with $url");
 my $output = capture("svn", "info", $url);
 
 __END__
 
 =head1 NAME
 
 pu - an uncarved block of wood
 
 =head1 SYNOPSIS
 
 pu [options] arguments
 
 =head1 DESCRIPTION
 
 This script's function is to be a blank example that many
 great and simple scripts may be built upon.
 
 Remember, you cannot carve rotten wood.
 
 =head1 COMMAND LINE OPTIONS
 
 =over
 
 =item B<-h, --help>
 
 Display a program usage screen and exit.
 
 =item B<-V, --version>
 
 Display program version and exit.
 
 =item B<-v, --verbose>
 
 Verbose command execution, displaying things like the
 commands run, their output, etc.
 
 =item B<-q, --quiet>
 
 Suppress all normal program output; only display errors and
 warnings.
 
 =item B<-d, --debug>
 
 Display output to help someone debug this script, not the
 process going on.
 
 =back

=head1 DESCRIPTION

This module helps you write scripts that conform to best common
practices, quickly.  Just include the above as a template, and your
script will accept all of the options that are included in the manual
page, as well as summarising them when you use the C<-h> option.

(Unfortunately, it is not possible to have a `use' dependency
automatically add structure to your POD yet, so you have to include
the above manually.  If you want your help message and Perldoc to be
meaningful, that is.)

Shortcuts are provided to help you abort or die with various error
conditions; all of which print the name of the program running (taken
from C<$0> if not passed).  The motive for this is that "small"
scripts tend to just get written and forgotten; so, when you have a
larger system that is built out of lots of these pieces it is
sometimes guesswork figuring out which script a printed message comes
from!

For instance, if your program is called with invalid arguments, you
may simply call C<abort> with a one-line message saying what the
particular problem was.  When the script is run, it will invite the
person running the script to try to use the C<--help> option, which
gives them a summary and in turn invites them to read the Perldoc.
So, it reads well in the source;

  @ARGV and abort "unexpected arguments: @ARGV";
  $file or abort "no filename supplied";

And in the output;

  somescript: no filename supplied!
  Try `somescript --help' for a summary of options

On the other hand, if you call C<barf>, then it is considered to be a
hard run-time failure, and the invitation to read the C<--help> page
to get usage not given.  Also, the messages are much tidier than you
get with C<die> et al.

  open FOO, "<$file" or barf "failed to open $file; $!";

Which will print:

  somescript: failed to open somefile; Permission denied

Scriptalicious has no I<hard> dependencies; all the methods, save
reading passwords from the user, will work in the absence of extra
installed modules on all versions of Perl from 5.6.0 onwards.

To avoid unnecessary explicit importing of symbols, the following
symbols and functions are exported into the caller's namespace:

=over

=item C<$VERBOSE>

Set to 0 by default, and 1 if C<-v> or C<--verbose> was found during
the call to C<getopt()>.  Extra C<-v>'s or C<--debug> will push this
variable higher.  If C<-q> or C<--quiet> is specified, this will be
less than one.

=item C<$PROGNAME>

It is recommended that you only ever read this variable, and pass it
in via the import.  This is not automatically extracted from the POD
for performance reasons.

=item C<$CONFIG>

Name of the configuration file.  Set before a call to C<getconf>, or
read afterwards to see if a config file was used.  New in
Scriptalicious 1.16

=item B<getopt(@getopt_args)>

Fetch arguments via C<Getopt::Long::GetOptions>.  The C<bundling>
option is enabled by default - which differs from the standard
configuration of B<Getopt::Long>.  To alter the configuration, simply
call C<Getopt::Long::config>.  See L<Getopt::Long> for more
information.

=item B<getopt_lenient(@getopt_args)>

Just like C<getopt()>, but doesn't cause a fatal error if there are
any unknown options.

=item B<getconf(@getopt_args)>

Fetches configuration, takes arguments in the same form as
B<getopt()>..

The configuration file is expected to be in F<~/.PROGNAMErc>,
F</etc/perl/PROGNAME.conf>, or F</etc/PROGNAME.conf>.  Only the first
found file is read, and unknown options are ignored for the time
being.

The file is expected to be in YAML format, with the top entity being a
hash, and the keys of the hash being the same as specifying options on
the command line.  Using YAML as a format allows some simplificiations
to getopt-style processing - C<=s%> and C<=s@> style options are
expected to be in a real hash or list format in the config file, and
boolean options must be set to C<true> or C<false> (or some common
equivalents).

Returns the configuration file as Load()'ed by YAML in scalar context,
or the argument list it was passed in list context.

For example, this minimal script (missing the documentation, but hey
at least it's a start);

  getopt getconf
      ( "something|s" => \$foo,
        "invertable|I!" => \$invertable,
        "integer|i=i" => \$bar,
        "string|s=s" => \$cheese,
        "list|l=s@" => \@list,
        "hash|H=s%" => \%hash, );

Will accept the following invocation styles;

  foo.pl --help
  foo.pl --version
  foo.pl --verbose
  foo.pl --debug
  foo.pl --quiet
  
  foo.pl --something
  foo.pl --invertable
  foo.pl --no-invertable    <=== FORM DIFFERS IN CONFIG FILE
  foo.pl --integer=7
  foo.pl --string=anything
  foo.pl --list one --list two --list three
  foo.pl --hash foo=bar --hash baz=cheese

Equivalent config files:

  something: 1

  invertable: on

  invertable: off

  integer: 7

  string: anything

  list:
    - one
    - two
    - three

  list: [ one, two, three ]

  hash:
    foo: bar
    baz: cheese

Note that more complex and possibly arcane usages of Getopt::Long
features may not work with getconf (patches welcome).

This can be handy for things like database connection strings; all you
have to do is make an option for them, and then the user of the
script, or a SysAdmin can set up their own config file for the script
to automatically set the options.

=item B<getconf_f($filename, @getopt_args)>

As B<getconf()>, but specify a filename.

=cut

=item B<say "something">

Prints a message to standard output, unless quiet mode (C<-q> or
C<--quiet>) was specified.  For normal program messages.

=item B<mutter "progress">

Prints a message to standard output, if verbose mode (C<-v>) or debug
mode (C<-d>) is enabled (ie, if C<$VERBOSE E<gt> 0>).  For messages
designed to help a I<user of the script> to see more information about
what is going on.

=item B<whisper "detail">

Prints a message to standard output, if debug mode (C<-d>) is enabled
or multiple verbose options were passed (ie, if C<$VERBOSE E<gt> 1>).
For messages designed to help a I<person debugging the script> to see
more information about what is going on internally to the script.

=item B<abort "won't go to sea in a storm">

Prints a short program usage message (extracted from the POD synopsis)
and exits with an error code.

=item B<moan "weather is miserable">

Prints a warning to standard error.  It is preceded with the text
C<warning:>.  The program does not exit.

=item B<protest "don't know the weather report">

Prints an error message to standard error.  It is preceded with the
text C<error:>.  The program does not exit.

=item B<barf "hit an iceberg">

Prints a warning to standard error.  It is preceded with the text
C<warning:>.  The program does not exit.

=item B<run("command", "arg1", "arg2")>

Runs a command or closure, barf's with a relevant error message if
there is a problem.  Program output is suppressed unless running in
verbose mode.

C<run()> and the three alternatives listed below may perform arbitrary
filehandle redirection before executing the command.  This can be a
very convenient way to do shell-like filehandle plumbing.

For example;

  run( -in => sub { print "Hello, world!\n" },
       -out => "/tmp/outfile",
       -out2 => "/dev/null",
       @command );

This will connect the child process' standard input (C<-in>) to a
closure that is printing "C<Hello, world!\n>".  The output from the
closure will appear on standard input of the run command.  Note that
the closure is run in a sub-process and so will not be able to set
variables in the calling program.

It will also connect the program's standard output (C<-out>) to
C</tmp/outfile>, and its standard error (filehandle 2) to C</dev/null>
(the traditional way of junking error output).

If you wanted to connect two filehandles to the same place, you could
pass in C<GLOB> references instead;

  run( -out => \*MYOUT,
       -out2 => \*MYOUT,
       @command );

Any filehandle can be opened in any mode; C<-in> merely defaults to
meaning C<-in0>, and C<-out> defaults to meaning C<-out1>.  There is
no C<-err>; use C<-out2>.  C<-rw> exists (defaulting to C<-rw0>), but
is probably of limited use.

Here is an example of using C<prompt_passwd()> to hijack C<gpg>'s
password grabbing;

  my $password = prompt_passwd("Encryption password: ");
  my $encrypted = run( -in4 => sub { print "$password\n" },
                       "gpg", "--passphrase-fd", "4", "-c", $file )

=item B<run_err("command", "arg2", "arg1")>

Same as run, but returns the error code rather than assuming that the
command will successfully complete.  Again, output it suppressed.

=item B<capture("command", "1gra", "2gra")>

runs a command, capturing its output, barfs if there is a problem.
Returns the output of the command as a list or a scalar.

=item B<capture_err("command", "foo")>

Works as B<capture>, but the first returned item is the error code of
the command ($?) rather than the first line of its output.  Also, it
only ever returns the output as a list.

Usage:

   my ($rc, @output) = capture_err("somecommand", @args);

=item B<hush_exec()>

=item B<unhush_exec()>

C<hush_exec> is used to indicate that the programs you are running are
only of interest to someone debugging the script.  So, the messages
showing commands run and giving execution timings will not be printed
without C<-vv> (double verbose) or C<-d> (debug, which is the same
thing).

=item B<start_timer()>

=item B<show_delta()>

=item B<show_elapsed()>

These three little functions are for printing run times in your
scripts.  Times are displayed for running external programs with
verbose mode normally, but this will let you display running times for
your main program easily.

=item B<sci_unit($num, [$unit, $precision])>

Returns a number, scaled using normal scientific prefixes (from atto
to exa).  Optionally specify a precision which is passed to sprintf()
(see L<perldoc/sprintf>).  The default is three significant figures.

From Scriptalicious 1.08, the "u" character is used in place of the
Greek "mu" due to encoding compatibility issues.

=item B<time_unit($num, [$precision])>

Converts a floating point number of seconds to a human-readable time,
the precision specifies the number of significant decimal digits,
which is used to compute a "quanta" for the value given, values below
which are not displayed.  $precision defaults to 4.

examples:

 time_unit(10.1) => "10.10s"
 time_unit(1) => "1.000s"
 time_unit(0.1) => "100ms"
 time_unit(86401,2) => "1d 0h"
 time_unit(86401,3) => "1d 0h"
 time_unit(86401) => "1d 0h:0m"
 time_unit(86400+3600/2) => "1d 0h:30m"
 time_unit(86401,5) => "1d 0h:0m:1s"
 time_unit(7*86400) => "1w0d 0h"

=item B<prompt_regex($prompt, qr/(.*)/)>

Prompts for something, using the prompt "C<$prompt>", matching the
entered value (sans trailing linefeed) against the passed regex.

Note that this differs from the previous behaviour of prompt_regex,
which took a sub.

=item B<prompt_sub($prompt, sub { /(.*)/ && $1 })>

Prompts for something, using the prompt "C<$prompt>", feeding the sub
with the entered value (sans trailing linefeed), to use a default, the
passed sub should simply return it with empty input.

=item B<prompt_passwd([$prompt])>

Same as C<prompt_regex>, but turns off echo.  C<$prompt> defaults to
"C<Password: >" for this function.

=item B<prompt_string([$prompt])>

Prompt for a string.

=item B<prompt_int([$prompt])>

get an integer

=item B<prompt_for([ [$type =>] $what])>

Prompts for a value for C<$what>.  This constructs a prompt saying, eg
"C<Enter value for $what>".  Calls the equivalent C<prompt_foo()>
method.

=item B<prompt_yn([$prompt])>

prompts for yes or no, presuming neither

=item B<prompt_Yn([$prompt])>

=item B<prompt_yN([$prompt])>

prompts for yes or no, presuming yes and no, respectively.

You can also spell these as C<prompt_nY> and C<prompt_Ny>.

=item B<anydump($ref)>

Dump C<$ref> via C<YAML>, falling back to C<Data::Dumper> if YAML
fails to load (or dies during the dump).  Returns a string.

=item B<tsay($template, $vars)>

Prints the template C<$template> with C<$vars>.  C<$template> may be
included at the end of the file as a data section, for instance:

 use Scriptalicious;

 tsay hello => { name => "Bernie" };

 __END__

 __hello__
 Hello, [% name %]
 [% INCLUDE yomomma %]
 __yomomma__
 Yo momma's so fat your family portrait has stretchmarks.

This will print:

 Hello, Bernie
 Yo momma's so fat your family portrait has stretchmarks.

Note that the script goes to lengths to make sure that the information
is always printed whether or not Template Toolkit is installed.  This
gets pretty verbose, but at least solves the "argh!  that script
failed, but I don't know why because it needed this huge dependency to
tell me" problem.

For example, the above would be printed as:

 scriptname: 

=item B<foo()>

If you've got a short little Perl function that implements something
useful for people writing Shell scripts in Perl, then please feel free
to contribute it.  And if it really is scriptalicious, you can bet
your momma on it getting into this module!

=back

=head1 SEE ALSO

Simon Cozen's L<Getopt::Auto> module does a very similar thing to this
module, in a quite different way.  However, it is missing C<say>,
C<run>, etc.  So you'll need to use some other module for those.  But
it does have some other features you might like and is probably
engineered better.

There's a template script at L<Getopt::Long/Documentation and help
texts> that contains a script template that demonstrates what is
necessary to get the basic man page / usage things working with the
traditional L<Getopt::Long> and L<Pod::Usage> combination.

L<Getopt::Plus> is a swiss army chainsaw of Getopt::* style modules,
contrasting to this module's approach of elegant simplicity (quiet in
the cheap seats!).

L<Getopt::EUCLID> is Damian Conway's take on this.

Finally, if you don't mind the dependencies of Moose (or Mouse), then
L<MooseX::Getopt> and L<MooseX::SimpleConfig> are much more elegant
approaches to getopt handling and configuration than this module.

If you have solved this problem in a new and interesting way, or even
rehashed it in an old, boring and inelegant way and want your module
to be listed here, please contact the

=head1 AUTHOR AND LICENSE

Sam Vilain, L<samv@cpan.org>

Copyright 2005-2008, Sam Vilain.  All rights reserved.  This program
is free software; you can use it and/or distribute it under the same
terms as Perl itself; either the latest stable release of Perl when
the module was written, or any subsequent stable release.

Please note that this applies retrospectively to all Scriptalicious
releases; apologies for the lack of an explicit license.

=cut