Scriptalicious(3) Make scripts more delicious to SysAdmins

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

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 "-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 $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 "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 "--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 "barf", then it is considered to be a hard run-time failure, and the invitation to read the "--help" page to get usage not given. Also, the messages are much tidier than you get with "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 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:

$VERBOSE
Set to 0 by default, and 1 if "-v" or "--verbose" was found during the call to "getopt()". Extra "-v"'s or "--debug" will push this variable higher. If "-q" or "--quiet" is specified, this will be less than one.
$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.
$CONFIG
Name of the configuration file. Set before a call to "getconf", or read afterwards to see if a config file was used. New in Scriptalicious 1.16
getopt(@getopt_args)
Fetch arguments via "Getopt::Long::GetOptions". The "bundling" option is enabled by default - which differs from the standard configuration of Getopt::Long. To alter the configuration, simply call "Getopt::Long::config". See Getopt::Long for more information.
getopt_lenient(@getopt_args)
Just like "getopt()", but doesn't cause a fatal error if there are any unknown options.
getconf(@getopt_args)
Fetches configuration, takes arguments in the same form as getopt()..

The configuration file is expected to be in ~/.PROGNAMErc, /etc/perl/PROGNAME.conf, or /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 - "=s%" and "[email protected]" style options are expected to be in a real hash or list format in the config file, and boolean options must be set to "true" or "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|[email protected]" => \@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.

getconf_f($filename, @getopt_args)
As getconf(), but specify a filename.
say "something"
Prints a message to standard output, unless quiet mode ("-q" or "--quiet") was specified. For normal program messages.
mutter "progress"
Prints a message to standard output, if verbose mode ("-v") or debug mode ("-d") is enabled (ie, if "$VERBOSE > 0"). For messages designed to help a user of the script to see more information about what is going on.
whisper "detail"
Prints a message to standard output, if debug mode ("-d") is enabled or multiple verbose options were passed (ie, if "$VERBOSE > 1"). For messages designed to help a person debugging the script to see more information about what is going on internally to the script.
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.
moan "weather is miserable"
Prints a warning to standard error. It is preceded with the text "warning:". The program does not exit.
protest "don't know the weather report"
Prints an error message to standard error. It is preceded with the text "error:". The program does not exit.
barf "hit an iceberg"
Prints a warning to standard error. It is preceded with the text "warning:". The program does not exit.
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.

"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 ("-in") to a closure that is printing ""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 ("-out") to "/tmp/outfile", and its standard error (filehandle 2) to "/dev/null" (the traditional way of junking error output).

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

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

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

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

  my $password = prompt_passwd("Encryption password: ");
  my $encrypted = run( -in4 => sub { print "$password\n" },
                       "gpg", "--passphrase-fd", "4", "-c", $file )
run_err("command", "arg2", "arg1")
Same as run, but returns the error code rather than assuming that the command will successfully complete. Again, output it suppressed.
capture("command", "1gra", "2gra")
runs a command, capturing its output, barfs if there is a problem. Returns the output of the command as a list or a scalar.
capture_err("command", "foo")
Works as capture, but the first returned item is the error code of the command ($?) rather than the first line of its output. Also, it only ever returns the output as a list.

Usage:

   my ($rc, @output) = capture_err("somecommand", @args);
hush_exec()
unhush_exec()
"hush_exec" is used to indicate that the programs you are running are only of interest to someone debugging the script. So, the messages showing commands run and giving execution timings will not be printed without "-vv" (double verbose) or "-d" (debug, which is the same thing).
start_timer()
show_delta()
show_elapsed()
These three little functions are for printing run times in your scripts. Times are displayed for running external programs with verbose mode normally, but this will let you display running times for your main program easily.
sci_unit($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 ``sprintf'' in perldoc). 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.

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"
 time_unit(-0.0002) => "-200us"
prompt_regex($prompt, qr/(.*)/)
Prompts for something, using the prompt "$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.

prompt_sub($prompt, sub { /(.*)/ && $1 })
Prompts for something, using the prompt "$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.
prompt_passwd([$prompt])
Same as "prompt_regex", but turns off echo. $prompt defaults to ""Password: "" for this function.
prompt_string([$prompt])
Prompt for a string.
prompt_int([$prompt])
get an integer
prompt_for([ [$type =] $what])>
Prompts for a value for $what. This constructs a prompt saying, eg ""Enter value for $what"". Calls the equivalent "prompt_foo()" method.
prompt_yn([$prompt])
prompts for yes or no, presuming neither
prompt_Yn([$prompt])
prompt_yN([$prompt])
prompts for yes or no, presuming yes and no, respectively.

You can also spell these as "prompt_nY" and "prompt_Ny".

anydump($ref)
Dump $ref via "YAML", falling back to "Data::Dumper" if YAML fails to load (or dies during the dump). Returns a string.
tsay($template, $vars)
Prints the template $template with $vars. $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:
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!

AUTHOR AND LICENSE

Sam Vilain, [email protected]

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.