Command Prompt arguments.

DanDan has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I'm new to Perl and so I'm just starting to understand its power. I'm trying to run a perl script so that users can call it and pass certain arguments in. e.g. ascript -d db1 -i inst1 or ascript -ddb1 -i inst1 My solution is okay but as I'm trying to get a feel of perl I'm guessing there is a better way. ( A case of right answer but probably not best perl solution). I'm after advice really and getting into the perl programmers frame of mind rather than a C developer.

   ... cut ...
   my $str_arg = join " ",@ARGV;
   #remove spaces
   $str_arg =~ s/\s//g;
   @args= split /-/, $str_arg;
   shift @args;

   for my $arg (@args)
   {
      my $opt = substr($arg,0,1);

      switch ($opt)
      {
     case /d/
     { 
        #this is taking the value off.
        $options{$opt}=$arg;
        print "This is a database $options{$opt}\n";
     }
     case /i/
     { 
        $options{$opt}=$arg;
        print "This is an instance $options{$opt}\n";
     }
     else
     {
        print "Error arg not recognised!!!\n";
     }
      }       
   }
[download]

Thanks, DanDan Thanks for all your great help... The solutions and ideas and pointers are spot on. Thanks, DanDan.

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Re: Command Prompt arguments. by slife (Scribe) on Jun 21, 2004 at 11:50 UTC
DanDan, welcome to the Perl community. Others have already pointed out that there are several modules available that handle command line options. However, since you describe yourself as both a Perl novice and a C-programmer, here are some comments that I hope will be helpful: Use Super Search to see similar discussions, e.g. at How to pass and retrieve command-line arguments specifying search conditions?. Always begin your programs with 'use strict' and 'use warnings'. This will eliminate at stroke many hours of frustration. Perl has no build-in switch or case statements. If you have a copy of Programming Perl 3rd edition to hand, Ch4 pp124-125 suggests some 'Perl-ish' alternatives. See also What is the most efficient perl switch/case statement?. Again from PP 3rd ed, p589 has a list of common traps for C programmers new to Perl. This info also appears in perldoc perltrap.	[reply]
Re^2: Command Prompt arguments. by hmerrill (Friar) on Jun 21, 2004 at 12:34 UTC
Excellent recommendations! I'll just add a few things. If you're not familiar with the excellent documentation that is included with perl, it's called the 'perldocs'. You can get started by doing 'perldoc perl' at a command prompt. As far as books are concerned, I would also highly recommend 'Programming Perl' 3rd edition. And high on my list are 'Learning Perl' and 'Perl Cookbook'. HTH.	[reply]
Re^3: Command Prompt arguments. by slife (Scribe) on Jun 21, 2004 at 12:54 UTC
Peter Scott's "Perl Medic" seems to be well-regarded, though I haven't read it myself (yet): Perl Medic: Transforming Legacy Code by Peter J. Scott	[reply]
Re: Command Prompt arguments. by borisz (Canon) on Jun 21, 2004 at 10:54 UTC
There are some modules that handle that for you. See Getopt::Long or Getopt::Std. Boris	[reply]
Re: Command Prompt arguments. by eserte (Deacon) on Jun 21, 2004 at 10:56 UTC
Usually you should use one of the Getopt:: modules. Here's the solution with Getopt::Long (untested): `use Getopt::Long; GetOptions(\%opt, "d=s", "i=s") or die "usage..."; # the options are now in $opt{d} and $opt{i}` [download]	[reply] [d/l]
Re: Command Prompt arguments. by husker (Chaplain) on Jun 21, 2004 at 15:18 UTC
For what you are doing, I recommend Getopt::Std. In fact, this recent Code I posted uses Getopt::Std for some required and optional command-line arguments. Hope it's illustrative for you. _{Edit: Added link to example code.}	[reply]