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ArgvFile(3)	      User Contributed Perl Documentation	   ArgvFile(3)

NAME
       Getopt::ArgvFile - interpolates script options from files into @ARGV or
       another array

VERSION
       This manual describes version 1.11.

SYNOPSIS
       One line invocation - option hints are processed while the module is
       loaded:

	 # load module and process option file hints in @ARGV
	 use Getopt::ArgvFile default=>1;

	 # load another module to evaluate the options, e.g.:
	 use Getopt::Long;
	 ...

	 # evaluate options, e.g. this common way:
	 GetOptions(\%options, 'any');	  # this function is defined in Getopt::Long

       Or suppress option hint processing when the module is loaded, to
       perform it later on:

	 # load module, do *not* process option file hints
	 use Getopt::ArgvFile justload=>1;

	 # load another module to evaluate the options, e.g.:
	 use Getopt::Long;
	 ...

	 # *now*, solve option file hints
	 Getopt::ArgvFile::argvFile(default=>1);

	 # evaluate options, e.g. this common way:
	 GetOptions(\%options, 'any');	  # this function is defined in Getopt::Long

       Or use the traditional two step invocation of module loading with
       symbol import and explicit option file handling:

	 # Load the module and import the &argvFile symbol
	 # - this will *not* process option hints.
	 # Use *this* syntax to do so, *exactly*.
	 use Getopt::ArgvFile qw(argvFile);

	 # load another module to evaluate the options, e.g.:
	 use Getopt::Long;
	 ...

	 # *now*, solve option file hints
	 argvFile(default=>1);

	 # evaluate options, e.g. this common way:
	 GetOptions(\%options, 'any');	  # this function is defined in Getopt::Long

       If options should be processed into another array, this can be done
       this way:

	 # prepare target array
	 my @options=('@options1', '@options2', '@options3');

	 ...

	 # replace file hints by the options stored in the files
	 argvFile(array=>\@options);

       In case you do not like the "@" prefix it is possible to define an
       option to be used instead:

	 # prepare target array
	 my @options=('-options', 'options1', '-options', 'options2');

	 ...

	 # replace file hints by the options stored in the files
	 argvFile(fileOption=>'options', array=>\@options);

DESCRIPTION
       This module simply interpolates option file hints in @ARGV by the
       contents of the pointed files. This enables option reading from files
       instead of or additional to the usual reading from the command line.

       Alternatively, you can process any array instead of @ARGV which is used
       by default and mentioned mostly in this manual.

       The interpolated @ARGV could be subsequently processed by the usual
       option handling, e.g. by a Getopt::xxx module.  Getopt::ArgvFile does
       not perform any option handling itself, it only prepares the array
       @ARGV.

       Option files can significantly simplify the call of a script.  Imagine
       the following:

       Breaking command line limits
	   A script may offer a lot of options, with possibly a few of them
	   even taking parameters. If these options and their parameters are
	   passed onto the program call directly, the number of characters
	   accepted by your shells command line may be exceeded.

	   Perl itself does not limit the number of characters passed to a
	   script by parameters, but the shell or command interpreter often
	   sets a limit here. The same problem may occur if you want to store
	   a long call in a system file like crontab.

	   If such a limit restricts you, options and parameters may be moved
	   into option files, which will result in a shorter command line
	   call.

       Script calls prepared by scripts
	   Sometimes a script calls another script. The options passed onto
	   the nested script could depend on variable situations, such as a
	   users input or the detected environment. In such a case, it can be
	   easier to generate an intermediate option file which is then passed
	   to the nested script.

	   Or imagine two cron jobs one preparing the other: the first may
	   generate an option file which is then used by the second.

       Simple access to typical calling scenarios
	   If several options need to be set, but in certain circumstances are
	   always the same, it could become sligthly nerveracking to type them
	   in again and again. With an option file, they can be stored once
	   and recalled easily as often as necessary.

	   Further more, option files may be used to group options. Several
	   settings may set up one certain behaviour of the program, while
	   others influence another. Or a certain set of options may be useful
	   in one typical situation, while another one should be used
	   elsewhere. Or there is a common set of options which has to be used
	   in every call, while other options are added depending on the
	   current needs. Or there are a few user groups with different but
	   typical ways to call your script.  In all these cases, option files
	   may collect options belonging together, and may be combined by the
	   script users to set up a certain call.  In conjunction with the
	   possiblity to nest such collections, this is perhaps the most
	   powerful feature provided by this method.

       Individual and installationwide default options
	   The module allows the programmer to enable user setups of default
	   options; for both individual users or generally all callers of a
	   script.  This is especially useful for administrators who can
	   configure the default behaviour of a script by setting up its
	   installationwide startup option file. All script users are free
	   then to completely forget every already configured setup option.
	   And if one of them regularly adds certain options to every call, he
	   could store them in his individual startup option file.

	   For example, I use this feature to make my scripts both flexible
	   and usable. I have several scripts accessing a database via DBI.
	   The database account parameters as well as the DBI startup settings
	   should not be coded inside the scripts because this is not very
	   flexible, so I implemented them by options. But on the other hand,
	   there should be no need for a normal user to pass all these
	   settings to every script call. My solution for this is to use
	   default option files set up and maintained by an administrator.
	   This is very transparent, most of the users know nothing of these
	   (documented ;-) configuration settings ... and if anything changes,
	   only the option files have to be adapted.

EXPORTS
       No symbol is exported by default, but you may explicitly import the
       "argvFile()" function using the exact syntax of the following example:

	 use Getopt::ArgvFile qw(argvFile);

       Please note that this interface is provided for backwards compatibility
       with versions up to 1.06. By loading the module this way, the
       traditional import mechanisms take affect and "argvFile()" is not
       called implicitly.

       This means that while option file hints are usually processed
       implicitly when "Getopt::ArgvFile" is loaded, the syntax

	 use Getopt::ArgvFile qw(argvFile);

       requires an extra call of argvFile() to process option files.

FUNCTIONS
       There is only one function, argvFile(), which does all the work of
       option file hint processing.

       Please note that with version 1.07 and above "argvFile()" is called
       implicitly when the module is loaded, except this is done in one of the
       following ways:

	 # the traditional interface - provided for
	 # backwards compatibility - this loads the
	 # module and imports the &argvFile symbol
	 use Getopt::ArgvFile qw(argvFile);

	 --

	 # option file processing is explicitly suppressed
	 use Getopt::ArgvFile justload=>1;

       Except for the traditional loading, the complete interface of
       "argvFile()" is available via "use", but in the typical "use" syntax
       without parantheses.

	 # implicit call of argvFile(default=>1, home=>1)
	 use Getopt::ArgvFile default=>1, home=>1;

       See ONE LINE INVOCATION for further details.

   argvFile()
       Scans the command line parameters (stored in @ARGV or an alternatively
       passed array) for option file hints (see Basics below), reads the
       pointed files and makes their contents part of the source array (@ARGV
       by default) replacing the hints.

       Because the function was intentionally designed to work on @ARGV and
       this is still the default behaviour, this manual mostly speaks about
       @ARGV. Please note that it is possible to process any other array as
       well.

       Basics

       An option file hint is simply the filename preceeded by (at least) one
       "@" character:

	 > script -optA argA -optB @optionFile -optC argC

       This will cause argvFile() to scan "optionFile" for options.  The
       element "@optionFile" will be removed from the @ARGV array and will be
       replaced by the options found.

       Note: you can choose another prefix by using the "prefix" parameter,
       see below.

       An option file which cannot be found is quietly skipped.

       Well, what is within an option file? It is intended to store command
       line arguments which should be passed to the called script. They can be
       stored exactly as they would be written in the command line, but may be
       spread to multiple lines. To make the file more readable, space and
       comment lines (starting with a "#") are allowed additionally. POD
       comments are supported as well.	For example, the call

	 > script -optA argA -optB -optC cArg par1 par2

       could be transformed into

	 > script @scriptOptions par1 par2

       where the file "scriptOptions" may look like this:

	 # option a
	 -optA argA

       ""

	 =pod
	 option b
	 =cut
	 -optB

       ""

	 # option c
	 -optC cArg

       Nested option files

       Option files can be nested. Recursion is avoided globally, that means
       that every file will be opened only once (the first time argvFile()
       finds a hint pointing to it). This is the simplest implementation,
       indeed, but should be suitable. (Unfortunately, there are LIMITS.)

       By using this feature, you may combine groups of typical options into a
       top level option file, e.g.:

	 File ab:

       ""

	 # option a
	 -optA argA
	 # option b
	 -optB

       ""

	 File c:

       ""

	 # option c
	 -optC cArg

       ""

	 File abc:

       ""

	 # combine ab and c
	 @ab @c

       If anyone provides these files, a user can use a very short call:

	 > script @abc

       and argvFile() will recursively move all the filed program parameters
       into @ARGV.

       Relative pathes

       Pathes in option files might be relative, as in

	 -file ../file @../../configs/nested

       If written with the (prepared) start directory in mind, that will work,
       but it can fail when it was written relatively to the option file
       location because by default those pathes will not be resolved when
       written from an option file.

       Use parameter "resolveRelativePathes" to switch to path resolution:

	  argvFile(resolveRelativePathes=>1);

       will cause "argvFile()" to expand those pathes, both in standard
       strings and nested option files.

	  With resolveRelativePathes, both pathes
	  will be resolved:

	  -file ../file @../../configs/nested

       A path is resolved relative to the option file it is found in.

       Environment variables

       Similar to relative pathes, environment variables are handled
       differently depending if the option is specified at the commandline or
       from an option file, due to bypassed shell processing. By default,
       "argvFile()" does not resolve environment variables. But if required it
       can be commanded to do so via parameter "resolveEnvVars".

	 argvFile(resolveEnvVars=>1);

       Startup support

       By setting several named parameters, you can enable automatic
       processing of startup option files. There are three of them:

       The default option file is searched in the installation path of the
       calling script, the home option file is searched in the users home
       (evaluated via environment variable "HOME"), and the current option
       script is searched in the current directory.

       By default, all startup option files are expected to be named like the
       script, preceeded by a dot, but this can be adapted to individual needs
       if preferred, see below.

	Examples:
	 If a script located in "/path/script" is invoked in directory
	 /the/current/dir by a user "user" whoms "HOME" variable points
	 to "/homes/user", the following happens:

       ""

	 argvFile()		       # ignores all startup option files;
	 argvFile(default=>1)	       # searches and expands "/path/.script",
				       # if available (the "default" settings);
	 argvFile(home=>1)	       # searches and expands "/homes/user/.script",
				       # if available (the "home" settings);
	 argvFile(current=>1)	       # searches and expands "/the/current/dir/.script",
				       # if available (the "current" settings);
	 argvFile(
		  default => 1,
		  home	  => 1,
		  current => 1
		 )		       # tries to handle all startups.

       Any true value will activate the setting it is assigned to.

       In case the ".script" name rule does not meet your needs or does not
       fit into a certain policy, the expected startup filenames can be set up
       by an option "startupFilename". The option value may be a scalar used
       as the expected filename, or a reference to an array of accepted
       choices, or a reference to code returning the name - plainly or as a
       reference to an array of names. Such callback code will be called once
       and will receive the name of the script.

	 # use ".config"
	 argvFile(startupFilename => '.config');

	 # use ".config" or "config"
	 argvFile(startupFilename => [qw(.config config)]);

	 # emulate the default behaviour,
	 # but use an extra dot postfix
	 my $nameBuilder=sub {join('', '.', basename($_[0]), '.');};
	 argvFile(startupFilename => $nameBuilder);

	 # use .(script)rc or .(script)/config
	 my $nameBuilder=sub
			  {
			   my $sname=basename($_[0]);
			   [".${sname}rc", ".${sname}/config"];
			  };
	 argvFile(startupFilename => $nameBuilder);

       Note that the list variants will use the first matching filename in
       each possible startup-file path. For example if your array is
       "['.scriptrc', '.script.config']" and you have both a ".scriptrc" and a
       ".script.config" file in (say) your current directory, only the
       ".scriptrc" file will be used, as it is the first found.

       The contents found in a startup file is placed before all explicitly
       set command line arguments. This enables to overwrite a default setting
       by an explicit option. If all startup files are read, current startup
       files can overwrite home files which have preceedence over default
       ones, so that the default startups are most common. In other words, if
       the module would not support startup files, you could get the same
       result with "script @/path/.script @/homes/user/.script
       @/the/current/dir/.script".

       Note: There is one certain case when overwriting will not work
       completely because duplicates are sorted out: if all three types of
       startup files are used and the script is started in the installation
       directory, the default file will be identical to the current file. The
       default file is processed, but the current file is skipped as a
       duplicate later on and will not overwrite settings made caused by the
       intermediately processed home file.  If started in another directory,
       it will overwrite the home settings.  But the alternative seems to be
       even more confusing: the script would behave differently if just
       started in its installation path. Because a user might be more aware of
       configuration editing then of the current path, I choose the current
       implementation, but this preceedence might become configurable in a
       future version.

       If there is no HOME environment variable, the home setting takes no
       effect to avoid trouble accessing the root directory.

       Cascades

       The function supports multi-level (or so called cascaded) option files.
       If a filename in an option file hint starts with a "@" again, this
       complete name is the resolution written back to @ARGV - assuming there
       will be another utility reading option files.

	Examples:
	 @rfile		 rfile will be opened, its contents is
			 made part of @ARGV.
	 @@rfile	 cascade: "@rfile" is written back to
			 @ARGV assuming that there is a subsequent
			 tool called by the script to which this
			 hint will be passed to solve it by an own
			 call of argvFile().

       The number of cascaded hints is unlimited.

       Processing an alternative array

       Although the function was designed to process @ARGV, it is possible to
       process another array as well if you prefer. To do this, simply pass a
       reference to this array by parameter array.

	Examples:
	 argvFile()		       # processes @ARGV;
	 argvFile(array=>\@options);   # processes @options;

       Choosing an alternative hint prefix

       By default, "@" is the prefix used to mark an option file. This can be
       changed by using the optional parameter prefix:

	Examples:
	 argvFile();		       # use "@";
	 argvFile(prefix=>'~');	       # use "~";

       Note that the strings "#", "=", "-" and "+" are reserved and cannot be
       chosen here because they are used to start plain or POD comments or are
       typically option prefixes.

       Using an option instead of a hint prefix

       People not familiar with option files might be confused by file
       prefixes.  This can be avoided by offering an option that can be used
       instead of a prefix, using the optional parameter fileOption:

	 # install a file option
	 # (all lines are equivalent)
	 argvFile(fileOption=>'options');
	 argvFile(fileOption=>'-options');
	 argvFile(fileOption=>'+options');
	 argvFile(fileOption=>'--options');

       The name of the option can be specified with or without the usual
       option prefixes "-", "--" and "+".

       Once an option is declared, it can replace a prefix. (Prefixes remain
       in action as well.)

	  # with -options declared to be a file option,
	  # these sequences are equivalent
	  @file
	  -options file

	  # five equivalent cascades
	  @@@@file
	  -options @@@file
	  -options -options @@file
	  -options -options -options @file
	  -options -options -options -options file

       Please note that prefixes are attached to the filename with no spaces
       in between, while the option declared via -fileOption is separated from
       the filename by whitespace, as for normal options.

ONE LINE INVOCATION
       The traditional two line sequence

	 # load the module
	 use Getopt::ArgvFile qw(argvFile);

	 ...

	 # solve option files
	 argvFile(default=>1);

       can be reduced to one line - just pass the parameters of "argvFile()"
       to "use()":

	 # load module and process option file hints in @ARGV
	 use Getopt::ArgvFile default=>1;

       Please note that in this case option file hints are processed at
       compile time. This means that if you want to process alternative
       arrays, these arrays have to be prepared before, usually in a "BEGIN"
       block.

       In versions 1.07 and above, implicit option file handling is the
       default and only suppressed for the traditional

	 use Getopt::ArgvFile qw(argvFile);

       loading, for reasons of backwards compatibility. A simple loading like

	 use Getopt::ArgvFile;

       will process option hints! If you want to suppress this, use the
       "justload" switch:

	 use Getopt::ArgvFile justload=>1;

       See FUNCTIONS for additional informations.

NOTES
       If a script calling "argvFile()" with the "default" switch is invoked
       using a relative path, it is strongly recommended to perform the call
       of "argvFile()" in the startup directory because "argvFile()" then uses
       the relative script path as well.

LIMITS
       If an option file does not exist, argvFile() simply ignores it.	No
       message will be displayed, no special return code will be set.

AUTHOR
       Jochen Stenzel <mailto:perl@jochen-stenzel.de>

LICENSE
       Copyright (c) 1993-2007 Jochen Stenzel. All rights reserved.

       This program is free software, you can redistribute it and/or modify it
       under the terms of the Artistic License distributed with Perl version
       5.003 or (at your option) any later version. Please refer to the
       Artistic License that came with your Perl distribution for more
       details.

perl v5.16.2			  2007-04-21			   ArgvFile(3)
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