getopt(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 per-
form 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 sym-
bol 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 con-
tents 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 else-
where. 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 pow-
erful 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 con-
figure the default behaviour of a script by setting up its instal-
lationwide 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 set-
tings 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 (docu-
mented ;-) 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 tradi-
tional import mechanisms take affect and "argvFile()" is not called
implicitly.
This means that while option file hints are usually processed implic-
itly 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 "argv-
File()" 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 ele-
ment "@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 com-
ments 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 loca-
tion 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 differ-
ently depending if the option is specified at the commandline or from
an option file, due to bypassed shell processing. By default, "argv-
File()" 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 process-
ing 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/cur-
rent/dir/.script".
Note: There is one certain case when overwriting will not work com-
pletely 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 dupli-
cate later on and will not overwrite settings made caused by the inter-
mediately 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 configura-
tion editing then of the current path, I choose the current implementa-
tion, but this preceedence might become configurable in a future ver-
sion.
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 com-
plete 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 pre-
fixes. 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 com-
pile 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 "just-
load" 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 Artis-
tic License that came with your Perl distribution for more details.
perl v5.8.8 2007-04-21 ArgvFile(3)
See also Getopt::Long(3)
Man(1) output converted with
man2html