S
stevetuckner
What is Usage?
===========
Usage is simple way to access command line parameters for quick scripts
that you write where you don't want to even think about command line
processing. It handles many simple cases but does not have enough power
to handle complicated option processing.
How can I get it?
============
gem install Usage
Where is it at?
=============
http://raa.ruby-lang.org/project/usage/
Show me some examples
=================
1. Simple Usage
The only thing you have remember to use usage are how commands are
usually documented.
First you need to require the usage library:
require "Usage"
Then set up the usage string for the command:
usage = Usage.new "infile outfile"
The above would be a command with two require arguments: an input file
and an output file.
To access those arguments, you just need to use the usage variable that
was created and
send the .infile or .outfile message to them.
File.open(usage.infile) do |fi|
File.open(usage.outfile, "w") do |fo|
fo.write(fi.read)
end
end
If the user doesn't supply the correct number of arguments, the program
exits with an error
and the usage for the program (hence the libraries name).
PROGRAM: test.rb
ERROR: too few arguments 2 expected, 0 given
USAGE: test.rb infile outfile
2. Lists of files (...)
You can write a program that accepts a list of files by using elipses
appended to an
argument (the following program concatenates the input files into one
output file).
usage = Usage.new "outfile infiles..."
File.open(usage.outfile, "w") do |fo|
usage.infiles.each do |infile|
File.open(usage.infile) { |fi| fo.write(fi.read)}
end
end
3. Optional arguments
You can have optional arguments by surounding them in square brackets.
usage = Usage.new "required_arg [optional_arg] "
These are accessed in the standard way
usage.optional_arg # this is nil if it is not given by the user
usage.required_arg
4. Options
You can have dash options that are either required or optional. Options
can also have
arguments associated with them.
usage = Usage.new "[-y] [-x excluded_tags] (-z ztag) (-w
warning_arg) files..."
The options are accessed with "dash_" prefixing the option so that the
-y is accessed
via .dash_y. The -x can be accessed either with #dash_x (which would be
either nil or
true) or #excluded_tags (which would be either nil or the argument for
the -x option).
The -z option is required and has one argument, also the -w option is
also required.
They can appear in any order (-z option first or -w option first). The
optional arguments
can appear either before, interspersed with, or after the required options.
5. Long Options
You can also have long options by including lines following the initial
usage line that
associates the short options with the long ones. Example below:
usage = Usage.new "-x files...", <<EOT
-x,--exclusive specifies exclusive access to the files
EOT
With this case, now #dash_x and #exclusive give the same result when
applied to the usage
variable.
6. Typed options
In order to remove a step and improve argument checking, you can also
add in a "type"
character to identify its type. The characters I used are somewhat
arbitrary. Some of
them I took from BASIC which I programmed in long long ago.
% - Integer
$ - String (but this is unnecessary as this is default)
# - Float
@ - Date-Time
So when you send the argument message to the usage object, you will get
a value of that
type and if the user does not give that type, then they get an error
message.
usage = Usage.new "%num_times @on_date"
In this example, #num_times returns and Integer object and #on_date
returns a Time object.
7. Choice options
You can have optional options that have a set of values which they can
be. The choices
are separated by pipe symbols. See below:
usage = Usage.new "[-a coffee|tea|milk]"
After this #dash_a will give the string coffee, tea, or milk. If the
value given isn't
one of the given choices, then the user is given an error message with the
appropriate choices.
Steve Tuckner
===========
Usage is simple way to access command line parameters for quick scripts
that you write where you don't want to even think about command line
processing. It handles many simple cases but does not have enough power
to handle complicated option processing.
How can I get it?
============
gem install Usage
Where is it at?
=============
http://raa.ruby-lang.org/project/usage/
Show me some examples
=================
1. Simple Usage
The only thing you have remember to use usage are how commands are
usually documented.
First you need to require the usage library:
require "Usage"
Then set up the usage string for the command:
usage = Usage.new "infile outfile"
The above would be a command with two require arguments: an input file
and an output file.
To access those arguments, you just need to use the usage variable that
was created and
send the .infile or .outfile message to them.
File.open(usage.infile) do |fi|
File.open(usage.outfile, "w") do |fo|
fo.write(fi.read)
end
end
If the user doesn't supply the correct number of arguments, the program
exits with an error
and the usage for the program (hence the libraries name).
PROGRAM: test.rb
ERROR: too few arguments 2 expected, 0 given
USAGE: test.rb infile outfile
2. Lists of files (...)
You can write a program that accepts a list of files by using elipses
appended to an
argument (the following program concatenates the input files into one
output file).
usage = Usage.new "outfile infiles..."
File.open(usage.outfile, "w") do |fo|
usage.infiles.each do |infile|
File.open(usage.infile) { |fi| fo.write(fi.read)}
end
end
3. Optional arguments
You can have optional arguments by surounding them in square brackets.
usage = Usage.new "required_arg [optional_arg] "
These are accessed in the standard way
usage.optional_arg # this is nil if it is not given by the user
usage.required_arg
4. Options
You can have dash options that are either required or optional. Options
can also have
arguments associated with them.
usage = Usage.new "[-y] [-x excluded_tags] (-z ztag) (-w
warning_arg) files..."
The options are accessed with "dash_" prefixing the option so that the
-y is accessed
via .dash_y. The -x can be accessed either with #dash_x (which would be
either nil or
true) or #excluded_tags (which would be either nil or the argument for
the -x option).
The -z option is required and has one argument, also the -w option is
also required.
They can appear in any order (-z option first or -w option first). The
optional arguments
can appear either before, interspersed with, or after the required options.
5. Long Options
You can also have long options by including lines following the initial
usage line that
associates the short options with the long ones. Example below:
usage = Usage.new "-x files...", <<EOT
-x,--exclusive specifies exclusive access to the files
EOT
With this case, now #dash_x and #exclusive give the same result when
applied to the usage
variable.
6. Typed options
In order to remove a step and improve argument checking, you can also
add in a "type"
character to identify its type. The characters I used are somewhat
arbitrary. Some of
them I took from BASIC which I programmed in long long ago.
% - Integer
$ - String (but this is unnecessary as this is default)
# - Float
@ - Date-Time
So when you send the argument message to the usage object, you will get
a value of that
type and if the user does not give that type, then they get an error
message.
usage = Usage.new "%num_times @on_date"
In this example, #num_times returns and Integer object and #on_date
returns a Time object.
7. Choice options
You can have optional options that have a set of values which they can
be. The choices
are separated by pipe symbols. See below:
usage = Usage.new "[-a coffee|tea|milk]"
After this #dash_a will give the string coffee, tea, or milk. If the
value given isn't
one of the given choices, then the user is given an error message with the
appropriate choices.
Steve Tuckner
