Command Line Arguments with Getopt::Long

Command Line Arguments with Getopt::Long

• 1.
  Command Line Arguments withGetopt::Long By Ian Kluft Part of short Lightning Talks session Silicon Valley Perl November 12, 2015 Santa Clara, California
• 2.
  Command-Line Arguments ● Manyprograms use command line interface – Software builds – Automated tools – Experimental calculations – Anything there isn't time to make a GUI ● Don't write new code to process CLI arguments – Standards compliance comes with Getopt::Long – It's in CPAN
• 3.
  Getopt::Long usage (1of 2) From the manpage: use Getopt::Long;       my $data   = "file.dat";       my $length = 24;       my $verbose;       GetOptions ("length=i" => $length,    # numeric                   "file=s"   => $data,      # string                   "verbose"  => $verbose)   # flag       or die("Error in command line argumentsn"); ● Note these things: ● Getopt::Long and its function GetOptions ● Initialization of variables before using them ● Specification and destination variable pairs
• 4.
  Getopt::Long usage (2of 2) ● GetOptions processes the command line ● It removes the Unix-standard CLI options – Like --optname, --optname=value, etc – Single dash prefixes single-character options – These can be in any order ● It leaves everything else in @ARGV list – Such as filenames or text – Whatever you use them for
• 5.
  Option specifications (1of 2) ● GetOptions takes specification/destination pairs – Specification: name/format of argument – Destination: reference to variable to store data ● Boolean – GetOptions ( “flag” => $flag ); – Stores true (1) if --flag is present – With “!flag”, it stores false if --noflag is present – $flag is not modified if --flag is not present ● So don't forget to initialize it!
• 6.
  Option specifications (2of 2) ● GetOptions ( “stringarg=s” => $stringarg ); – Use “=s” for mandatory string argument – Use “:s” for optional string argument ● GetOptions ( “integerarg=i” => $integerarg ); – Use “=i” for mandatory integer argument – Use “:i” for optional integer argument ● GetOptions ( “floatarg=f” => $floatarg ); – Use “=f” for mandatory floating point argument – Use “:f” for optional floating point argument
• 7.
  Lists from arguments ●GetOptions ("library=s" => @libfiles); – Multiple occurrences of --library go in @libfiles ● GetOptions ("library=s@" => $libfiles); – Same thing, but $libfiles is a reference to an array ● Example: use the argument more than once – prog --library lib/stdlib --library lib/extlib
• 8.
  Hashes from arguments ●GetOptions ("define=s" => %defines); – key=value pair is placed in %defines hash ● GetOptions ("define=s%" => $defines); – Same thing, except $defines is a ref to a hash ● Example: – prog --define os=linux --define vendor=redhat
• 9.
  Similar CPAN modules ●Getopt::LL – wider set of prcoessing rules ● Getopt::XML – read XML in Getopt::Long style ● MooseX::Getopt – Getopt for Moose ● Many other smaller modules – Search CPAN for “Getopt”