3. Argument Types
What kinds of arguments to expect?
-xyz toggle switch
-xyz 17 value
-xyz=17 value (parsing)
-wx combined (-w –x)
-x 17 24 list
--x turn off
--long double dash
value bare value
-- end of arguments
Where are the arguments?
@ARGV
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4. Criteria for Solution?
What do we want a solution to
accomplish?
• Easy to use
• Argument validation
• integers
• file names
• Self-documenting
• Usage statement (help)
• Flexible
• Powerful
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5. Do It Yourself
Handle arguments manually
while (@ARGV)
{ my $argv = shift(@ARGV);
if ($argv =~ /^-x$/){$x=1;next}
if ($argv =~ /^-y$/)
{ $y = shift(@ARGV)
or die;
next; }
if ($argv =~ /^--$/) { last } # stop
push @files, $argv;
}
@ARGV = (@files, @ARGV);
while (<>)
{ do something here }
Pros: full control
Cons: tedious, check arguments manually
documentation?
extensibility?
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6. -s Option
Perl has a builtin option for basic
argument handling: -s
In the script, use it on the shebang line:
#!/usr/local/bin/perl –s
…enabling this behavior:
Option Variables
-xyz $xyz = 1
-xyz=blue $xyz = “blue”
Pros: easy
Cons: documentation?
shebang
combined options?
check arguments manually
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7. Getopt::Long
use Getopt::Long;
my $data = "file.dat";
my $length = 24;
my $verbose;
$result = GetOptions
(
"length=i" => $length, # numeric
"file=s" => $data, # string
"verbose" => $verbose # flag
);
Pros: argument checking
Cons: 24 pages of docs for G:L
script documentation?
wordy
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8. Getopt::Declare
use Getopt::Declare;
my $spec = qq{
[nocase] # case insenstive options
-in <in:if> input file
-out <out:of> output file
[mutex –in –out]
-off <offset:i> offset (int)
-b[ells+]w[histles] -bw also works
{ $::BELLS = 1; } }
my $options = Getopt::Declare->new($spec);
Pros: Functionality!
Spec is usage
Argument checking
Full Parser!
Cons: Functionality!
32 pages of docs for G:D!
Subtle gotchas (like [])
Object oriented (more work?)
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