1Config::Std(3)        User Contributed Perl Documentation       Config::Std(3)
2
3
4

NAME

6       Config::Std - Load and save configuration files in a standard format
7

VERSION

9       This document describes Config::Std version 0.903
10

SYNOPSIS

12           use Config::Std;
13
14           # Load named config file into specified hash...
15           read_config 'demo2.cfg' => my %config;
16
17           # Extract the value of a key/value pair from a specified section...
18           $config_value = $config{Section_label}{key};
19
20           # Change (or create) the value of a key/value pair...
21           $config{Other_section_label}{other_key} = $new_val;
22
23           # Update the config file from which this hash was loaded...
24           write_config %config;
25
26           # Write the config information to another file as well...
27           write_config %config, $other_file_name;
28

DESCRIPTION

30       This module implements yet another damn configuration-file system.
31
32       The configuration language is deliberately simple and limited, and the
33       module works hard to preserve as much information (section order,
34       comments, etc.) as possible when a configuration file is updated.
35
36       The whole point of Config::Std is to encourage use of one standard
37       layout and syntax in config files. Damian says "I could have gotten
38       away with it, I would have only allowed one separator. But it proved
39       impossible to choose between ":" and "=" (half the people I asked
40       wanted one, half wanted the other)."  Providing round-trip file re-
41       write is the spoonful of sugar to help the medicine go down.  The
42       supported syntax is within the general INI file family
43
44       See Chapter 19 of "Perl Best Practices" (O'Reilly, 2005) for more
45       detail on the rationale for this approach.
46
47   Configuration language
48       The configuration language is a slight extension of the Windows INI
49       format.
50
51       Comments
52
53       A comment starts with a "#" character (Perl-style) or a ";" character
54       (INI-style), and runs to the end of the same line:
55
56           # This is a comment
57
58           ; Ywis, eke hight thilke
59
60       Comments can be placed almost anywhere in a configuration file, except
61       inside a section label, or in the key or value of a configuration
62       variable:
63
64           # Valid comment
65           [ # Not a comment, just a weird section label ]
66
67           ; Valid comment
68           key: value  ; Not a comment, just part of the value
69
70       NOTE BENE -- that last is a BAD EXAMPLE of what is NOT supported.  This
71       module supports full-line comments only, not on same line with semantic
72       content.
73
74       Sections
75
76       A configuration file consists of one or more sections, each of which is
77       introduced by a label in square brackets:
78
79           [SECTION1]        # Almost anything is a valid section label
80
81           [SECTION 2]       # Internal whitespace is allowed (except newlines)
82
83           [%^$%^&!!!]       # The label doesn't have to be alphanumeric
84
85           [ETC. ETC. AS MANY AS YOU WANT]
86
87       The only restriction on section labels is that they must be by
88       themselves on a single line (except for any surrounding whitespace or
89       trailing comments), and they cannot contain the character "]".
90
91       Every line after a given section label until the next section label (or
92       the end of the config file) belongs to the given section label. If no
93       section label is currently in effect, the current section has an empty
94       label. In other words, there is an implicit:
95
96           []                # Label is the empty string
97
98       at the start of each config file.
99
100       Configuration variables
101
102       Each non-empty line within a section must consist of the specification
103       of a configuration variable. Each such variable consists of a key and a
104       string value. For example:
105
106           name: George
107            age: 47
108
109           his weight! : 185
110
111       The key consists of every character (including internal whitespace)
112       from the start of the line until the key/value separator. So, the
113       previous example declares three keys: 'name', 'age', and 'his weight!'.
114
115       Note that whitespace before and after the key is removed. This makes it
116       easier to format keys cleanly:
117
118                  name : George
119                   age : 47
120           his weight! : 185
121
122       The key/value separator can be either a colon (as above) or an equals
123       sign, like so:
124
125                  name= George
126                   age=  47
127           his weight! = 185
128
129       Both types of separators can be used in the same file, but neither can
130       be used as part of a key. Newlines are not allowed in keys either.
131
132       When writing out a config file, Config::Std tries to preserve whichever
133       separator was used in the original data (if that data was read in). New
134       data (created by code not parsed by "read_config") is written back with
135       a colon as its default separator, unless you specify the only other
136       separator value '=' when the module is loaded:
137
138           use Config::Std { def_sep => '=' };
139
140       Note that this does not change read-in parsing, does not change
141       punctuation for values that were parsed, and will not allow values
142       other than '=' or ':'.
143
144       Everything from the first non-whitespace character after the separator,
145       up to the end of the line, is treated as the value for the config
146       variable.  So all of the above examples define the same three values:
147       'George', '47', and '185'.
148
149       In other words, any whitespace immediately surrounding the separator
150       character is part of the separator, not part of the key or value.
151
152       Note that you can't put a comment on the same line as a configuration
153       variable. The "# etc." is simply considered part of the value:
154
155           [Delimiters]
156
157           block delims:    { }
158           string delims:   " "
159           comment delims:  # \n
160
161       You can comment a config var on the preceding or succeeding line:
162
163           [Delimiters]
164
165           # Use braces to delimit blocks...
166           block delims:    { }
167
168           # Use double quotes to delimit strings
169
170           string delims:   " "
171
172           # Use octothorpe/newline to delimit comments
173           comment delims:  # \n
174
175       Multi-line configuration values
176
177       A single value can be continued over two or more lines. If the line
178       immediately after a configuration variable starts with the separator
179       character used in the variable's definition, then the value of the
180       variable continues on that line. For example:
181
182           address: 742 Evergreen Terrace
183                  : Springfield
184                  : USA
185
186       The newlines then form part of the value, so the value specified in the
187       previous example is: "742 Evergreen Terrace\nSpringfield\nUSA"
188
189       Note that the second and subsequent lines of a continued value are
190       considered to start where the whitespace after the original separator
191       finished, not where the whitespace after their own separator finishes.
192       For example, if the previous example had been:
193
194           address: 742 Evergreen Terrace
195                  :   Springfield
196                  :     USA
197
198       then the value would be:
199
200           "742 Evergreen Terrace\n  Springfield\n    USA"
201
202       If a continuation line has less leading whitespace that the first line:
203
204           address:   742 Evergreen Terrace
205                  :  Springfield
206                  : USA
207
208       it's treated as having no leading whitespace:
209
210           "742 Evergreen Terrace\nSpringfield\nUSA"
211
212       Multi-part configuration values
213
214       If the particular key appears more than once in the same section, it is
215       considered to be part of the same configuration variable. The value of
216       that configuration value is then a list, containing all the individual
217       values for each instance of the key. For example, given the definition:
218
219           cast: Homer
220           cast: Marge
221           cast: Lisa
222           cast: Bart
223           cast: Maggie
224
225       the corresponding value of the 'cast' configuration variable is:
226       "['Homer', 'Marge', 'Lisa', 'Bart', 'Maggie']"
227
228       Individual values in a multi-part list can also be multi-line (see
229       above). For example, given:
230
231           extras: Moe
232                 : (the bartender)
233
234           extras: Smithers
235                 : (the dogsbody)
236
237       the value for the 'extras' config variable is:
238       "["Moe\n(the bartender)", "Smithers\n(the dogsbody)"]"
239
240   Internal representation
241       Each section label in a configuration file becomes a top-level hash key
242       whe the configuration file is read in. The corresponding value is a
243       nested hash reference.
244
245       Each configuration variable's key becomes a key in that nested hash
246       reference.  Each configuration variable's value becomes the
247       corresponding value in that nested hash reference.
248
249       Single-line and multi-line values become strings. Multi-part values
250       become references to arrays of strings.
251
252       For example, the following configuration file:
253
254           # A simple key (just an identifier)...
255           simple : simple value
256
257           # A more complex key (with whitespace)...
258           more complex key : more complex value
259
260           # A new section...
261           [MULTI-WHATEVERS]
262
263           # A value spread over several lines...
264           multi-line : this is line 1
265                      : this is line 2
266                      : this is line 3
267
268           # Several values for the same key...
269           multi-value: this is value 1
270           multi-value: this is value 2
271           multi-value: this is value 3
272
273       would be read into a hash whose internal structure looked like this:
274
275           {
276              # Default section...
277              '' => {
278                 'simple'           => 'simple value',
279                 'more complex key' => 'more complex value',
280              },
281
282              # Named section...
283              'MULTI-WHATEVERS' => {
284                   'multi-line'  => "this is line 1\nthis is line 2\nthis is line 3",
285
286                   'multi-value' => [ 'this is value 1',
287                                      'this is value 2',
288                                      'this is value 3'
289                                    ],
290               }
291           }
292

INTERFACE

294       The following subroutines are exported automatically whenever the
295       module is loaded...
296
297       "read_config($filename => %config_hash)"
298       "read_config($filename => $config_hash_ref)"
299       "read_config($string_ref => %config_hash_or_ref)"
300           The "read_config()" subroutine takes two arguments: the filename of
301           a configuration file, and a variable into which the contents of
302           that configuration file are to be loaded.
303
304           If the variable is a hash, then the configuration sections and
305           their key/value pairs are loaded into nested subhashes of the hash.
306
307           If the variable is a scalar with an undefined value, a reference to
308           an anonymous hash is first assigned to that scalar, and that hash
309           is then filled as described above.
310
311           The subroutine returns true on success, and throws an exception on
312           failure.
313
314           If you pass a reference to the string as the first argument to
315           "read_config()" it uses that string as the source of the config
316           info.  For example:
317
318                   use Config::Std;
319
320                   # here we load the config text to a scalar
321                   my $cfg = q{
322                   [Section 1]
323                   attr1 = at
324                   attr2 = bat
325
326                   [Section 2]
327                   attr3 = cat
328                   };
329
330                   # here we parse the config from that scalar by passing a reference to it.
331                   read_config( \$cfg, my %config );
332
333                   use Data::Dumper 'Dumper';
334                   warn Dumper [ \%config ];
335
336       "write_config(%config_hash => $filename)"
337       "write_config($config_hash_ref => $filename)"
338       "write_config(%config_hash)"
339       "write_config($config_hash_ref)"
340           The "write_config()" subroutine takes two arguments: the hash or
341           hash reference containing the configuration data to be written out
342           to disk, and an optional filename specifying which file it is to be
343           written to.
344
345           The data hash must conform to the two-level structure described
346           earlier: with top-level keys naming sections and their values being
347           references to second-level hashes that store the keys and values of
348           the configuartion variables. If the structure of the hash differs
349           from this, an exception is thrown.
350
351           If a filename is also specified, the subroutine opens that file and
352           writes to it. It no filename is specified, the subroutine uses the
353           name of the file from which the hash was originally loaded using
354           "read_config()". It no filename is specified and the hash wasn't
355           originally loaded using "read_config()", an exception is thrown.
356
357           The subroutine returns true on success and throws and exception on
358           failure.
359
360       If necessary (typically to avoid conflicts with other modules), you can
361       have the module export its two subroutines with different names by
362       loading it with the appropriate options:
363
364           use Config::Std { read_config => 'get_ini', write_config => 'update_ini' };
365
366           # and later...
367
368           get_ini($filename => %config_hash);
369
370           # and later still...
371
372           update_ini(%config_hash);
373
374       You can also control how much spacing the module puts between single-
375       line values when they are first written to a file, by using the
376       "def_gap" option:
377
378           # No empty line between single-line config values...
379           use Config::Std { def_gap => 0 };
380
381           # An empty line between all single-line config values...
382           use Config::Std { def_gap => 1 };
383
384       Regardless of the value passed for "def_gap", new multi-line values are
385       always written with an empty line above and below them. Likewise,
386       values that were previously read in from a file are always written back
387       with whatever spacing they originally had.
388

DIAGNOSTICS

390       Can't open config file '%s' (%s)
391           You tried to read in a configuration file, but the file you
392           specified didn't exist. Perhaps the filepath you specified was
393           wrong. Or maybe your application didn't have permission to access
394           the file you specified.
395
396       Can't read from locked config file '$filename'
397           You tried to read in a configuration file, but the file you
398           specified was being written by someone else (they had a file lock
399           active on it).  Either try again later, or work out who else is
400           using the file.
401
402       Scalar second argument to 'read_config' must be empty
403           You passed a scalar variable as the destination into
404           "read_config()" was supposed to load a configuration file, but that
405           variable already had a defined value, so "read_config()" couldn't
406           autovivify a new hash for you. Did you mean to pass the subroutine
407           a hash instead of a scalar?
408
409       Can't save %s value for key '%s' (only scalars or array refs)
410           You called "write_config" and passed it a hash containing a
411           configuration variable whose value wasn't a single string, or a
412           list of strings. The configuration file format supported by this
413           module only supports those two data types as values. If you really
414           need to store other kinds of data in a configuration file, you
415           should consider using "Data::Dumper" or "YAML" instead.
416
417       Missing filename in call to write_config()
418           You tried to calll "write_config()" with only a configuration hash,
419           but that hash wasn't originally loaded using "read_config()", so
420           "write_config()" has no idea where to write it to. Either make sure
421           the hash you're trying to save was originally loaded using
422           "read_config()", or else provide an explicit filename as the second
423           argument to "write_config()".
424
425       Can't open config file '%s' for writing (%s)
426           You tried to update or create a configuration file, but the file
427           you specified could not be opened for writing (for the reason given
428           in the parentheses). This is often caused by incorrect filepaths or
429           lack of write permissions on a directory.
430
431       Can't write to locked config file '%s'
432           You tried to update or create a configuration file, but the file
433           you specified was being written at the time by someone else (they
434           had a file lock active on it). Either try again later, or work out
435           who else is using the file.
436

CONFIGURATION AND ENVIRONMENT

438       Config::Std requires no configuration files or environment variables.
439       (To do so would be disturbingly recursive.)
440

DEPENDENCIES

442       This module requires the Class::Std module (available from the CPAN)
443

INCOMPATIBILITIES

445       Those variants of INI file dialect supporting partial-line comment are
446       incompatible.  (This is the price of keeping comments when re-writing.)
447

BUGS AND LIMITATIONS

449       Memory leak re-reading
450           A daemon re-reading its config file has reported a memory leak.
451
452       Parallel testing not safe
453           This is a config file module. Tests written before "TAP" got
454           parallel testing are unsafe with parallel testing, surprise!
455           Settings are now included to force serial testing (until we
456           refactor all tests to use temp dirs?).
457
458           If using an older Perl < 5.21.1, and Module.PL, and getting out-of-
459           sequence test failures installing this module, either update
460           Test::Harness~'>= 3.31' or export HARNESS_OPTIONS=j1 (or
461           force/no-test, or use Build.PL and/or perl-5.22.0 or newer
462           instead).
463
464       Loading on demand
465           If you attempt to load "read_config()" and "write_config()" at
466           runtime with "require", you can not rely upon the prototype to
467           convert a regular hash to a reference. To work around this, you
468           must explicitly pass a reference to the config hash.
469
470               require Config::Std;
471               Config::Std->import;
472
473               my %config;
474               read_config($file, \%config);
475               write_config(\%config, $file);
476
477       Windows line endings on Unix/Linux (RT#21547/23550)
478           If the config file being read contains carriage returns and line
479           feeds at the end of each line rather than just line feeds (i.e. the
480           standard Windows file format, when read on a machine expecting
481           POSIX file format), Config::Std emits an error with embedded
482           newline.
483
484           Workaround is match file line-endings to locale.
485
486           This will be fixed in 1.000.
487
488       leading comment vanishes (RT#24597,)
489           A comment before the first section is not always retained on write-
490           back, if the '' default section is empty.
491
492       Please report any bugs or feature requests to
493       "bug-config-std@rt.cpan.org", or through the web interface at
494       <http://rt.cpan.org>.
495

AUTHOR

497       Damian Conway  "<DCONWAY@cpan.org>" Maintainers Bill Ricker
498       "<BRICKER@cpan.org>" Tom Metro      "<tmetro@cpan.org>"
499
501       Copyright (c) 2005, Damian Conway "<DCONWAY@cpan.org>".  Copyright (c)
502       2011,2014,2017, D.Conway, W.Ricker "<BRICKER@cpan.org>" All rights
503       reserved.
504
505       This module is free software; you can redistribute it and/or modify it
506       under the same terms as Perl itself.
507

DISCLAIMER OF WARRANTY

509       BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
510       FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT
511       WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER
512       PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND,
513       EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
514       WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
515       ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH
516       YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL
517       NECESSARY SERVICING, REPAIR, OR CORRECTION.
518
519       IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
520       WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
521       REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE
522       TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR
523       CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
524       SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
525       RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
526       FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
527       SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
528       DAMAGES.
529
530
531
532perl v5.34.0                      2022-01-21                    Config::Std(3)
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