Ubuntu Manpage: Net::Remctl::Backend - Helper infrastructure for remctl backend programs

Provided by: libnet-remctl-perl_3.10-1ubuntu1_amd64

NAME

       Net::Remctl::Backend - Helper infrastructure for remctl backend programs

SYNOPSIS

           use Net::Remctl::Backend;

           my %commands = (
               cmd1 => { code => \&run_cmd1 },
               cmd2 => { code => \&run_cmd2 },
           );
           my $backend = Net::Remctl::Backend->new({
               commands => \%commands,
           });
           exit $backend->run();

DESCRIPTION

       Net::Remctl::Backend provides a framework for remctl backend commands (commands run by
       remctld).  It can be configured with a list of supported subcommands and handles all the
       command-line parsing and syntax checking, dispatching the command to the appropriate sub
       if it is valid.

CLASS METHODS

new(CONFIG)
Create a new backend object with the given configuration. CONFIG should be an
anonymous hash with one or more of the following keys:

command
If set, defines the base remctl command implemented by this backend. The primary
use of this string is in usage and help output. If set, it will be added to the
beginning of each command syntax description so that the help output will match
the remctl command that the user actually runs.

commands
The value of this key should be an anonymous hash describing all of the commands
that are supported. See below for the supported keys in the command
configuration.

help_banner
If set, the value will be displayed as the first line of help output. Recommended
best practice is to use a string of the form:

<service> remctl help:

where <service> is something like "Event handling" or "User database" or whatever
this set of commands generally does or manipulates.

The commands key, described above, takes a hash of properties for each subcommand
supported by this backend. The possible keys in that hash are:

args_match
A reference to an array of regexes that must match the arguments to this function.
Each element of the array is matched against the corresponding element in the
array of arguments, and if the corresponding regular expression does not match,
the command will be rejected with an error about an invalid argument. Set the
regular expression to undef to not check the corresponding argument.

There is currently no way to check all arguments in commands that take any number
of arguments.

args_max
The maximum number of arguments. If there are more than this number of arguments,
run() will die with an error message without running the command.

args_min
The minimum number of arguments. If there are fewer than this number of
arguments, run() will die with an error message without running the command.

code
A reference to the sub that implements this command. This sub will be called with
the arguments passed on the command line as its arguments (possibly preceded by
the options hash if the "options" parameter is set as described below). It should
return the exit status that should be used by the backend as a whole: 0 for
success and some non-zero value for an error condition. This sub should print to
STDOUT and STDERR to communicate back to the remctl client.

nested
If set, indicates that this is a nested command. The value should be a nested
hash of command definitions, the same as the parameter to the "commands" argument
to new(). When this is set, the first argument to this command is taken to be a
subcommand name, which is looked up in the hash. All of the hash parameters are
interpreted the same as if it were a top-level command.

If this command is called without any arguments, behavior varies based on whether
the "code" parameter is also set alongside the "nested" parameter. If "code" is
set, the command is called normally, with no arguments. If "code" is not set,
calling this command without a subcommand is treated as an unknown command.

options
A reference to an array of Getopt::Long option specifications. If this setting is
present, the arguments passed to run() will be parsed by Getopt::Long using this
option specification first, before any other option processing (including checking
for minimum and maximum numbers of arguments, checking the validity of arguments,
or replacing arguments with data from standard input). The result of parsing
options will be passed, as a reference to a hash, as the first argument to the
code that implements this command, with all remaining arguments passed as the
subsequent arguments.

For example, if this is set to "['help|h', 'version|v']" and the arguments passed
to run() are:

command -hv foo bar

then the code implementing "command" will be called with the following arguments:

{ help => 1, version => 1 }, 'foo', 'bar'

Getopt::Long will always be configured with the options "bundling",
"no_ignore_case", and "require_order". This means, among other things, that the
first non-option argument will stop option parsing and all remaining arguments
will be passed through verbatim.

If Getopt::Long rejects the options (due to an unknown option or an invalid
argument to an option, for example), run() will die with the error message from
Getopt::Long without running the command.

stdin
Specifies that one argument to this function should be read from standard input.
All of the data on standard input until end of file will be read into memory, and
that data will become the argument number given by the value of this key is the
argument (based at 1). So if this property is set to 1, the first argument will
be the data from standard input, and any other arguments will be shifted down
accordingly. The value may be -1, in which case the data from standard input will
become the last argument, no matter how many arguments there currently are.

Checks for the number of arguments and for the validity of arguments with regular
expression verification are done after reading the data from standard input and
transforming the argument list accordingly.

summary
The summary of what this subcommand does, as text. Ideally, this should fit on
the same line with the syntax after the help output has been laid out in columns.
If it is too long to fit, it will be wrapped, with each subsequent line indented
to the column where the summaries start.

If this key is omitted, the subcommand will still be shown in help output,
provided that it has a syntax key, but without any trailing summary.

syntax
The syntax of this subcommand. This should be short, since it needs to fit on the
same line as the summary of what this subcommand does. Both the command and
subcommand should be omitted; the former will be set by the command parameter to
the new() constructor for Net::Remctl::Backend, and the latter will come from the
command itself. A typical example will look like:

syntax => '<object>'

which will result in help output (assuming command is set to "object" and this
parameter is set on the "delete" command) that looks like:

object delete <object>

Use abbreviations heavily to keep this string short so that the help output will
remain readable.

Set this key to the empty string to indicate that this subcommand takes no
arguments or flags.

If this key is omitted, the subcommand will be omitted from help output.

INSTANCE METHODS

       help()
           Returns the formatted help summary for the commands supported by this backend.  This
           is the same as would be printed to standard output in response to the command "help"
           with no arguments.  The output will consist of the syntax and summary attributes for
           each command that has a syntax attribute defined, as described above under the command
           specification.  It will be wrapped to 80 columns.

       run([COMMAND[, ARG ...]])
           Parse the command line and perform the appropriate action.  The return value will be
           the return value of the command run (if any), which should be the exit status that the
           backend script should use.

           The command (which is the remctl subcommand) and arguments can be passed directly to
           run() as parameters.  If no arguments are passed, run() expects @ARGV to contain the
           parameters passed to the backend script.  Either way the first argument will be the
           subcommand, used to find the appropriate command to run, and any remaining arguments
           will be arguments to that command.  (Note that if the "options" parameter is set, the
           first argument passed to the underlying command will be the options hash.)

           If there are errors in the parameters to the command, run() will die with an
           appropriate error message.

DIAGNOSTICS

       Since Net::Remctl::Backend is designed to handle command line parsing for a script and
       report appropriate errors if there are problems with the argument, its run() method may
       die with various errors.  The possible errors are listed below.  All will be terminated
       with a newline so the Perl context information won't be appended.

       %s: insufficient arguments
           The given command was configured with a "args_min" parameter, and the user passed in
           fewer arguments than that.

       %s: invalid argument: %s
           The given argument to the given command failed to match a regular expression that was
           set with an "args_match" parameter.

       %s: too many arguments
           The given command was configured with a "args_max" parameter, and the user passed in
           more arguments than that.

COMPATIBILITY

       This module was added in the 3.4 release of remctl.  Since 3.5, the module version matches
       the remctl version but with a leading zero added so that the minor version always has two
       numbers (so Net::Remctl::Backend 3.05 was included in remctl 3.5).

       All currently-supported methods and options have been supported since the original release
       of the module.

BUGS

       There is no way to check all arguments with a regex when the command supports any number
       of arguments.

AUTHOR

       Russ Allbery <eagle@eyrie.org>

COPYRIGHT AND LICENSE

       Copyright 2012, 2013, 2014 The Board of Trustees of the Leland Stanford Junior University

       Permission is hereby granted, free of charge, to any person obtaining a copy of this
       software and associated documentation files (the "Software"), to deal in the Software
       without restriction, including without limitation the rights to use, copy, modify, merge,
       publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
       to whom the Software is furnished to do so, subject to the following conditions:

       The above copyright notice and this permission notice shall be included in all copies or
       substantial portions of the Software.

       THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
       INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
       PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
       FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
       OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
       DEALINGS IN THE SOFTWARE.