/*----------------------------------------------------------------------
  File    : skeleton.c
  Contents: command line program skeleton
  Author  : Christian Borgelt
  History : 11.11.1997 file created from skel1.c
            16.02.1999 argument evaluation improved
----------------------------------------------------------------------*/
#define _POSIX_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>

/*----------------------------------------------------------------------
  Preprocessor Definitions
----------------------------------------------------------------------*/
/* --- error codes --- */
#define OK            0         /* no error */
#define E_NONE        0         /* no error */
#define E_NOMEM     (-1)        /* not enough memory */
#define E_FOPEN     (-2)        /* file open failed */
#define E_FREAD     (-3)        /* file read failed */
#define E_FWRITE    (-4)        /* file write failed */
#define E_OPTION    (-5)        /* unknown option */
#define E_OPTARG    (-6)        /* missing option argument */
#define E_ARGCNT    (-7)        /* wrong number of arguments */
#define E_UNKNOWN   (-8)        /* unknown error */

/*----------------------------------------------------------------------
  Constants
----------------------------------------------------------------------*/
const char *errmsgs[] = {       /* error messages */
  /* E_NONE      0 */  "no error\n",
  /* E_NOMEM    -1 */  "not enough memory\n",
  /* E_FOPEN    -2 */  "cannot open file `%s'\n",
  /* E_FREAD    -3 */  "read error on file `%s'\n",
  /* E_FWRITE   -4 */  "write error on file `%s'\n",
  /* E_OPTION   -5 */  "unknown option -%c\n",
  /* E_OPTARG   -6 */  "missing option argument\n",
  /* E_ARGCNT   -7 */  "wrong number of arguments\n",
  /* E_UNKNOWN  -8 */  "unknown error\n"
};

/*----------------------------------------------------------------------
  Global Variables
----------------------------------------------------------------------*/
static char *prgname;           /* program name for error messages */

/*----------------------------------------------------------------------
  Functions
----------------------------------------------------------------------*/

static void error (int code, ...)
{                               /* --- print error message */
  va_list    args;              /* list of variable arguments */
  const char *msg;              /* buffer for error message */

  if ((code > 0) || (code < E_UNKNOWN))
    code = E_UNKNOWN;           /* check error code */
  msg = errmsgs[-code];         /* get error message */
  if (!msg) msg = errmsgs[-E_UNKNOWN];
  fprintf(stderr, "\n%s: ", prgname);  /* print program name */
  va_start(args, code);         /* get variable arguments */
  vfprintf(stderr, msg, args);  /* print error message */
  va_end(args);                 /* end variable argument evaluation */

  /* >>> clean up code goes here <<< */

  exit(code);                   /* abort programm */
}  /* error() */

/*--------------------------------------------------------------------*/

int main (int argc, char *argv[])
{                               /* --- main function */
  int    i, k = 0;              /* loop variables, counters */
  char   *s;                    /* to traverse options */
  char   **optarg = NULL;       /* option argument */
  int    flag     = 0;          /* an optional switch */
  int    intnum   = 0;          /* an optional integer */
  double fltnum   = 0.0;        /* an optional float */
  char   *string  = "default";  /* an optional string */
  char   *arg1    = NULL;       /* fixed argument 1 */
  char   *arg2    = NULL;       /* fixed argument 2 */

  prgname = argv[0];            /* get program name for error msgs. */

  /* --- print startup/usage message --- */
  if (argc > 1) {               /* if arguments given */
    printf("%s - command line program skeleton", argv[0]);
    fflush(stdout); }           /* print startup message */
  else {                        /* if no argument given */
    printf("usage: %s [options] arg1 arg2\n", argv[0]);
    printf("-g     sets   an optional flag    in the program\n");
    printf("-i#    passes an optional integer to the program\n");
    printf("-f#    passes an optional float   to the program\n");
    printf("-s#    passes an optional string  to the program\n");
    printf("arg?   fixed arguments\n");
    return 0;                   /* print a usage message */
  }                             /* and abort the program */

  /* --- evaluate arguments --- */
  for (i = 1; i < argc; i++) {  /* traverse arguments */
    s = argv[i];                /* get option argument */
    if (optarg) { *optarg = s; optarg = NULL; continue; }
    if (*s == '-') {            /* -- if argument is an option */
      if (!*++s) error(E_OPTION, ' ');
      while (1) {               /* traverse characters */
        switch (*s++) {         /* evaluate option */
          case 'g': flag   = 1;                      break;
          case 'i': intnum = (int)strtol(s, &s, 10); break;
          case 'f': fltnum = strtod(s, &s);          break;
  	  case 's': optarg = &string;                break;
          default : error(E_OPTION, *(--s));         break;
        }                       /* set option variables */
        if (!*s) break;         /* if at end of string, abort loop */
        if (optarg) { *optarg = s; optarg = NULL; break; }
      } }                       /* get option argument */
    else {                      /* -- if argument is no option */
      switch (k++) {            /* evaluate non-option */
        case  0: arg1 = argv[i];  break;
        case  1: arg2 = argv[i];  break;
        default: error(E_ARGCNT); break;
      }                         /* note fixed arguments */
    }
  }
  if (optarg) error(E_OPTARG);  /* check option argument */
  if (k != 2) error(E_ARGCNT);  /* check number of arguments */
  printf("\n");                 /* terminate startup message */

  /* >>> application specific code goes here <<< */
  printf("flag  : %d\n", flag);
  printf("intnum: %d\n", intnum);
  printf("fltnum: %f\n", fltnum);
  printf("string: %s\n", string);
  printf("arg1  : %s\n", arg1);
  printf("arg2  : %s\n", arg2);

  return 0;                     /* return 'ok' */
}  /* main() */