SIMPLE CONFIGURATION FILE¶

Simple syntax is what you need for most of your projects. These are, as the name asserts, the simplest. File consists of key/value pairs, delimited by nothing but white space. Keys (variables) should be strictly alpha-numeric with possible dashes (-). Values can hold any arbitrary text. Here is an example of such a configuration file:

  Alias     /exec
  TempFile  /usr/tmp

Comments start with a pound ('#') sign and cannot share the same line with other configuration data.

HTTP-LIKE SYNTAX¶

This format of separating key/value pairs is used by HTTP messages. Each key/value is separated by semi-colon (:). Keys are alphanumeric strings with possible '-'. Values can be any arbitrary text:

Example:

  Alias: /exec
  TempFile: /usr/tmp

It is OK to have spaces around ':'. Comments start with '#' and cannot share the same line with other configuration data.

INI-FILE¶

These configuration files are more native to Win32 systems. Data is organized in blocks. Each key/value pair is delimited with an equal (=) sign. Blocks are declared on their own lines enclosed in '[' and ']':

  [BLOCK1]
  KEY1=VALUE1
  KEY2=VALUE2
  [BLOCK2]
  KEY1=VALUE1
  KEY2=VALUE2

Your Winamp 2.x play list is an example of such a configuration file.

This is the perfect choice if you need to organize your configuration file into categories:

  [site]
  url="http://www.handalak.com"
  title="Web site of a \"Geek\""
  author=sherzodr
  [mysql]  
  dsn="dbi:mysql:db_name;host=handalak.com"
  user=sherzodr
  password=marley01

SIMPLIFIED INI-FILE¶

These files are pretty much similar to traditional ini-files, except they don't have any block declarations. This style is handy if you do not want any categorization in your configuration file, but still want to use '=' delimited key/value pairs. While working with such files, Config::Simple assigns them to a default block, called 'default' by default :-).

  url = "http://www.handalak.com"

Comments can begin with either pound ('#') or semi-colon (';'). Each comment should reside on its own line

READING THE CONFIGURATION FILE¶

To be able to use more features of the library, you will need to use its object interface:

  $cfg = new Config::Simple('app.cfg');

The above line reads and parses the configuration file accordingly. It tries to guess which syntax is used by passing the file to guess_syntax() method. Alternatively, you can create an empty object, and only then read the configuration file in:

  $cfg = new Config::Simple();
  $cfg->read('app.cfg');

As in the first example, read() also calls guess_syntax() method on the file.

If, for any reason, it fails to guess the syntax correctly (which is less likely), you can try to debug by using its guess_syntax() method. It expects file handle for a configuration file and returns the name of a syntax. Return value is one of "ini", "simple" or "http".

  open(FH, "app.cfg");
  printf("This file uses '%s' syntax\n", $cfg->guess_syntax(\*FH));

ACCESSING VALUES¶

After you read the configuration file in successfully, you can use param() method to access the configuration values. For example:

  $user = $cfg->param("User");

will return the value of "User" from either simple configuration file, or http-styled configuration as well as simplified ini-files. To access the value from a traditional ini-file, consider the following syntax:

  $user = $cfg->param("mysql.user");

The above returns the value of "user" from within "[mysql]" block. Notice the use of dot "." to delimit block and key names.

Config::Simple also supports vars() method, which, depending on the context used, returns all the values either as hashref or hash:

  my %Config = $cfg->vars();
  print "Username: $Config{User}";
  # If it was a traditional ini-file:
  print "Username: $Config{'mysql.user'}";

If you call vars() in scalar context, you will end up with a reference to a hash:

  my $Config = $cfg->vars();
  print "Username: $Config->{User}";

If you know what you're doing, you can also have an option of importing all the names from the configuration file into your current name space as global variables. All the block/key names will be uppercased and will be converted to Perl's valid variable names; that is, all the dots (block-key separator) and other '\W' characters will be substituted with underscore '_':

  $cfg = new Config::Simple('app.cfg');
  $cfg->import_names();
  # or, with a single line:
  Config::Simple->new('app.cfg')->import_names();
  
  print STDERR "Debugging mode is on" if $DEBUG_MODE;

In the above example, if there was a variable 'mode' under '[debug]' block, it will be now accessible via $DEBUG_MODE, as opposed to $cfg->param('debug.mode');

"import_names()" by default imports the values to its caller's name space. Optionally, you can specify where to import the values by passing the name of the name space as the first argument. It also prevents potential name collisions:

  Config::Simple->new('app.cfg')->import_names('CFG');
  print STDERR "Debugging mode is on" if $CFG::DEBUG_MODE;

If all you want is to import values from a configuration file, the above syntax may still seem longer than necessary. That's why Config::Simple supports import_from() - class method, which is called with the name of the configuration file. It will call import_names() for you:

  Config::Simple->import_from('app.cfg');

The above line imports all the variables into the caller's name space. It's similar to calling import_names() on an object. If you pass a string as the second argument, it will treat it as the alternative name space to import the names into. As we already showed in the very first example, you can also pass a reference to an existing hash as the second argument. In this case, that hash will be modified with the values of the configuration file.

  # import into $CFG name space:
  Config::Simple->import_from('app.cfg', 'CFG');
  # import into %Config hash:
  Config::Simple->import_from('app.cfg', \%Config);

The above line imports all the values to 'CFG' name space. import_from() returns underlying Config::Simple object (which you may not even need anymore):

  $cfg = Config::Simple->import_from('app.cfg', \my %Config);
  $cfg->write('app.cfg.bak');

UPDATING THE VALUES¶

Configuration values, once read into Config::Simple, can be updated from within your program by using the same param() method used for accessing them. For example:

  $cfg->param("User", "sherzodR");

The above line changes the value of "User" to "sherzodR". Similar syntax is applicable for ini-files as well:

  $cfg->param("mysql.user", "sherzodR");

If the key you're trying to update does not exist, it will be created. For example, to add a new "[session]" block to your ini-file, assuming this block doesn't already exist:

  $cfg->param("session.life", "+1M");

You can also delete values calling delete() method with the name of the variable:

  $cfg->delete('mysql.user'); # deletes 'user' under [mysql] block

SAVING/WRITING CONFIGURATION FILES¶

The above updates to the configuration values are in-memory operations. They do not reflect in the file itself. To modify the files accordingly, you need to call either "write()" or "save()" methods on the object:

  $cfg->write();

The above line writes the modifications to the configuration file. Alternatively, you can pass a name to either write() or save() to indicate the name of the file to create instead of modifying existing configuration file:

  $cfg->write("app.cfg.bak");

If you want the changes saved at all times, you can turn "autosave" mode on by passing true value to $cfg->autosave(). It will make sure before your program is terminated, all the configuration values are written back to its file:

  $cfg = new Config::Simple('aff.cfg');
  $cfg->autosave(1);

CREATING CONFIGURATION FILES¶

Occasionally, your programs may want to create their own configuration files on the fly, possibly from a user input. To create a configuration file from scratch using Config::Simple, simply create an empty configuration file object and define your syntax. You can do it by either passing "syntax" option to new(), or by calling syntax() method. Then play with param() method as you normally would. When you're done, call write() method with the name of the configuration file:

  $cfg = new Config::Simple(syntax=>'ini');
  # or you could also do:
  # $cfg->autosave('ini')
  $cfg->param("mysql.dsn", "DBI:mysql:db;host=handalak.com");
  $cfg->param("mysql.user", "sherzodr");
  $cfg->param("mysql.pass", 'marley01');
  $cfg->param("site.title", 'sherzodR "The Geek"');
  $cfg->write("new.cfg");

This creates a file "new.cfg" with the following content:

  ; Config::Simple 4.43
  ; Sat Mar  8 00:32:49 2003
  [site]
  title=sherzodR "The Geek"
  [mysql]
  pass=marley01
  dsn=DBI:mysql:db;host=handalak.com
  user=sherzodr

Neat, huh? Supported syntax keywords are "ini", "simple" or "http". Currently there is no support for creating simplified ini-files.

MULTIPLE VALUES¶

Ever wanted to define array of values in your single configuration variable? I have! That's why Config::Simple supports this fancy feature as well. Simply separate your values with a comma:

  Files hp.cgi, template.html, styles.css

Now param() method returns an array of values:

  @files = $cfg->param("Files");
  unlink $_ for @files;

If you want a comma as part of a value, enclose the value(s) in double quotes:

  CVSFiles "hp.cgi,v", "template.html,v", "styles.css,v"

In case you want either of the values to hold literal quote ("), you can escape it with a backlash:

  SiteTitle "sherzod \"The Geek\""

TIE INTERFACE¶

If OO style intimidates you, and "import_from()" is too simple for you, Config::Simple also supports tie() interface. This interface allows you to tie() an ordinary Perl hash to the configuration file. From that point on, you can use the variable as an ordinary Perl hash.

  tie %Config, "Config::Simple", 'app.cfg';
  # Using %Config as an ordinary hash
  print "Username is '$Config{User}'\n";
  $Config{User} = 'sherzodR';

The difference between "import_from($file, \%Hash)" is, all the changes you make to the hash after tie()ing it, will also reflect in the configuration file object. If autosave() was turned on, they will also be written back to file:

  tie %Config, "Config::Simple", "app.cfg";
  tied(%Config)->autosave(1);

To access the method provided in OO syntax, you need to get underlying Config::Simple object. You can do so with tied() function:

  tied(%Config)->write();

WARNING: tie interface is experimental and not well tested yet. Let me know if you encounter a problem.

CASE SENSITIVITY¶

By default, configuration file keys and values are case sensitive. Which means, $cfg->param("User") and $cfg->param("user") are referring to two different values. But it is possible to force Config::Simple to ignore cases all together by enabling "-lc" switch while loading the library:

  use Config::Simple ('-lc');

WARNING: If you call write() or save(), while working on "-lc" mode, all the case information of the original file will be lost. So use it if you know what you're doing.

USING QUOTES¶

Some people suggest if values consist of none alpha-numeric strings, they should be enclosed in double quotes. Well, says them! Although Config::Simple supports parsing such configuration files already, it doesn't follow this rule while writing them. If you really need it to generate such compatible configuration files, "-strict" switch is what you need:

  use Config::Simple '-strict';

Now, when you write the configuration data back to files, if values hold any none alpha-numeric strings, they will be quoted accordingly. All the double quotes that are part of the value will be escaped with a backslash.

EXCEPTION HANDLING¶

Config::Simple doesn't believe in dying that easily (unless you insult it using wrong syntax). It leaves the decision to the programmer implementing the library. You can use its error() - class method to access underlying error message. Methods that require you to check for their return values are read() and write(). If you pass filename to new(), you will need to check its return value as well. They return any true value indicating success, undef otherwise:

  # following new() always returns true:
  $cfg = new Config::Simple();
  # read() can fail:
  $cfg->read('app.cfg') or die $cfg->error();
  # following new() can fail:
  $cfg = new Config::Simple('app.cfg') or die Config::Simple->error();
  # import_from() calls read(), so it can fail:
  Config::Simple->import_from('app.cfg', \%Config) or die Config::Simple->error();
  # write() may fail:
  $cfg->write() or die $cfg->error();
  # tie() may fail, since it calls new() with a filename
  tie %Config, "Config::Simple", 'app.cfg' or die Config::Simple->error();