1Pod::Usage(3) User Contributed Perl Documentation Pod::Usage(3)
2
6 Pod::Usage, pod2usage() - print a usage message from embedded pod
7 documentation
8
10 use Pod::Usage
11 my $message_text = "This text precedes the usage message.";
13 my $exit_status = 2; ## The exit status to use
14 my $verbose_level = 0; ## The verbose level to use
15 my $filehandle = \*STDERR; ## The filehandle to write to
16 pod2usage($message_text);
18 pod2usage($exit_status);
20 pod2usage( { -message => $message_text ,
22 -exitval => $exit_status ,
23 -verbose => $verbose_level,
24 -output => $filehandle } );
25 pod2usage( -msg => $message_text ,
27 -exitval => $exit_status ,
28 -verbose => $verbose_level,
29 -output => $filehandle );
30 pod2usage( -verbose => 2,
32 -noperldoc => 1 )
33
35 pod2usage should be given either a single argument, or a list of
36 arguments corresponding to an associative array (a "hash"). When a
37 single argument is given, it should correspond to exactly one of the
38 following:
39 · A string containing the text of a message to print before printing
41 the usage message
42 · A numeric value corresponding to the desired exit status
44 · A reference to a hash
46 If more than one argument is given then the entire argument list is
48 assumed to be a hash. If a hash is supplied (either as a reference or
49 as a list) it should contain one or more elements with the following
50 keys:
51 "-message"
53 "-msg"
54 The text of a message to print immediately prior to printing the
55 program's usage message.
56 "-exitval"
58 The desired exit status to pass to the exit() function. This
59 should be an integer, or else the string "NOEXIT" to indicate that
60 control should simply be returned without terminating the invoking
61 process.
62 "-verbose"
64 The desired level of "verboseness" to use when printing the usage
65 message. If the corresponding value is 0, then only the "SYNOPSIS"
66 section of the pod documentation is printed. If the corresponding
67 value is 1, then the "SYNOPSIS" section, along with any section
68 entitled "OPTIONS", "ARGUMENTS", or "OPTIONS AND ARGUMENTS" is
69 printed. If the corresponding value is 2 or more then the entire
70 manpage is printed.
71 The special verbosity level 99 requires to also specify the
73 -sections parameter; then these sections are extracted and printed.
74 "-sections"
76 A string representing a selection list for sections to be printed
77 when -verbose is set to 99, e.g.
78 "NAME|SYNOPSIS|DESCRIPTION|VERSION".
79 Alternatively, an array reference of section specifications can be
81 used:
82 pod2usage(-verbose => 99,
84 -sections => [ qw(fred fred/subsection) ] );
85 "-output"
87 A reference to a filehandle, or the pathname of a file to which the
88 usage message should be written. The default is "\*STDERR" unless
89 the exit value is less than 2 (in which case the default is
90 "\*STDOUT").
91 "-input"
93 A reference to a filehandle, or the pathname of a file from which
94 the invoking script's pod documentation should be read. It
95 defaults to the file indicated by $0 ($PROGRAM_NAME for users of
96 English.pm).
97 If you are calling pod2usage() from a module and want to display
99 that module's POD, you can use this:
100 use Pod::Find qw(pod_where);
102 pod2usage( -input => pod_where({-inc => 1}, __PACKAGE__) );
103 "-pathlist"
105 A list of directory paths. If the input file does not exist, then
106 it will be searched for in the given directory list (in the order
107 the directories appear in the list). It defaults to the list of
108 directories implied by $ENV{PATH}. The list may be specified either
109 by a reference to an array, or by a string of directory paths which
110 use the same path separator as $ENV{PATH} on your system (e.g., ":"
111 for Unix, ";" for MSWin32 and DOS).
112 "-noperldoc"
114 By default, Pod::Usage will call perldoc when -verbose >= 2 is
115 specified. This does not work well e.g. if the script was packed
116 with PAR. The -noperldoc option suppresses the external call to
117 perldoc and uses the simple text formatter (Pod::Text) to output
118 the POD.
119 Formatting base class
121 The default text formatter is Pod::Text. The base class for Pod::Usage
122 can be defined by pre-setting $Pod::Usage::Formatter before loading
123 Pod::Usage, e.g.:
124 BEGIN { $Pod::Usage::Formatter = 'Pod::Text::Termcap'; }
126 use Pod::Usage qw(pod2usage);
127 Pass-through options
129 The following options are passed through to the underlying text
130 formatter. See the manual pages of these modules for more information.
131 alt code indent loose margin quotes sentence stderr utf8 width
133
135 pod2usage will print a usage message for the invoking script (using its
136 embedded pod documentation) and then exit the script with the desired
137 exit status. The usage message printed may have any one of three levels
138 of "verboseness": If the verbose level is 0, then only a synopsis is
139 printed. If the verbose level is 1, then the synopsis is printed along
140 with a description (if present) of the command line options and
141 arguments. If the verbose level is 2, then the entire manual page is
142 printed.
143 Unless they are explicitly specified, the default values for the exit
145 status, verbose level, and output stream to use are determined as
146 follows:
147 · If neither the exit status nor the verbose level is specified, then
149 the default is to use an exit status of 2 with a verbose level of
150 0.
151 · If an exit status is specified but the verbose level is not, then
153 the verbose level will default to 1 if the exit status is less than
154 2 and will default to 0 otherwise.
155 · If an exit status is not specified but verbose level is given, then
157 the exit status will default to 2 if the verbose level is 0 and
158 will default to 1 otherwise.
159 · If the exit status used is less than 2, then output is printed on
161 "STDOUT". Otherwise output is printed on "STDERR".
162 Although the above may seem a bit confusing at first, it generally does
164 "the right thing" in most situations. This determination of the
165 default values to use is based upon the following typical Unix
166 conventions:
167 · An exit status of 0 implies "success". For example, diff(1) exits
169 with a status of 0 if the two files have the same contents.
170 · An exit status of 1 implies possibly abnormal, but non-defective,
172 program termination. For example, grep(1) exits with a status of 1
173 if it did not find a matching line for the given regular
174 expression.
175 · An exit status of 2 or more implies a fatal error. For example,
177 ls(1) exits with a status of 2 if you specify an illegal (unknown)
178 option on the command line.
179 · Usage messages issued as a result of bad command-line syntax should
181 go to "STDERR". However, usage messages issued due to an explicit
182 request to print usage (like specifying -help on the command line)
183 should go to "STDOUT", just in case the user wants to pipe the
184 output to a pager (such as more(1)).
185 · If program usage has been explicitly requested by the user, it is
187 often desirable to exit with a status of 1 (as opposed to 0) after
188 issuing the user-requested usage message. It is also desirable to
189 give a more verbose description of program usage in this case.
190 pod2usage doesn't force the above conventions upon you, but it will use
192 them by default if you don't expressly tell it to do otherwise. The
193 ability of pod2usage() to accept a single number or a string makes it
194 convenient to use as an innocent looking error message handling
195 function:
196 use Pod::Usage;
198 use Getopt::Long;
199 ## Parse options
201 GetOptions("help", "man", "flag1") || pod2usage(2);
202 pod2usage(1) if ($opt_help);
203 pod2usage(-verbose => 2) if ($opt_man);
204 ## Check for too many filenames
206 pod2usage("$0: Too many files given.\n") if (@ARGV > 1);
207 Some user's however may feel that the above "economy of expression" is
209 not particularly readable nor consistent and may instead choose to do
210 something more like the following:
211 use Pod::Usage;
213 use Getopt::Long;
214 ## Parse options
216 GetOptions("help", "man", "flag1") || pod2usage(-verbose => 0);
217 pod2usage(-verbose => 1) if ($opt_help);
218 pod2usage(-verbose => 2) if ($opt_man);
219 ## Check for too many filenames
221 pod2usage(-verbose => 2, -message => "$0: Too many files given.\n")
222 if (@ARGV > 1);
223 As with all things in Perl, there's more than one way to do it, and
225 pod2usage() adheres to this philosophy. If you are interested in
226 seeing a number of different ways to invoke pod2usage (although by no
227 means exhaustive), please refer to "EXAMPLES".
228
230 Each of the following invocations of "pod2usage()" will print just the
231 "SYNOPSIS" section to "STDERR" and will exit with a status of 2:
232 pod2usage();
234 pod2usage(2);
236 pod2usage(-verbose => 0);
238 pod2usage(-exitval => 2);
240 pod2usage({-exitval => 2, -output => \*STDERR});
242 pod2usage({-verbose => 0, -output => \*STDERR});
244 pod2usage(-exitval => 2, -verbose => 0);
246 pod2usage(-exitval => 2, -verbose => 0, -output => \*STDERR);
248 Each of the following invocations of "pod2usage()" will print a message
250 of "Syntax error." (followed by a newline) to "STDERR", immediately
251 followed by just the "SYNOPSIS" section (also printed to "STDERR") and
252 will exit with a status of 2:
253 pod2usage("Syntax error.");
255 pod2usage(-message => "Syntax error.", -verbose => 0);
257 pod2usage(-msg => "Syntax error.", -exitval => 2);
259 pod2usage({-msg => "Syntax error.", -exitval => 2, -output => \*STDERR});
261 pod2usage({-msg => "Syntax error.", -verbose => 0, -output => \*STDERR});
263 pod2usage(-msg => "Syntax error.", -exitval => 2, -verbose => 0);
265 pod2usage(-message => "Syntax error.",
267 -exitval => 2,
268 -verbose => 0,
269 -output => \*STDERR);
270 Each of the following invocations of "pod2usage()" will print the
272 "SYNOPSIS" section and any "OPTIONS" and/or "ARGUMENTS" sections to
273 "STDOUT" and will exit with a status of 1:
274 pod2usage(1);
276 pod2usage(-verbose => 1);
278 pod2usage(-exitval => 1);
280 pod2usage({-exitval => 1, -output => \*STDOUT});
282 pod2usage({-verbose => 1, -output => \*STDOUT});
284 pod2usage(-exitval => 1, -verbose => 1);
286 pod2usage(-exitval => 1, -verbose => 1, -output => \*STDOUT});
288 Each of the following invocations of "pod2usage()" will print the
290 entire manual page to "STDOUT" and will exit with a status of 1:
291 pod2usage(-verbose => 2);
293 pod2usage({-verbose => 2, -output => \*STDOUT});
295 pod2usage(-exitval => 1, -verbose => 2);
297 pod2usage({-exitval => 1, -verbose => 2, -output => \*STDOUT});
299 Recommended Use
301 Most scripts should print some type of usage message to "STDERR" when a
302 command line syntax error is detected. They should also provide an
303 option (usually "-H" or "-help") to print a (possibly more verbose)
304 usage message to "STDOUT". Some scripts may even wish to go so far as
305 to provide a means of printing their complete documentation to "STDOUT"
306 (perhaps by allowing a "-man" option). The following complete example
307 uses Pod::Usage in combination with Getopt::Long to do all of these
308 things:
309 use Getopt::Long;
311 use Pod::Usage;
312 my $man = 0;
314 my $help = 0;
315 ## Parse options and print usage if there is a syntax error,
316 ## or if usage was explicitly requested.
317 GetOptions('help|?' => \$help, man => \$man) or pod2usage(2);
318 pod2usage(1) if $help;
319 pod2usage(-verbose => 2) if $man;
320 ## If no arguments were given, then allow STDIN to be used only
322 ## if it's not connected to a terminal (otherwise print usage)
323 pod2usage("$0: No files given.") if ((@ARGV == 0) && (-t STDIN));
324 __END__
325 =head1 NAME
327 sample - Using GetOpt::Long and Pod::Usage
329 =head1 SYNOPSIS
331 sample [options] [file ...]
333 Options:
335 -help brief help message
336 -man full documentation
337 =head1 OPTIONS
339 =over 8
341 =item B<-help>
343 Print a brief help message and exits.
345 =item B<-man>
347 Prints the manual page and exits.
349 =back
351 =head1 DESCRIPTION
353 B<This program> will read the given input file(s) and do something
355 useful with the contents thereof.
356 =cut
358
360 By default, pod2usage() will use $0 as the path to the pod input file.
361 Unfortunately, not all systems on which Perl runs will set $0 properly
362 (although if $0 isn't found, pod2usage() will search $ENV{PATH} or else
363 the list specified by the "-pathlist" option). If this is the case for
364 your system, you may need to explicitly specify the path to the pod
365 docs for the invoking script using something similar to the following:
366 pod2usage(-exitval => 2, -input => "/path/to/your/pod/docs");
368 In the pathological case that a script is called via a relative path
370 and the script itself changes the current working directory (see
371 "chdir" in perlfunc) before calling pod2usage, Pod::Usage will fail
372 even on robust platforms. Don't do that. Or use FindBin to locate the
373 script:
374 use FindBin;
376 pod2usage(-input => $FindBin::Bin . "/" . $FindBin::Script);
377
379 Please report bugs using <http://rt.cpan.org>.
380 Marek Rouchal <marekr@cpan.org>
382 Brad Appleton <bradapp@enteract.com>
384 Based on code for Pod::Text::pod2text() written by Tom Christiansen
386 <tchrist@mox.perl.com>
387
389 rjbs for refactoring Pod::Usage to not use Pod::Parser any more.
390 Steven McDougall <swmcd@world.std.com> for his help and patience with
392 re-writing this manpage.
393
395 Pod::Usage is now a standalone distribution, depending on Pod::Text
396 which in turn depends on Pod::Simple.
397 Pod::Perldoc, Getopt::Long, Pod::Find, FindBin, Pod::Text,
399 Pod::Text::Termcap, Pod::Simple
400perl v5.16.3 2013-06-02 Pod::Usage(3)