1Net::Remctl::Backend(3)User Contributed Perl DocumentatioNnet::Remctl::Backend(3)
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NAME

6       Net::Remctl::Backend - Helper infrastructure for remctl backend
7       programs
8

SYNOPSIS

10           use Net::Remctl::Backend;
11
12           my %commands = (
13               cmd1 => { code => \&run_cmd1 },
14               cmd2 => { code => \&run_cmd2 },
15           );
16           my $backend = Net::Remctl::Backend->new({
17               commands => \%commands,
18           });
19           exit $backend->run();
20

DESCRIPTION

22       Net::Remctl::Backend provides a framework for remctl backend commands
23       (commands run by remctld).  It can be configured with a list of
24       supported subcommands and handles all the command-line parsing and
25       syntax checking, dispatching the command to the appropriate sub if it
26       is valid.
27

CLASS METHODS

29       new(CONFIG)
30           Create a new backend object with the given configuration.  CONFIG
31           should be an anonymous hash with one or more of the following keys:
32
33           command
34               If set, defines the base remctl command implemented by this
35               backend.  The primary use of this string is in usage and help
36               output.  If set, it will be added to the beginning of each
37               command syntax description so that the help output will match
38               the remctl command that the user actually runs.
39
40           commands
41               The value of this key should be an anonymous hash describing
42               all of the commands that are supported.  See below for the
43               supported keys in the command configuration.
44
45           help_banner
46               If set, the value will be displayed as the first line of help
47               output.  Recommended best practice is to use a string of the
48               form:
49
50                   <service> remctl help:
51
52               where <service> is something like "Event handling" or "User
53               database" or whatever this set of commands generally does or
54               manipulates.
55
56           The commands key, described above, takes a hash of properties for
57           each subcommand supported by this backend.  The possible keys in
58           that hash are:
59
60           args_match
61               A reference to an array of regexes that must match the
62               arguments to this function.  Each element of the array is
63               matched against the corresponding element in the array of
64               arguments, and if the corresponding regular expression does not
65               match, the command will be rejected with an error about an
66               invalid argument.  Set the regular expression to undef to not
67               check the corresponding argument.
68
69               There is currently no way to check all arguments in commands
70               that take any number of arguments.
71
72           args_max
73               The maximum number of arguments.  If there are more than this
74               number of arguments, run() will die with an error message
75               without running the command.
76
77           args_min
78               The minimum number of arguments.  If there are fewer than this
79               number of arguments, run() will die with an error message
80               without running the command.
81
82           code
83               A reference to the sub that implements this command.  This sub
84               will be called with the arguments passed on the command line as
85               its arguments (possibly preceded by the options hash if the
86               "options" parameter is set as described below).  It should
87               return the exit status that should be used by the backend as a
88               whole: 0 for success and some non-zero value for an error
89               condition.  This sub should print to STDOUT and STDERR to
90               communicate back to the remctl client.
91
92           nested
93               If set, indicates that this is a nested command.  The value
94               should be a nested hash of command definitions, the same as the
95               parameter to the "commands" argument to new().  When this is
96               set, the first argument to this command is taken to be a
97               subcommand name, which is looked up in the hash.  All of the
98               hash parameters are interpreted the same as if it were a top-
99               level command.
100
101               If this command is called without any arguments, behavior
102               varies based on whether the "code" parameter is also set
103               alongside the "nested" parameter.  If "code" is set, the
104               command is called normally, with no arguments.  If "code" is
105               not set, calling this command without a subcommand is treated
106               as an unknown command.
107
108           options
109               A reference to an array of Getopt::Long option specifications.
110               If this setting is present, the arguments passed to run() will
111               be parsed by Getopt::Long using this option specification
112               first, before any other option processing (including checking
113               for minimum and maximum numbers of arguments, checking the
114               validity of arguments, or replacing arguments with data from
115               standard input).  The result of parsing options will be passed,
116               as a reference to a hash, as the first argument to the code
117               that implements this command, with all remaining arguments
118               passed as the subsequent arguments.
119
120               For example, if this is set to "['help|h', 'version|v']" and
121               the arguments passed to run() are:
122
123                   command -hv foo bar
124
125               then the code implementing "command" will be called with the
126               following arguments:
127
128                   { help => 1, version => 1 }, 'foo', 'bar'
129
130               Getopt::Long will always be configured with the options
131               "bundling", "no_ignore_case", and "require_order".  This means,
132               among other things, that the first non-option argument will
133               stop option parsing and all remaining arguments will be passed
134               through verbatim.
135
136               If Getopt::Long rejects the options (due to an unknown option
137               or an invalid argument to an option, for example), run() will
138               die with the error message from Getopt::Long without running
139               the command.
140
141           stdin
142               Specifies that one argument to this function should be read
143               from standard input.  All of the data on standard input until
144               end of file will be read into memory, and that data will become
145               the argument number given by the value of this key is the
146               argument (based at 1).  So if this property is set to 1, the
147               first argument will be the data from standard input, and any
148               other arguments will be shifted down accordingly.  The value
149               may be -1, in which case the data from standard input will
150               become the last argument, no matter how many arguments there
151               currently are.
152
153               Checks for the number of arguments and for the validity of
154               arguments with regular expression verification are done after
155               reading the data from standard input and transforming the
156               argument list accordingly.
157
158           summary
159               The summary of what this subcommand does, as text.  Ideally,
160               this should fit on the same line with the syntax after the help
161               output has been laid out in columns.  If it is too long to fit,
162               it will be wrapped, with each subsequent line indented to the
163               column where the summaries start.
164
165               If this key is omitted, the subcommand will still be shown in
166               help output, provided that it has a syntax key, but without any
167               trailing summary.
168
169           syntax
170               The syntax of this subcommand.  This should be short, since it
171               needs to fit on the same line as the summary of what this
172               subcommand does.  Both the command and subcommand should be
173               omitted; the former will be set by the command parameter to the
174               new() constructor for Net::Remctl::Backend, and the latter will
175               come from the command itself.  A typical example will look
176               like:
177
178                   syntax => '<object>'
179
180               which will result in help output (assuming command is set to
181               "object" and this parameter is set on the "delete" command)
182               that looks like:
183
184                   object delete <object>
185
186               Use abbreviations heavily to keep this string short so that the
187               help output will remain readable.
188
189               Set this key to the empty string to indicate that this
190               subcommand takes no arguments or flags.
191
192               If this key is omitted, the subcommand will be omitted from
193               help output.
194

INSTANCE METHODS

196       help()
197           Returns the formatted help summary for the commands supported by
198           this backend.  This is the same as would be printed to standard
199           output in response to the command "help" with no arguments.  The
200           output will consist of the syntax and summary attributes for each
201           command that has a syntax attribute defined, as described above
202           under the command specification.  It will be wrapped to 80 columns.
203
204       run([COMMAND[, ARG ...]])
205           Parse the command line and perform the appropriate action.  The
206           return value will be the return value of the command run (if any),
207           which should be the exit status that the backend script should use.
208
209           The command (which is the remctl subcommand) and arguments can be
210           passed directly to run() as parameters.  If no arguments are
211           passed, run() expects @ARGV to contain the parameters passed to the
212           backend script.  Either way the first argument will be the
213           subcommand, used to find the appropriate command to run, and any
214           remaining arguments will be arguments to that command.  (Note that
215           if the "options" parameter is set, the first argument passed to the
216           underlying command will be the options hash.)
217
218           If there are errors in the parameters to the command, run() will
219           die with an appropriate error message.
220

DIAGNOSTICS

222       Since Net::Remctl::Backend is designed to handle command line parsing
223       for a script and report appropriate errors if there are problems with
224       the argument, its run() method may die with various errors.  The
225       possible errors are listed below.  All will be terminated with a
226       newline so the Perl context information won't be appended.
227
228       %s: insufficient arguments
229           The given command was configured with a "args_min" parameter, and
230           the user passed in fewer arguments than that.
231
232       %s: invalid argument: %s
233           The given argument to the given command failed to match a regular
234           expression that was set with an "args_match" parameter.
235
236       %s: too many arguments
237           The given command was configured with a "args_max" parameter, and
238           the user passed in more arguments than that.
239

COMPATIBILITY

241       This module was added in the 3.4 release of remctl.  Since 3.5, the
242       module version matches the remctl version but with a leading zero added
243       so that the minor version always has two numbers (so
244       Net::Remctl::Backend 3.05 was included in remctl 3.5).
245
246       All currently-supported methods and options have been supported since
247       the original release of the module.
248

BUGS

250       There is no way to check all arguments with a regex when the command
251       supports any number of arguments.
252

AUTHOR

254       Russ Allbery <eagle@eyrie.org>
255
257       Copyright 2019-2020, 2022 Russ Allbery <eagle@eyrie.org>
258
259       Copyright 2012-2014 The Board of Trustees of the Leland Stanford Junior
260       University
261
262       Permission is hereby granted, free of charge, to any person obtaining a
263       copy of this software and associated documentation files (the
264       "Software"), to deal in the Software without restriction, including
265       without limitation the rights to use, copy, modify, merge, publish,
266       distribute, sublicense, and/or sell copies of the Software, and to
267       permit persons to whom the Software is furnished to do so, subject to
268       the following conditions:
269
270       The above copyright notice and this permission notice shall be included
271       in all copies or substantial portions of the Software.
272
273       THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
274       OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
275       MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
276       IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
277       CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
278       TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
279       SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
280

SEE ALSO

282       remctld(8)
283
284       The current version of this module is available from its web page at
285       <https://www.eyrie.org/~eagle/software/remctl/>.
286
287
288
289perl v5.36.0                      2022-07-23           Net::Remctl::Backend(3)
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