Introduction

In order to implement a tamperproof command line parsing, one usually has to write a significant amount of code. Using GetPot allows to shrink code fragments such as

...
   int     i = 0;
   double  v = 0;
   char*   endptr = 0;
...
   if( i < argc ) {
       v = strtod(argv[i], &endptr);
       if( endptr == argv[i] ) // argv[i] was not a number
          v = 9.81;            // set default value
   }
...

to a single line

    const double V = cl.get(i, 9.81);

In fact, GetPot allows you to do much more sophisticated things in not more than one single program line. Additionally, GetPot provides a parser to handle input files such as 'example.pot':

...
   webpage  = http://getpot.sourceforge.net/GetPot.html
   user     = 'G. V. V. Bouche'     # whitespace requires quotes
   clicks   = 231   # [1/s]
   factor_x = 1.231 # [m/s^2]

   [vehicle]
   wheel-base  = 2.65             # [m]
   initial-xyz = '100.  0.1  5.0' # [m]
...

and read out its contents in the same way the command line was parsed. There are a few special things to know. In some aspects parsing input files differs from parsing the command line.